Support exporting python dependency metadata

Makefile

@@ -73,11 +73,11 @@ serve: $(WASM_FILE)
 
 # Test all examples (requires all WASM files to be built)
 test: $(COMPOSED_WASMS)
-	VICEROY=$(VICEROY) uv run --extra test pytest
+	VICEROY=$(VICEROY) FASTLY_COMPUTE_PY="$(FASTLY_COMPUTE_PY)" uv run --extra test pytest
 
 # Update snapshots for snapshot tests
 test-update-snapshots: $(COMPOSED_WASMS)
-	VICEROY=$(VICEROY) uv run --extra test pytest --snapshot-update
+	VICEROY=$(VICEROY) FASTLY_COMPUTE_PY="$(FASTLY_COMPUTE_PY)" uv run --extra test pytest --snapshot-update
 
 # List available examples
 list-examples:

crates/fastly-compute-py/Cargo.toml

@@ -29,6 +29,7 @@ componentize-py = { git = "https://github.com/bytecodealliance/componentize-py",
 futures = { version = "0.3", default-features = false, features = ["executor"] }
 pyo3 = { version = "0.28.3", features = ["abi3-py312"], optional = true }
 serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
 toml = "0.8"
 log = "0.4"
 env_logger = "0.11"

crates/fastly-compute-py/build.rs

@@ -12,7 +12,8 @@ fn main() -> Result<()> {
  println!("cargo:rerun-if-changed=../../wrap_app_in_wasiless.wac");
  println!("cargo:rerun-if-changed=../../Cargo.lock");
 
- let root_dir = PathBuf::from("../../");
+ let manifest_dir = env::var("CARGO_MANIFEST_DIR").expect("Failed to get CARGO_MANIFEST_DIR");
+ let root_dir: PathBuf = [&manifest_dir, "..", ".."].iter().collect();
  let wit_dir = root_dir.join("wit");
  let out_dir = PathBuf::from(env::var("OUT_DIR")?);
 

crates/fastly-compute-py/src/cli.rs

@@ -36,7 +36,6 @@ pub enum Command {
  #[arg(short, long)]
  virtualenv: Option<PathBuf>,
  },
-
  /// Generate WIT binding stubs for use with type checkers and IDEs
  Bindings {
  /// WIT directory to generate bindings from (default: wit)
@@ -54,4 +53,26 @@ pub enum Command {
  /// Output directory for the generated stubs
  output_dir: PathBuf,
  },
+ /// List project dependencies in the specified format
+ Dependencies {
+ /// Output format for dependencies
+ #[arg(short, long, default_value = "json")]
+ format: DependencyFormat,
+
+ /// Write output to this file instead of stdout
+ #[arg(short, long)]
+ output: Option<PathBuf>,
+
+ /// Virtual environment in which to look for modules (default:
+ /// VIRTUAL_ENV env var or .venv)
+ #[arg(short, long)]
+ virtualenv: Option<PathBuf>,
+ },
+}
+
+#[derive(Clone, Debug, clap::ValueEnum)]
+pub enum DependencyFormat {
+ /// JSON object format: {"package-name": "1.0.0", ...}
+ /// Matches the format used in fastly_data metadata
+ Json,
 }

crates/fastly-compute-py/src/config.rs

@@ -75,6 +75,7 @@ impl ConfigBuilder {
  self.cli.virtualenv = virtualenv.clone();
  }
  Command::Bindings { .. } => {}
+ Command::Dependencies { .. } => {}
  }
  self
  }

crates/fastly-compute-py/src/dependencies.rs

@@ -0,0 +1,198 @@
+use anyhow::{Context, Result};
+use serde::{Deserialize, Serialize};
+use std::collections::HashMap;
+use std::path::PathBuf;
+use std::process::Command;
+
+/// A single package dependency with name and version
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct Dependency {
+ pub name: String,
+ pub version: String,
+}
+
+/// Fastly CLI DataCollection format for fastly_data metadata.
+/// Matches the Go structs in pkg/commands/compute/build.go.
+#[derive(Debug, Serialize)]
+pub struct FastlyData {
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub package_info: Option<PackageInfo>,
+}
+
+#[derive(Debug, Serialize)]
+pub struct PackageInfo {
+ pub packages: HashMap<String, String>,
+}
+
+/// PEP 751 pylock.toml format structures
+#[derive(Debug, Deserialize)]
+struct PylockToml {
+ #[serde(rename = "lock-version")]
+ _lock_version: String,
+ packages: Vec<PylockPackage>,
+}
+
+#[derive(Debug, Deserialize)]
+struct PylockPackage {
+ name: String,
+ /// Present for registry/VCS packages; absent for local source trees
+ /// (PEP 751: version MUST NOT be included when using a source tree)
+ version: Option<String>,
+}
+
+/// Get dependencies using UV's PEP 751 export.
+///
+/// Dependency collection only runs when both conditions are met:
+///
+/// 1. A `pyproject.toml` exists in the current directory — confirming this is
+/// a Python project that could have a lockfile. Without this, `uv export`
+/// would fail with "no pyproject.toml found" (e.g. the Viceroy test
+/// framework builds in a temp dir with no project files).
+///
+/// 2. The `UV` environment variable is set — confirming the tool was invoked
+/// via `uv run` or similar. We don't guess that `uv` should be used just
+/// because a `uv` binary happens to be on PATH; the user may be using pip,
+/// poetry, or another tool entirely.
+///
+/// When both conditions are met, errors from `uv export` are bubbled up since
+/// something genuinely went wrong in a context where UV is expected to work.
+pub fn get_dependencies(_virtualenv: &Option<PathBuf>) -> Result<Vec<Dependency>> {
+ if !std::fs::exists("pyproject.toml").unwrap_or_default() {
+ log::debug!("No pyproject.toml found, skipping dependency collection");
+ return Ok(Vec::new());
+ }
+
+ let uv_bin = match std::env::var("UV") {
+ Ok(bin) => bin,
+ Err(_) => {
+ log::debug!("UV env var not set, skipping dependency collection");
+ return Ok(Vec::new());
+ }
+ };
+
+ log::info!("Collecting dependencies from project environment...");
+
+ let deps = get_dependencies_from_uv(&uv_bin)?;
+ log::info!("Found {} dependencies via UV", deps.len());
+ Ok(deps)
+}
+
+/// Serialize dependencies as fastly_data JSON, matching the CLI's DataCollection format.
+///
+/// The build tool injects this directly so the CLI does not need to know anything
+/// about the Python environment to collect package metadata.
+pub fn get_fastly_data_json(virtualenv: &Option<PathBuf>) -> Result<String> {
+ let deps = get_dependencies(virtualenv)?;
+
+ if deps.is_empty() {
+ return Ok(String::new());
+ }
+
+ let packages: HashMap<String, String> = deps.into_iter().map(|d| (d.name, d.version)).collect();
+
+ let fastly_data = FastlyData {
+ package_info: Some(PackageInfo { packages }),
+ };
+
+ serde_json::to_string(&fastly_data).context("Failed to serialize fastly_data to JSON")
+}
+
+/// Use UV export to get dependencies in PEP 751 pylock.toml format
+fn get_dependencies_from_uv(uv_bin: &str) -> Result<Vec<Dependency>> {
+ log::debug!(
+ "Attempting to export dependencies using UV binary: {}",
+ uv_bin
+ );
+
+ let output = Command::new(uv_bin)
+ .args([
+ "export",
+ "--format",
+ "pylock.toml",
+ "--no-emit-project",
+ "--frozen",
+ "--no-header",
+ ])
+ .output()
+ .context("Failed to run 'uv export'")?;
+
+ if !output.status.success() {
+ let stderr = String::from_utf8_lossy(&output.stderr);
+ anyhow::bail!("uv export failed: {}", stderr);
+ }
+
+ let pylock_content =
+ String::from_utf8(output.stdout).context("UV output was not valid UTF-8")?;
+
+ parse_pylock_toml(&pylock_content)
+}
+
+/// Parse PEP 751 pylock.toml format
+fn parse_pylock_toml(content: &str) -> Result<Vec<Dependency>> {
+ let pylock: PylockToml =
+ toml::from_str(content).context("Failed to parse pylock.toml format")?;
+
+ let dependencies = pylock
+ .packages
+ .into_iter()
+ .map(|pkg| Dependency {
+ version: pkg.version.unwrap_or_else(|| "unknown".to_string()),
+ name: pkg.name,
+ })
+ .collect();
+
+ Ok(dependencies)
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+
+ #[test]
+ fn test_parse_versioned_packages() {
+ let sample = r#"
+lock-version = "1.0"
+created-by = "uv"
+requires-python = ">=3.12"
+
+[[packages]]
+name = "bottle"
+version = "0.13.4"
+
+[[packages]]
+name = "requests"
+version = "2.31.0"
+"#;
+
+ let deps = parse_pylock_toml(sample).unwrap();
+ assert_eq!(deps.len(), 2);
+ assert_eq!(deps[0].name, "bottle");
+ assert_eq!(deps[0].version, "0.13.4");
+ assert_eq!(deps[1].name, "requests");
+ assert_eq!(deps[1].version, "2.31.0");
+ }
+
+ #[test]
+ fn test_parse_directory_dependency_uses_unknown() {
+ // PEP 751: version MUST NOT be included for source trees.
+ // We record "unknown" so the dependency is still visible.
+ let sample = r#"
+lock-version = "1.0"
+created-by = "uv"
+requires-python = ">=3.12"
+
+[[packages]]
+name = "bottle"
+version = "0.13.4"
+
+[[packages]]
+name = "fastly-compute"
+directory = { path = "../../", editable = true }
+"#;
+
+ let deps = parse_pylock_toml(sample).unwrap();
+ assert_eq!(deps.len(), 2);
+ assert_eq!(deps[1].name, "fastly-compute");
+ assert_eq!(deps[1].version, "unknown");
+ }
+}

crates/fastly-compute-py/src/lib.rs

@@ -14,6 +14,7 @@ use wasm_metadata::AddMetadata;
 
 pub mod cli;
 pub mod config;
+pub mod dependencies;
 pub mod site_packages;
 
 use cli::Cli;
@@ -113,6 +114,34 @@ pub fn run_main(cli: &Cli) -> Result<()> {
  output_dir,
  )?;
  }
+ cli::Command::Dependencies {
+ format,
+ output,
+ virtualenv,
+ } => {
+ let deps = dependencies::get_dependencies(virtualenv)?;
+
+ match format {
+ cli::DependencyFormat::Json => {
+ // Convert to HashMap matching fastly_data packages format
+ let mut packages = std::collections::HashMap::new();
+ for dep in deps {
+ packages.insert(dep.name, dep.version);
+ }
+
+ let json = serde_json::to_string_pretty(&packages)
+ .context("Failed to serialize dependencies to JSON")?;
+
+ match output {
+ Some(path) => {
+ fs::write(path, &json)
+ .context("Failed to write dependencies to output file")?;
+ }
+ None => println!("{}", json),
+ }
+ }
+ }
+ }
  }
 
  Ok(())
@@ -223,7 +252,7 @@ pub fn build(output: PathBuf, entry_name: String, virtualenv: Option<PathBuf>) -
  compose_with_wasiless(&temp_component_wasm_path, WASILESS_WASM, WRAP_WAC, &output)?;
 
  log::info!(" Injecting Fastly metadata...");
- let annotated = inject_fastly_metadata(composed)?;
+ let annotated = inject_fastly_metadata(composed, &virtualenv)?;
 
  fs::write(&output, annotated)
  .with_context(|| format!("Failed to write output: {}", output.display()))?;
@@ -302,16 +331,18 @@ fn compose_with_wasiless(
 /// - `processed-by: componentize-py <version>` — the tool that performed the
 /// core Wasm transformation. `fastly-compute-py` also adds itself here as
 /// the build orchestrator.
+/// - `processed-by: fastly_data` — package dependency list in the same JSON
+/// format the Fastly CLI uses for all other languages. The CLI merges its
+/// own fields (build_info, machine_info, script_info) on top and skips
+/// re-collecting package_info when this key is already present.
 ///
 /// Note: the Fastly-proprietary `fastly.manifest.*` custom sections
 /// (language, version, service_id, etc.) are **not** written here. Those are
 /// injected during package ingestion, sourced from the `fastly.toml` manifest
 /// that the CLI bundles alongside the Wasm in the upload package.
-/// Dependency lists, build scripts, and machine info are similarly the CLI's
-/// responsibility via its `fastly_data` producers entry.
 ///
 /// [Producers Section spec]: https://github.com/WebAssembly/tool-conventions/blob/main/ProducersSection.md
-fn inject_fastly_metadata(wasm: Vec<u8>) -> Result<Vec<u8>> {
+fn inject_fastly_metadata(wasm: Vec<u8>, virtualenv: &Option<PathBuf>) -> Result<Vec<u8>> {
  let mut add_metadata = AddMetadata::default();
 
  // Source language. The version is the CPython version bundled by
@@ -337,6 +368,19 @@ fn inject_fastly_metadata(wasm: Vec<u8>) -> Result<Vec<u8>> {
  env!("CARGO_PKG_VERSION").to_owned(),
  ));
 
+ // Inject dependencies as fastly_data, matching the format the Fastly CLI
+ // writes for other languages. The CLI merges its own fields on top and
+ // skips re-collecting package_info when this key is already present.
+ let fastly_data_json = dependencies::get_fastly_data_json(virtualenv)?;
+ if !fastly_data_json.is_empty() {
+ log::debug!("Injecting fastly_data with package dependencies");
+ add_metadata
+ .processed_by
+ .push(("fastly_data".to_owned(), fastly_data_json));
+ } else {
+ log::debug!("No dependencies found to inject");
+ }
+
  add_metadata
  .to_wasm(&wasm)
  .context("Failed to add producers metadata to Wasm component")

fastly_compute/runtime_patching/patches.py

@@ -40,7 +40,8 @@
  # the wit_world, is around.
  def patch():
  """Pretend to patch."""
- print("Faking the run of exception-mapping monkeypatches for test runner.")
+ import sys
+ print("Faking the run of exception-mapping monkeypatches for test runner.", file=sys.stderr)
 else:
  MAPPINGS = {
  wit_world.imports.acl.AclError.GENERIC_ERROR: fastly_compute.exceptions.acl.acl_error.GenericError,

Makefile

@@ -73,11 +73,11 @@ serve: $(WASM_FILE)
 
 # Test all examples (requires all WASM files to be built)
 test: $(COMPOSED_WASMS)
-	VICEROY=$(VICEROY) uv run --extra test pytest
+	VICEROY=$(VICEROY) FASTLY_COMPUTE_PY="$(FASTLY_COMPUTE_PY)" uv run --extra test pytest
 
 # Update snapshots for snapshot tests
 test-update-snapshots: $(COMPOSED_WASMS)
-	VICEROY=$(VICEROY) uv run --extra test pytest --snapshot-update
+	VICEROY=$(VICEROY) FASTLY_COMPUTE_PY="$(FASTLY_COMPUTE_PY)" uv run --extra test pytest --snapshot-update
 
 # List available examples
 list-examples:

crates/fastly-compute-py/Cargo.toml

@@ -29,6 +29,7 @@ componentize-py = { git = "https://github.com/bytecodealliance/componentize-py",
 futures = { version = "0.3", default-features = false, features = ["executor"] }
 pyo3 = { version = "0.28.3", features = ["abi3-py312"], optional = true }
 serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
 toml = "0.8"
 log = "0.4"
 env_logger = "0.11"

crates/fastly-compute-py/build.rs

@@ -12,7 +12,8 @@ fn main() -> Result<()> {
  println!("cargo:rerun-if-changed=../../wrap_app_in_wasiless.wac");
  println!("cargo:rerun-if-changed=../../Cargo.lock");
 
- let root_dir = PathBuf::from("../../");
+ let manifest_dir = env::var("CARGO_MANIFEST_DIR").expect("Failed to get CARGO_MANIFEST_DIR");
+ let root_dir: PathBuf = [&manifest_dir, "..", ".."].iter().collect();
  let wit_dir = root_dir.join("wit");
  let out_dir = PathBuf::from(env::var("OUT_DIR")?);
 

crates/fastly-compute-py/src/cli.rs

@@ -36,7 +36,6 @@ pub enum Command {
  #[arg(short, long)]
  virtualenv: Option<PathBuf>,
  },
-
  /// Generate WIT binding stubs for use with type checkers and IDEs
  Bindings {
  /// WIT directory to generate bindings from (default: wit)
@@ -54,4 +53,26 @@ pub enum Command {
  /// Output directory for the generated stubs
  output_dir: PathBuf,
  },
+ /// List project dependencies in the specified format
+ Dependencies {
+ /// Output format for dependencies
+ #[arg(short, long, default_value = "json")]
+ format: DependencyFormat,
+
+ /// Write output to this file instead of stdout
+ #[arg(short, long)]
+ output: Option<PathBuf>,
+
+ /// Virtual environment in which to look for modules (default:
+ /// VIRTUAL_ENV env var or .venv)
+ #[arg(short, long)]
+ virtualenv: Option<PathBuf>,
+ },
+}
+
+#[derive(Clone, Debug, clap::ValueEnum)]
+pub enum DependencyFormat {
+ /// JSON object format: {"package-name": "1.0.0", ...}
+ /// Matches the format used in fastly_data metadata
+ Json,
 }

crates/fastly-compute-py/src/config.rs

@@ -75,6 +75,7 @@ impl ConfigBuilder {
  self.cli.virtualenv = virtualenv.clone();
  }
  Command::Bindings { .. } => {}
+ Command::Dependencies { .. } => {}
  }
  self
  }

crates/fastly-compute-py/src/dependencies.rs

@@ -0,0 +1,198 @@
+use anyhow::{Context, Result};
+use serde::{Deserialize, Serialize};
+use std::collections::HashMap;
+use std::path::PathBuf;
+use std::process::Command;
+
+/// A single package dependency with name and version
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct Dependency {
+ pub name: String,
+ pub version: String,
+}
+
+/// Fastly CLI DataCollection format for fastly_data metadata.
+/// Matches the Go structs in pkg/commands/compute/build.go.
+#[derive(Debug, Serialize)]
+pub struct FastlyData {
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub package_info: Option<PackageInfo>,
+}
+
+#[derive(Debug, Serialize)]
+pub struct PackageInfo {
+ pub packages: HashMap<String, String>,
+}
+
+/// PEP 751 pylock.toml format structures
+#[derive(Debug, Deserialize)]
+struct PylockToml {
+ #[serde(rename = "lock-version")]
+ _lock_version: String,
+ packages: Vec<PylockPackage>,
+}
+
+#[derive(Debug, Deserialize)]
+struct PylockPackage {
+ name: String,
+ /// Present for registry/VCS packages; absent for local source trees
+ /// (PEP 751: version MUST NOT be included when using a source tree)
+ version: Option<String>,
+}
+
+/// Get dependencies using UV's PEP 751 export.
+///
+/// Dependency collection only runs when both conditions are met:
+///
+/// 1. A `pyproject.toml` exists in the current directory — confirming this is
+/// a Python project that could have a lockfile. Without this, `uv export`
+/// would fail with "no pyproject.toml found" (e.g. the Viceroy test
+/// framework builds in a temp dir with no project files).
+///
+/// 2. The `UV` environment variable is set — confirming the tool was invoked
+/// via `uv run` or similar. We don't guess that `uv` should be used just
+/// because a `uv` binary happens to be on PATH; the user may be using pip,
+/// poetry, or another tool entirely.
+///
+/// When both conditions are met, errors from `uv export` are bubbled up since
+/// something genuinely went wrong in a context where UV is expected to work.
+pub fn get_dependencies(_virtualenv: &Option<PathBuf>) -> Result<Vec<Dependency>> {
+ if !std::fs::exists("pyproject.toml").unwrap_or_default() {
+ log::debug!("No pyproject.toml found, skipping dependency collection");
+ return Ok(Vec::new());
+ }
+
+ let uv_bin = match std::env::var("UV") {
+ Ok(bin) => bin,
+ Err(_) => {
+ log::debug!("UV env var not set, skipping dependency collection");
+ return Ok(Vec::new());
+ }
+ };
+
+ log::info!("Collecting dependencies from project environment...");
+
+ let deps = get_dependencies_from_uv(&uv_bin)?;
+ log::info!("Found {} dependencies via UV", deps.len());
+ Ok(deps)
+}
+
+/// Serialize dependencies as fastly_data JSON, matching the CLI's DataCollection format.
+///
+/// The build tool injects this directly so the CLI does not need to know anything
+/// about the Python environment to collect package metadata.
+pub fn get_fastly_data_json(virtualenv: &Option<PathBuf>) -> Result<String> {
+ let deps = get_dependencies(virtualenv)?;
+
+ if deps.is_empty() {
+ return Ok(String::new());
+ }
+
+ let packages: HashMap<String, String> = deps.into_iter().map(|d| (d.name, d.version)).collect();
+
+ let fastly_data = FastlyData {
+ package_info: Some(PackageInfo { packages }),
+ };
+
+ serde_json::to_string(&fastly_data).context("Failed to serialize fastly_data to JSON")
+}
+
+/// Use UV export to get dependencies in PEP 751 pylock.toml format
+fn get_dependencies_from_uv(uv_bin: &str) -> Result<Vec<Dependency>> {
+ log::debug!(
+ "Attempting to export dependencies using UV binary: {}",
+ uv_bin
+ );
+
+ let output = Command::new(uv_bin)
+ .args([
+ "export",
+ "--format",
+ "pylock.toml",
+ "--no-emit-project",
+ "--frozen",
+ "--no-header",
+ ])
+ .output()
+ .context("Failed to run 'uv export'")?;
+
+ if !output.status.success() {
+ let stderr = String::from_utf8_lossy(&output.stderr);
+ anyhow::bail!("uv export failed: {}", stderr);
+ }
+
+ let pylock_content =
+ String::from_utf8(output.stdout).context("UV output was not valid UTF-8")?;
+
+ parse_pylock_toml(&pylock_content)
+}
+
+/// Parse PEP 751 pylock.toml format
+fn parse_pylock_toml(content: &str) -> Result<Vec<Dependency>> {
+ let pylock: PylockToml =
+ toml::from_str(content).context("Failed to parse pylock.toml format")?;
+
+ let dependencies = pylock
+ .packages
+ .into_iter()
+ .map(|pkg| Dependency {
+ version: pkg.version.unwrap_or_else(|| "unknown".to_string()),
+ name: pkg.name,
+ })
+ .collect();
+
+ Ok(dependencies)
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+
+ #[test]
+ fn test_parse_versioned_packages() {
+ let sample = r#"
+lock-version = "1.0"
+created-by = "uv"
+requires-python = ">=3.12"
+
+[[packages]]
+name = "bottle"
+version = "0.13.4"
+
+[[packages]]
+name = "requests"
+version = "2.31.0"
+"#;
+
+ let deps = parse_pylock_toml(sample).unwrap();
+ assert_eq!(deps.len(), 2);
+ assert_eq!(deps[0].name, "bottle");
+ assert_eq!(deps[0].version, "0.13.4");
+ assert_eq!(deps[1].name, "requests");
+ assert_eq!(deps[1].version, "2.31.0");
+ }
+
+ #[test]
+ fn test_parse_directory_dependency_uses_unknown() {
+ // PEP 751: version MUST NOT be included for source trees.
+ // We record "unknown" so the dependency is still visible.
+ let sample = r#"
+lock-version = "1.0"
+created-by = "uv"
+requires-python = ">=3.12"
+
+[[packages]]
+name = "bottle"
+version = "0.13.4"
+
+[[packages]]
+name = "fastly-compute"
+directory = { path = "../../", editable = true }
+"#;
+
+ let deps = parse_pylock_toml(sample).unwrap();
+ assert_eq!(deps.len(), 2);
+ assert_eq!(deps[1].name, "fastly-compute");
+ assert_eq!(deps[1].version, "unknown");
+ }
+}

crates/fastly-compute-py/src/lib.rs

@@ -14,6 +14,7 @@ use wasm_metadata::AddMetadata;
 
 pub mod cli;
 pub mod config;
+pub mod dependencies;
 pub mod site_packages;
 
 use cli::Cli;
@@ -113,6 +114,34 @@ pub fn run_main(cli: &Cli) -> Result<()> {
  output_dir,
  )?;
  }
+ cli::Command::Dependencies {
+ format,
+ output,
+ virtualenv,
+ } => {
+ let deps = dependencies::get_dependencies(virtualenv)?;
+
+ match format {
+ cli::DependencyFormat::Json => {
+ // Convert to HashMap matching fastly_data packages format
+ let mut packages = std::collections::HashMap::new();
+ for dep in deps {
+ packages.insert(dep.name, dep.version);
+ }
+
+ let json = serde_json::to_string_pretty(&packages)
+ .context("Failed to serialize dependencies to JSON")?;
+
+ match output {
+ Some(path) => {
+ fs::write(path, &json)
+ .context("Failed to write dependencies to output file")?;
+ }
+ None => println!("{}", json),
+ }
+ }
+ }
+ }
  }
 
  Ok(())
@@ -223,7 +252,7 @@ pub fn build(output: PathBuf, entry_name: String, virtualenv: Option<PathBuf>) -
  compose_with_wasiless(&temp_component_wasm_path, WASILESS_WASM, WRAP_WAC, &output)?;
 
  log::info!(" Injecting Fastly metadata...");
- let annotated = inject_fastly_metadata(composed)?;
+ let annotated = inject_fastly_metadata(composed, &virtualenv)?;
 
  fs::write(&output, annotated)
  .with_context(|| format!("Failed to write output: {}", output.display()))?;
@@ -302,16 +331,18 @@ fn compose_with_wasiless(
 /// - `processed-by: componentize-py <version>` — the tool that performed the
 /// core Wasm transformation. `fastly-compute-py` also adds itself here as
 /// the build orchestrator.
+/// - `processed-by: fastly_data` — package dependency list in the same JSON
+/// format the Fastly CLI uses for all other languages. The CLI merges its
+/// own fields (build_info, machine_info, script_info) on top and skips
+/// re-collecting package_info when this key is already present.
 ///
 /// Note: the Fastly-proprietary `fastly.manifest.*` custom sections
 /// (language, version, service_id, etc.) are **not** written here. Those are
 /// injected during package ingestion, sourced from the `fastly.toml` manifest
 /// that the CLI bundles alongside the Wasm in the upload package.
-/// Dependency lists, build scripts, and machine info are similarly the CLI's
-/// responsibility via its `fastly_data` producers entry.
 ///
 /// [Producers Section spec]: https://github.com/WebAssembly/tool-conventions/blob/main/ProducersSection.md
-fn inject_fastly_metadata(wasm: Vec<u8>) -> Result<Vec<u8>> {
+fn inject_fastly_metadata(wasm: Vec<u8>, virtualenv: &Option<PathBuf>) -> Result<Vec<u8>> {
  let mut add_metadata = AddMetadata::default();
 
  // Source language. The version is the CPython version bundled by
@@ -337,6 +368,19 @@ fn inject_fastly_metadata(wasm: Vec<u8>) -> Result<Vec<u8>> {
  env!("CARGO_PKG_VERSION").to_owned(),
  ));
 
+ // Inject dependencies as fastly_data, matching the format the Fastly CLI
+ // writes for other languages. The CLI merges its own fields on top and
+ // skips re-collecting package_info when this key is already present.
+ let fastly_data_json = dependencies::get_fastly_data_json(virtualenv)?;
+ if !fastly_data_json.is_empty() {
+ log::debug!("Injecting fastly_data with package dependencies");
+ add_metadata
+ .processed_by
+ .push(("fastly_data".to_owned(), fastly_data_json));
+ } else {
+ log::debug!("No dependencies found to inject");
+ }
+
  add_metadata
  .to_wasm(&wasm)
  .context("Failed to add producers metadata to Wasm component")

fastly_compute/runtime_patching/patches.py

@@ -40,7 +40,8 @@
  # the wit_world, is around.
  def patch():
  """Pretend to patch."""
- print("Faking the run of exception-mapping monkeypatches for test runner.")
+ import sys
+ print("Faking the run of exception-mapping monkeypatches for test runner.", file=sys.stderr)
 else:
  MAPPINGS = {
  wit_world.imports.acl.AclError.GENERIC_ERROR: fastly_compute.exceptions.acl.acl_error.GenericError,

Makefile

@@ -73,11 +73,11 @@ serve: $(WASM_FILE)
 
 # Test all examples (requires all WASM files to be built)
 test: $(COMPOSED_WASMS)
-	VICEROY=$(VICEROY) uv run --extra test pytest
+	VICEROY=$(VICEROY) FASTLY_COMPUTE_PY="$(FASTLY_COMPUTE_PY)" uv run --extra test pytest
 
 # Update snapshots for snapshot tests
 test-update-snapshots: $(COMPOSED_WASMS)
-	VICEROY=$(VICEROY) uv run --extra test pytest --snapshot-update
+	VICEROY=$(VICEROY) FASTLY_COMPUTE_PY="$(FASTLY_COMPUTE_PY)" uv run --extra test pytest --snapshot-update
 
 # List available examples
 list-examples:

crates/fastly-compute-py/Cargo.toml

@@ -29,6 +29,7 @@ componentize-py = { git = "https://github.com/bytecodealliance/componentize-py",
 futures = { version = "0.3", default-features = false, features = ["executor"] }
 pyo3 = { version = "0.28.3", features = ["abi3-py312"], optional = true }
 serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
 toml = "0.8"
 log = "0.4"
 env_logger = "0.11"

crates/fastly-compute-py/build.rs

@@ -12,7 +12,8 @@ fn main() -> Result<()> {
  println!("cargo:rerun-if-changed=../../wrap_app_in_wasiless.wac");
  println!("cargo:rerun-if-changed=../../Cargo.lock");
 
- let root_dir = PathBuf::from("../../");
+ let manifest_dir = env::var("CARGO_MANIFEST_DIR").expect("Failed to get CARGO_MANIFEST_DIR");
+ let root_dir: PathBuf = [&manifest_dir, "..", ".."].iter().collect();
  let wit_dir = root_dir.join("wit");
  let out_dir = PathBuf::from(env::var("OUT_DIR")?);
 

crates/fastly-compute-py/src/cli.rs

@@ -36,7 +36,6 @@ pub enum Command {
  #[arg(short, long)]
  virtualenv: Option<PathBuf>,
  },
-
  /// Generate WIT binding stubs for use with type checkers and IDEs
  Bindings {
  /// WIT directory to generate bindings from (default: wit)
@@ -54,4 +53,26 @@ pub enum Command {
  /// Output directory for the generated stubs
  output_dir: PathBuf,
  },
+ /// List project dependencies in the specified format
+ Dependencies {
+ /// Output format for dependencies
+ #[arg(short, long, default_value = "json")]
+ format: DependencyFormat,
+
+ /// Write output to this file instead of stdout
+ #[arg(short, long)]
+ output: Option<PathBuf>,
+
+ /// Virtual environment in which to look for modules (default:
+ /// VIRTUAL_ENV env var or .venv)
+ #[arg(short, long)]
+ virtualenv: Option<PathBuf>,
+ },
+}
+
+#[derive(Clone, Debug, clap::ValueEnum)]
+pub enum DependencyFormat {
+ /// JSON object format: {"package-name": "1.0.0", ...}
+ /// Matches the format used in fastly_data metadata
+ Json,
 }

crates/fastly-compute-py/src/config.rs

@@ -75,6 +75,7 @@ impl ConfigBuilder {
  self.cli.virtualenv = virtualenv.clone();
  }
  Command::Bindings { .. } => {}
+ Command::Dependencies { .. } => {}
  }
  self
  }

crates/fastly-compute-py/src/dependencies.rs

@@ -0,0 +1,198 @@
+use anyhow::{Context, Result};
+use serde::{Deserialize, Serialize};
+use std::collections::HashMap;
+use std::path::PathBuf;
+use std::process::Command;
+
+/// A single package dependency with name and version
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct Dependency {
+ pub name: String,
+ pub version: String,
+}
+
+/// Fastly CLI DataCollection format for fastly_data metadata.
+/// Matches the Go structs in pkg/commands/compute/build.go.
+#[derive(Debug, Serialize)]
+pub struct FastlyData {
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub package_info: Option<PackageInfo>,
+}
+
+#[derive(Debug, Serialize)]
+pub struct PackageInfo {
+ pub packages: HashMap<String, String>,
+}
+
+/// PEP 751 pylock.toml format structures
+#[derive(Debug, Deserialize)]
+struct PylockToml {
+ #[serde(rename = "lock-version")]
+ _lock_version: String,
+ packages: Vec<PylockPackage>,
+}
+
+#[derive(Debug, Deserialize)]
+struct PylockPackage {
+ name: String,
+ /// Present for registry/VCS packages; absent for local source trees
+ /// (PEP 751: version MUST NOT be included when using a source tree)
+ version: Option<String>,
+}
+
+/// Get dependencies using UV's PEP 751 export.
+///
+/// Dependency collection only runs when both conditions are met:
+///
+/// 1. A `pyproject.toml` exists in the current directory — confirming this is
+/// a Python project that could have a lockfile. Without this, `uv export`
+/// would fail with "no pyproject.toml found" (e.g. the Viceroy test
+/// framework builds in a temp dir with no project files).
+///
+/// 2. The `UV` environment variable is set — confirming the tool was invoked
+/// via `uv run` or similar. We don't guess that `uv` should be used just
+/// because a `uv` binary happens to be on PATH; the user may be using pip,
+/// poetry, or another tool entirely.
+///
+/// When both conditions are met, errors from `uv export` are bubbled up since
+/// something genuinely went wrong in a context where UV is expected to work.
+pub fn get_dependencies(_virtualenv: &Option<PathBuf>) -> Result<Vec<Dependency>> {
+ if !std::fs::exists("pyproject.toml").unwrap_or_default() {
+ log::debug!("No pyproject.toml found, skipping dependency collection");
+ return Ok(Vec::new());
+ }
+
+ let uv_bin = match std::env::var("UV") {
+ Ok(bin) => bin,
+ Err(_) => {
+ log::debug!("UV env var not set, skipping dependency collection");
+ return Ok(Vec::new());
+ }
+ };
+
+ log::info!("Collecting dependencies from project environment...");
+
+ let deps = get_dependencies_from_uv(&uv_bin)?;
+ log::info!("Found {} dependencies via UV", deps.len());
+ Ok(deps)
+}
+
+/// Serialize dependencies as fastly_data JSON, matching the CLI's DataCollection format.
+///
+/// The build tool injects this directly so the CLI does not need to know anything
+/// about the Python environment to collect package metadata.
+pub fn get_fastly_data_json(virtualenv: &Option<PathBuf>) -> Result<String> {
+ let deps = get_dependencies(virtualenv)?;
+
+ if deps.is_empty() {
+ return Ok(String::new());
+ }
+
+ let packages: HashMap<String, String> = deps.into_iter().map(|d| (d.name, d.version)).collect();
+
+ let fastly_data = FastlyData {
+ package_info: Some(PackageInfo { packages }),
+ };
+
+ serde_json::to_string(&fastly_data).context("Failed to serialize fastly_data to JSON")
+}
+
+/// Use UV export to get dependencies in PEP 751 pylock.toml format
+fn get_dependencies_from_uv(uv_bin: &str) -> Result<Vec<Dependency>> {
+ log::debug!(
+ "Attempting to export dependencies using UV binary: {}",
+ uv_bin
+ );
+
+ let output = Command::new(uv_bin)
+ .args([
+ "export",
+ "--format",
+ "pylock.toml",
+ "--no-emit-project",
+ "--frozen",
+ "--no-header",
+ ])
+ .output()
+ .context("Failed to run 'uv export'")?;
+
+ if !output.status.success() {
+ let stderr = String::from_utf8_lossy(&output.stderr);
+ anyhow::bail!("uv export failed: {}", stderr);
+ }
+
+ let pylock_content =
+ String::from_utf8(output.stdout).context("UV output was not valid UTF-8")?;
+
+ parse_pylock_toml(&pylock_content)
+}
+
+/// Parse PEP 751 pylock.toml format
+fn parse_pylock_toml(content: &str) -> Result<Vec<Dependency>> {
+ let pylock: PylockToml =
+ toml::from_str(content).context("Failed to parse pylock.toml format")?;
+
+ let dependencies = pylock
+ .packages
+ .into_iter()
+ .map(|pkg| Dependency {
+ version: pkg.version.unwrap_or_else(|| "unknown".to_string()),
+ name: pkg.name,
+ })
+ .collect();
+
+ Ok(dependencies)
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+
+ #[test]
+ fn test_parse_versioned_packages() {
+ let sample = r#"
+lock-version = "1.0"
+created-by = "uv"
+requires-python = ">=3.12"
+
+[[packages]]
+name = "bottle"
+version = "0.13.4"
+
+[[packages]]
+name = "requests"
+version = "2.31.0"
+"#;
+
+ let deps = parse_pylock_toml(sample).unwrap();
+ assert_eq!(deps.len(), 2);
+ assert_eq!(deps[0].name, "bottle");
+ assert_eq!(deps[0].version, "0.13.4");
+ assert_eq!(deps[1].name, "requests");
+ assert_eq!(deps[1].version, "2.31.0");
+ }
+
+ #[test]
+ fn test_parse_directory_dependency_uses_unknown() {
+ // PEP 751: version MUST NOT be included for source trees.
+ // We record "unknown" so the dependency is still visible.
+ let sample = r#"
+lock-version = "1.0"
+created-by = "uv"
+requires-python = ">=3.12"
+
+[[packages]]
+name = "bottle"
+version = "0.13.4"
+
+[[packages]]
+name = "fastly-compute"
+directory = { path = "../../", editable = true }
+"#;
+
+ let deps = parse_pylock_toml(sample).unwrap();
+ assert_eq!(deps.len(), 2);
+ assert_eq!(deps[1].name, "fastly-compute");
+ assert_eq!(deps[1].version, "unknown");
+ }
+}

crates/fastly-compute-py/src/lib.rs

@@ -14,6 +14,7 @@ use wasm_metadata::AddMetadata;
 
 pub mod cli;
 pub mod config;
+pub mod dependencies;
 pub mod site_packages;
 
 use cli::Cli;
@@ -113,6 +114,34 @@ pub fn run_main(cli: &Cli) -> Result<()> {
  output_dir,
  )?;
  }
+ cli::Command::Dependencies {
+ format,
+ output,
+ virtualenv,
+ } => {
+ let deps = dependencies::get_dependencies(virtualenv)?;
+
+ match format {
+ cli::DependencyFormat::Json => {
+ // Convert to HashMap matching fastly_data packages format
+ let mut packages = std::collections::HashMap::new();
+ for dep in deps {
+ packages.insert(dep.name, dep.version);
+ }
+
+ let json = serde_json::to_string_pretty(&packages)
+ .context("Failed to serialize dependencies to JSON")?;
+
+ match output {
+ Some(path) => {
+ fs::write(path, &json)
+ .context("Failed to write dependencies to output file")?;
+ }
+ None => println!("{}", json),
+ }
+ }
+ }
+ }
  }
 
  Ok(())
@@ -223,7 +252,7 @@ pub fn build(output: PathBuf, entry_name: String, virtualenv: Option<PathBuf>) -
  compose_with_wasiless(&temp_component_wasm_path, WASILESS_WASM, WRAP_WAC, &output)?;
 
  log::info!(" Injecting Fastly metadata...");
- let annotated = inject_fastly_metadata(composed)?;
+ let annotated = inject_fastly_metadata(composed, &virtualenv)?;
 
  fs::write(&output, annotated)
  .with_context(|| format!("Failed to write output: {}", output.display()))?;
@@ -302,16 +331,18 @@ fn compose_with_wasiless(
 /// - `processed-by: componentize-py <version>` — the tool that performed the
 /// core Wasm transformation. `fastly-compute-py` also adds itself here as
 /// the build orchestrator.
+/// - `processed-by: fastly_data` — package dependency list in the same JSON
+/// format the Fastly CLI uses for all other languages. The CLI merges its
+/// own fields (build_info, machine_info, script_info) on top and skips
+/// re-collecting package_info when this key is already present.
 ///
 /// Note: the Fastly-proprietary `fastly.manifest.*` custom sections
 /// (language, version, service_id, etc.) are **not** written here. Those are
 /// injected during package ingestion, sourced from the `fastly.toml` manifest
 /// that the CLI bundles alongside the Wasm in the upload package.
-/// Dependency lists, build scripts, and machine info are similarly the CLI's
-/// responsibility via its `fastly_data` producers entry.
 ///
 /// [Producers Section spec]: https://github.com/WebAssembly/tool-conventions/blob/main/ProducersSection.md
-fn inject_fastly_metadata(wasm: Vec<u8>) -> Result<Vec<u8>> {
+fn inject_fastly_metadata(wasm: Vec<u8>, virtualenv: &Option<PathBuf>) -> Result<Vec<u8>> {
  let mut add_metadata = AddMetadata::default();
 
  // Source language. The version is the CPython version bundled by
@@ -337,6 +368,19 @@ fn inject_fastly_metadata(wasm: Vec<u8>) -> Result<Vec<u8>> {
  env!("CARGO_PKG_VERSION").to_owned(),
  ));
 
+ // Inject dependencies as fastly_data, matching the format the Fastly CLI
+ // writes for other languages. The CLI merges its own fields on top and
+ // skips re-collecting package_info when this key is already present.
+ let fastly_data_json = dependencies::get_fastly_data_json(virtualenv)?;
+ if !fastly_data_json.is_empty() {
+ log::debug!("Injecting fastly_data with package dependencies");
+ add_metadata
+ .processed_by
+ .push(("fastly_data".to_owned(), fastly_data_json));
+ } else {
+ log::debug!("No dependencies found to inject");
+ }
+
  add_metadata
  .to_wasm(&wasm)
  .context("Failed to add producers metadata to Wasm component")

fastly_compute/runtime_patching/patches.py

@@ -40,7 +40,8 @@
  # the wit_world, is around.
  def patch():
  """Pretend to patch."""
- print("Faking the run of exception-mapping monkeypatches for test runner.")
+ import sys
+ print("Faking the run of exception-mapping monkeypatches for test runner.", file=sys.stderr)
 else:
  MAPPINGS = {
  wit_world.imports.acl.AclError.GENERIC_ERROR: fastly_compute.exceptions.acl.acl_error.GenericError,

Makefile

@@ -73,11 +73,11 @@ serve: $(WASM_FILE)
 
 # Test all examples (requires all WASM files to be built)
 test: $(COMPOSED_WASMS)
-	VICEROY=$(VICEROY) uv run --extra test pytest
+	VICEROY=$(VICEROY) FASTLY_COMPUTE_PY="$(FASTLY_COMPUTE_PY)" uv run --extra test pytest
 
 # Update snapshots for snapshot tests
 test-update-snapshots: $(COMPOSED_WASMS)
-	VICEROY=$(VICEROY) uv run --extra test pytest --snapshot-update
+	VICEROY=$(VICEROY) FASTLY_COMPUTE_PY="$(FASTLY_COMPUTE_PY)" uv run --extra test pytest --snapshot-update
 
 # List available examples
 list-examples:

crates/fastly-compute-py/Cargo.toml

@@ -29,6 +29,7 @@ componentize-py = { git = "https://github.com/bytecodealliance/componentize-py",
 futures = { version = "0.3", default-features = false, features = ["executor"] }
 pyo3 = { version = "0.28.3", features = ["abi3-py312"], optional = true }
 serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
 toml = "0.8"
 log = "0.4"
 env_logger = "0.11"

crates/fastly-compute-py/build.rs

@@ -12,7 +12,8 @@ fn main() -> Result<()> {
  println!("cargo:rerun-if-changed=../../wrap_app_in_wasiless.wac");
  println!("cargo:rerun-if-changed=../../Cargo.lock");
 
- let root_dir = PathBuf::from("../../");
+ let manifest_dir = env::var("CARGO_MANIFEST_DIR").expect("Failed to get CARGO_MANIFEST_DIR");
+ let root_dir: PathBuf = [&manifest_dir, "..", ".."].iter().collect();
  let wit_dir = root_dir.join("wit");
  let out_dir = PathBuf::from(env::var("OUT_DIR")?);
 

crates/fastly-compute-py/src/cli.rs

@@ -36,7 +36,6 @@ pub enum Command {
  #[arg(short, long)]
  virtualenv: Option<PathBuf>,
  },
-
  /// Generate WIT binding stubs for use with type checkers and IDEs
  Bindings {
  /// WIT directory to generate bindings from (default: wit)
@@ -54,4 +53,26 @@ pub enum Command {
  /// Output directory for the generated stubs
  output_dir: PathBuf,
  },
+ /// List project dependencies in the specified format
+ Dependencies {
+ /// Output format for dependencies
+ #[arg(short, long, default_value = "json")]
+ format: DependencyFormat,
+
+ /// Write output to this file instead of stdout
+ #[arg(short, long)]
+ output: Option<PathBuf>,
+
+ /// Virtual environment in which to look for modules (default:
+ /// VIRTUAL_ENV env var or .venv)
+ #[arg(short, long)]
+ virtualenv: Option<PathBuf>,
+ },
+}
+
+#[derive(Clone, Debug, clap::ValueEnum)]
+pub enum DependencyFormat {
+ /// JSON object format: {"package-name": "1.0.0", ...}
+ /// Matches the format used in fastly_data metadata
+ Json,
 }

crates/fastly-compute-py/src/config.rs

@@ -75,6 +75,7 @@ impl ConfigBuilder {
  self.cli.virtualenv = virtualenv.clone();
  }
  Command::Bindings { .. } => {}
+ Command::Dependencies { .. } => {}
  }
  self
  }

crates/fastly-compute-py/src/dependencies.rs

@@ -0,0 +1,198 @@
+use anyhow::{Context, Result};
+use serde::{Deserialize, Serialize};
+use std::collections::HashMap;
+use std::path::PathBuf;
+use std::process::Command;
+
+/// A single package dependency with name and version
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct Dependency {
+ pub name: String,
+ pub version: String,
+}
+
+/// Fastly CLI DataCollection format for fastly_data metadata.
+/// Matches the Go structs in pkg/commands/compute/build.go.
+#[derive(Debug, Serialize)]
+pub struct FastlyData {
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub package_info: Option<PackageInfo>,
+}
+
+#[derive(Debug, Serialize)]
+pub struct PackageInfo {
+ pub packages: HashMap<String, String>,
+}
+
+/// PEP 751 pylock.toml format structures
+#[derive(Debug, Deserialize)]
+struct PylockToml {
+ #[serde(rename = "lock-version")]
+ _lock_version: String,
+ packages: Vec<PylockPackage>,
+}
+
+#[derive(Debug, Deserialize)]
+struct PylockPackage {
+ name: String,
+ /// Present for registry/VCS packages; absent for local source trees
+ /// (PEP 751: version MUST NOT be included when using a source tree)
+ version: Option<String>,
+}
+
+/// Get dependencies using UV's PEP 751 export.
+///
+/// Dependency collection only runs when both conditions are met:
+///
+/// 1. A `pyproject.toml` exists in the current directory — confirming this is
+/// a Python project that could have a lockfile. Without this, `uv export`
+/// would fail with "no pyproject.toml found" (e.g. the Viceroy test
+/// framework builds in a temp dir with no project files).
+///
+/// 2. The `UV` environment variable is set — confirming the tool was invoked
+/// via `uv run` or similar. We don't guess that `uv` should be used just
+/// because a `uv` binary happens to be on PATH; the user may be using pip,
+/// poetry, or another tool entirely.
+///
+/// When both conditions are met, errors from `uv export` are bubbled up since
+/// something genuinely went wrong in a context where UV is expected to work.
+pub fn get_dependencies(_virtualenv: &Option<PathBuf>) -> Result<Vec<Dependency>> {
+ if !std::fs::exists("pyproject.toml").unwrap_or_default() {
+ log::debug!("No pyproject.toml found, skipping dependency collection");
+ return Ok(Vec::new());
+ }
+
+ let uv_bin = match std::env::var("UV") {
+ Ok(bin) => bin,
+ Err(_) => {
+ log::debug!("UV env var not set, skipping dependency collection");
+ return Ok(Vec::new());
+ }
+ };
+
+ log::info!("Collecting dependencies from project environment...");
+
+ let deps = get_dependencies_from_uv(&uv_bin)?;
+ log::info!("Found {} dependencies via UV", deps.len());
+ Ok(deps)
+}
+
+/// Serialize dependencies as fastly_data JSON, matching the CLI's DataCollection format.
+///
+/// The build tool injects this directly so the CLI does not need to know anything
+/// about the Python environment to collect package metadata.
+pub fn get_fastly_data_json(virtualenv: &Option<PathBuf>) -> Result<String> {
+ let deps = get_dependencies(virtualenv)?;
+
+ if deps.is_empty() {
+ return Ok(String::new());
+ }
+
+ let packages: HashMap<String, String> = deps.into_iter().map(|d| (d.name, d.version)).collect();
+
+ let fastly_data = FastlyData {
+ package_info: Some(PackageInfo { packages }),
+ };
+
+ serde_json::to_string(&fastly_data).context("Failed to serialize fastly_data to JSON")
+}
+
+/// Use UV export to get dependencies in PEP 751 pylock.toml format
+fn get_dependencies_from_uv(uv_bin: &str) -> Result<Vec<Dependency>> {
+ log::debug!(
+ "Attempting to export dependencies using UV binary: {}",
+ uv_bin
+ );
+
+ let output = Command::new(uv_bin)
+ .args([
+ "export",
+ "--format",
+ "pylock.toml",
+ "--no-emit-project",
+ "--frozen",
+ "--no-header",
+ ])
+ .output()
+ .context("Failed to run 'uv export'")?;
+
+ if !output.status.success() {
+ let stderr = String::from_utf8_lossy(&output.stderr);
+ anyhow::bail!("uv export failed: {}", stderr);
+ }
+
+ let pylock_content =
+ String::from_utf8(output.stdout).context("UV output was not valid UTF-8")?;
+
+ parse_pylock_toml(&pylock_content)
+}
+
+/// Parse PEP 751 pylock.toml format
+fn parse_pylock_toml(content: &str) -> Result<Vec<Dependency>> {
+ let pylock: PylockToml =
+ toml::from_str(content).context("Failed to parse pylock.toml format")?;
+
+ let dependencies = pylock
+ .packages
+ .into_iter()
+ .map(|pkg| Dependency {
+ version: pkg.version.unwrap_or_else(|| "unknown".to_string()),
+ name: pkg.name,
+ })
+ .collect();
+
+ Ok(dependencies)
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+
+ #[test]
+ fn test_parse_versioned_packages() {
+ let sample = r#"
+lock-version = "1.0"
+created-by = "uv"
+requires-python = ">=3.12"
+
+[[packages]]
+name = "bottle"
+version = "0.13.4"
+
+[[packages]]
+name = "requests"
+version = "2.31.0"
+"#;
+
+ let deps = parse_pylock_toml(sample).unwrap();
+ assert_eq!(deps.len(), 2);
+ assert_eq!(deps[0].name, "bottle");
+ assert_eq!(deps[0].version, "0.13.4");
+ assert_eq!(deps[1].name, "requests");
+ assert_eq!(deps[1].version, "2.31.0");
+ }
+
+ #[test]
+ fn test_parse_directory_dependency_uses_unknown() {
+ // PEP 751: version MUST NOT be included for source trees.
+ // We record "unknown" so the dependency is still visible.
+ let sample = r#"
+lock-version = "1.0"
+created-by = "uv"
+requires-python = ">=3.12"
+
+[[packages]]
+name = "bottle"
+version = "0.13.4"
+
+[[packages]]
+name = "fastly-compute"
+directory = { path = "../../", editable = true }
+"#;
+
+ let deps = parse_pylock_toml(sample).unwrap();
+ assert_eq!(deps.len(), 2);
+ assert_eq!(deps[1].name, "fastly-compute");
+ assert_eq!(deps[1].version, "unknown");
+ }
+}

crates/fastly-compute-py/src/lib.rs

@@ -14,6 +14,7 @@ use wasm_metadata::AddMetadata;
 
 pub mod cli;
 pub mod config;
+pub mod dependencies;
 pub mod site_packages;
 
 use cli::Cli;
@@ -113,6 +114,34 @@ pub fn run_main(cli: &Cli) -> Result<()> {
  output_dir,
  )?;
  }
+ cli::Command::Dependencies {
+ format,
+ output,
+ virtualenv,
+ } => {
+ let deps = dependencies::get_dependencies(virtualenv)?;
+
+ match format {
+ cli::DependencyFormat::Json => {
+ // Convert to HashMap matching fastly_data packages format
+ let mut packages = std::collections::HashMap::new();
+ for dep in deps {
+ packages.insert(dep.name, dep.version);
+ }
+
+ let json = serde_json::to_string_pretty(&packages)
+ .context("Failed to serialize dependencies to JSON")?;
+
+ match output {
+ Some(path) => {
+ fs::write(path, &json)
+ .context("Failed to write dependencies to output file")?;
+ }
+ None => println!("{}", json),
+ }
+ }
+ }
+ }
  }
 
  Ok(())
@@ -223,7 +252,7 @@ pub fn build(output: PathBuf, entry_name: String, virtualenv: Option<PathBuf>) -
  compose_with_wasiless(&temp_component_wasm_path, WASILESS_WASM, WRAP_WAC, &output)?;
 
  log::info!(" Injecting Fastly metadata...");
- let annotated = inject_fastly_metadata(composed)?;
+ let annotated = inject_fastly_metadata(composed, &virtualenv)?;
 
  fs::write(&output, annotated)
  .with_context(|| format!("Failed to write output: {}", output.display()))?;
@@ -302,16 +331,18 @@ fn compose_with_wasiless(
 /// - `processed-by: componentize-py <version>` — the tool that performed the
 /// core Wasm transformation. `fastly-compute-py` also adds itself here as
 /// the build orchestrator.
+/// - `processed-by: fastly_data` — package dependency list in the same JSON
+/// format the Fastly CLI uses for all other languages. The CLI merges its
+/// own fields (build_info, machine_info, script_info) on top and skips
+/// re-collecting package_info when this key is already present.
 ///
 /// Note: the Fastly-proprietary `fastly.manifest.*` custom sections
 /// (language, version, service_id, etc.) are **not** written here. Those are
 /// injected during package ingestion, sourced from the `fastly.toml` manifest
 /// that the CLI bundles alongside the Wasm in the upload package.
-/// Dependency lists, build scripts, and machine info are similarly the CLI's
-/// responsibility via its `fastly_data` producers entry.
 ///
 /// [Producers Section spec]: https://github.com/WebAssembly/tool-conventions/blob/main/ProducersSection.md
-fn inject_fastly_metadata(wasm: Vec<u8>) -> Result<Vec<u8>> {
+fn inject_fastly_metadata(wasm: Vec<u8>, virtualenv: &Option<PathBuf>) -> Result<Vec<u8>> {
  let mut add_metadata = AddMetadata::default();
 
  // Source language. The version is the CPython version bundled by
@@ -337,6 +368,19 @@ fn inject_fastly_metadata(wasm: Vec<u8>) -> Result<Vec<u8>> {
  env!("CARGO_PKG_VERSION").to_owned(),
  ));
 
+ // Inject dependencies as fastly_data, matching the format the Fastly CLI
+ // writes for other languages. The CLI merges its own fields on top and
+ // skips re-collecting package_info when this key is already present.
+ let fastly_data_json = dependencies::get_fastly_data_json(virtualenv)?;
+ if !fastly_data_json.is_empty() {
+ log::debug!("Injecting fastly_data with package dependencies");
+ add_metadata
+ .processed_by
+ .push(("fastly_data".to_owned(), fastly_data_json));
+ } else {
+ log::debug!("No dependencies found to inject");
+ }
+
  add_metadata
  .to_wasm(&wasm)
  .context("Failed to add producers metadata to Wasm component")

fastly_compute/runtime_patching/patches.py

@@ -40,7 +40,8 @@
  # the wit_world, is around.
  def patch():
  """Pretend to patch."""
- print("Faking the run of exception-mapping monkeypatches for test runner.")
+ import sys
+ print("Faking the run of exception-mapping monkeypatches for test runner.", file=sys.stderr)
 else:
  MAPPINGS = {
  wit_world.imports.acl.AclError.GENERIC_ERROR: fastly_compute.exceptions.acl.acl_error.GenericError,

Makefile

@@ -73,11 +73,11 @@ serve: $(WASM_FILE)
 
 # Test all examples (requires all WASM files to be built)
 test: $(COMPOSED_WASMS)
-	VICEROY=$(VICEROY) uv run --extra test pytest
+	VICEROY=$(VICEROY) FASTLY_COMPUTE_PY="$(FASTLY_COMPUTE_PY)" uv run --extra test pytest
 
 # Update snapshots for snapshot tests
 test-update-snapshots: $(COMPOSED_WASMS)
-	VICEROY=$(VICEROY) uv run --extra test pytest --snapshot-update
+	VICEROY=$(VICEROY) FASTLY_COMPUTE_PY="$(FASTLY_COMPUTE_PY)" uv run --extra test pytest --snapshot-update
 
 # List available examples
 list-examples:

crates/fastly-compute-py/Cargo.toml

@@ -29,6 +29,7 @@ componentize-py = { git = "https://github.com/bytecodealliance/componentize-py",
 futures = { version = "0.3", default-features = false, features = ["executor"] }
 pyo3 = { version = "0.28.3", features = ["abi3-py312"], optional = true }
 serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
 toml = "0.8"
 log = "0.4"
 env_logger = "0.11"

crates/fastly-compute-py/build.rs

@@ -12,7 +12,8 @@ fn main() -> Result<()> {
  println!("cargo:rerun-if-changed=../../wrap_app_in_wasiless.wac");
  println!("cargo:rerun-if-changed=../../Cargo.lock");
 
- let root_dir = PathBuf::from("../../");
+ let manifest_dir = env::var("CARGO_MANIFEST_DIR").expect("Failed to get CARGO_MANIFEST_DIR");
+ let root_dir: PathBuf = [&manifest_dir, "..", ".."].iter().collect();
  let wit_dir = root_dir.join("wit");
  let out_dir = PathBuf::from(env::var("OUT_DIR")?);
 

crates/fastly-compute-py/src/cli.rs

@@ -36,7 +36,6 @@ pub enum Command {
  #[arg(short, long)]
  virtualenv: Option<PathBuf>,
  },
-
  /// Generate WIT binding stubs for use with type checkers and IDEs
  Bindings {
  /// WIT directory to generate bindings from (default: wit)
@@ -54,4 +53,26 @@ pub enum Command {
  /// Output directory for the generated stubs
  output_dir: PathBuf,
  },
+ /// List project dependencies in the specified format
+ Dependencies {
+ /// Output format for dependencies
+ #[arg(short, long, default_value = "json")]
+ format: DependencyFormat,
+
+ /// Write output to this file instead of stdout
+ #[arg(short, long)]
+ output: Option<PathBuf>,
+
+ /// Virtual environment in which to look for modules (default:
+ /// VIRTUAL_ENV env var or .venv)
+ #[arg(short, long)]
+ virtualenv: Option<PathBuf>,
+ },
+}
+
+#[derive(Clone, Debug, clap::ValueEnum)]
+pub enum DependencyFormat {
+ /// JSON object format: {"package-name": "1.0.0", ...}
+ /// Matches the format used in fastly_data metadata
+ Json,
 }

crates/fastly-compute-py/src/config.rs

@@ -75,6 +75,7 @@ impl ConfigBuilder {
  self.cli.virtualenv = virtualenv.clone();
  }
  Command::Bindings { .. } => {}
+ Command::Dependencies { .. } => {}
  }
  self
  }

crates/fastly-compute-py/src/dependencies.rs

@@ -0,0 +1,198 @@
+use anyhow::{Context, Result};
+use serde::{Deserialize, Serialize};
+use std::collections::HashMap;
+use std::path::PathBuf;
+use std::process::Command;
+
+/// A single package dependency with name and version
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct Dependency {
+ pub name: String,
+ pub version: String,
+}
+
+/// Fastly CLI DataCollection format for fastly_data metadata.
+/// Matches the Go structs in pkg/commands/compute/build.go.
+#[derive(Debug, Serialize)]
+pub struct FastlyData {
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub package_info: Option<PackageInfo>,
+}
+
+#[derive(Debug, Serialize)]
+pub struct PackageInfo {
+ pub packages: HashMap<String, String>,
+}
+
+/// PEP 751 pylock.toml format structures
+#[derive(Debug, Deserialize)]
+struct PylockToml {
+ #[serde(rename = "lock-version")]
+ _lock_version: String,
+ packages: Vec<PylockPackage>,
+}
+
+#[derive(Debug, Deserialize)]
+struct PylockPackage {
+ name: String,
+ /// Present for registry/VCS packages; absent for local source trees
+ /// (PEP 751: version MUST NOT be included when using a source tree)
+ version: Option<String>,
+}
+
+/// Get dependencies using UV's PEP 751 export.
+///
+/// Dependency collection only runs when both conditions are met:
+///
+/// 1. A `pyproject.toml` exists in the current directory — confirming this is
+/// a Python project that could have a lockfile. Without this, `uv export`
+/// would fail with "no pyproject.toml found" (e.g. the Viceroy test
+/// framework builds in a temp dir with no project files).
+///
+/// 2. The `UV` environment variable is set — confirming the tool was invoked
+/// via `uv run` or similar. We don't guess that `uv` should be used just
+/// because a `uv` binary happens to be on PATH; the user may be using pip,
+/// poetry, or another tool entirely.
+///
+/// When both conditions are met, errors from `uv export` are bubbled up since
+/// something genuinely went wrong in a context where UV is expected to work.
+pub fn get_dependencies(_virtualenv: &Option<PathBuf>) -> Result<Vec<Dependency>> {
+ if !std::fs::exists("pyproject.toml").unwrap_or_default() {
+ log::debug!("No pyproject.toml found, skipping dependency collection");
+ return Ok(Vec::new());
+ }
+
+ let uv_bin = match std::env::var("UV") {
+ Ok(bin) => bin,
+ Err(_) => {
+ log::debug!("UV env var not set, skipping dependency collection");
+ return Ok(Vec::new());
+ }
+ };
+
+ log::info!("Collecting dependencies from project environment...");
+
+ let deps = get_dependencies_from_uv(&uv_bin)?;
+ log::info!("Found {} dependencies via UV", deps.len());
+ Ok(deps)
+}
+
+/// Serialize dependencies as fastly_data JSON, matching the CLI's DataCollection format.
+///
+/// The build tool injects this directly so the CLI does not need to know anything
+/// about the Python environment to collect package metadata.
+pub fn get_fastly_data_json(virtualenv: &Option<PathBuf>) -> Result<String> {
+ let deps = get_dependencies(virtualenv)?;
+
+ if deps.is_empty() {
+ return Ok(String::new());
+ }
+
+ let packages: HashMap<String, String> = deps.into_iter().map(|d| (d.name, d.version)).collect();
+
+ let fastly_data = FastlyData {
+ package_info: Some(PackageInfo { packages }),
+ };
+
+ serde_json::to_string(&fastly_data).context("Failed to serialize fastly_data to JSON")
+}
+
+/// Use UV export to get dependencies in PEP 751 pylock.toml format
+fn get_dependencies_from_uv(uv_bin: &str) -> Result<Vec<Dependency>> {
+ log::debug!(
+ "Attempting to export dependencies using UV binary: {}",
+ uv_bin
+ );
+
+ let output = Command::new(uv_bin)
+ .args([
+ "export",
+ "--format",
+ "pylock.toml",
+ "--no-emit-project",
+ "--frozen",
+ "--no-header",
+ ])
+ .output()
+ .context("Failed to run 'uv export'")?;
+
+ if !output.status.success() {
+ let stderr = String::from_utf8_lossy(&output.stderr);
+ anyhow::bail!("uv export failed: {}", stderr);
+ }
+
+ let pylock_content =
+ String::from_utf8(output.stdout).context("UV output was not valid UTF-8")?;
+
+ parse_pylock_toml(&pylock_content)
+}
+
+/// Parse PEP 751 pylock.toml format
+fn parse_pylock_toml(content: &str) -> Result<Vec<Dependency>> {
+ let pylock: PylockToml =
+ toml::from_str(content).context("Failed to parse pylock.toml format")?;
+
+ let dependencies = pylock
+ .packages
+ .into_iter()
+ .map(|pkg| Dependency {
+ version: pkg.version.unwrap_or_else(|| "unknown".to_string()),
+ name: pkg.name,
+ })
+ .collect();
+
+ Ok(dependencies)
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+
+ #[test]
+ fn test_parse_versioned_packages() {
+ let sample = r#"
+lock-version = "1.0"
+created-by = "uv"
+requires-python = ">=3.12"
+
+[[packages]]
+name = "bottle"
+version = "0.13.4"
+
+[[packages]]
+name = "requests"
+version = "2.31.0"
+"#;
+
+ let deps = parse_pylock_toml(sample).unwrap();
+ assert_eq!(deps.len(), 2);
+ assert_eq!(deps[0].name, "bottle");
+ assert_eq!(deps[0].version, "0.13.4");
+ assert_eq!(deps[1].name, "requests");
+ assert_eq!(deps[1].version, "2.31.0");
+ }
+
+ #[test]
+ fn test_parse_directory_dependency_uses_unknown() {
+ // PEP 751: version MUST NOT be included for source trees.
+ // We record "unknown" so the dependency is still visible.
+ let sample = r#"
+lock-version = "1.0"
+created-by = "uv"
+requires-python = ">=3.12"
+
+[[packages]]
+name = "bottle"
+version = "0.13.4"
+
+[[packages]]
+name = "fastly-compute"
+directory = { path = "../../", editable = true }
+"#;
+
+ let deps = parse_pylock_toml(sample).unwrap();
+ assert_eq!(deps.len(), 2);
+ assert_eq!(deps[1].name, "fastly-compute");
+ assert_eq!(deps[1].version, "unknown");
+ }
+}

crates/fastly-compute-py/src/lib.rs

@@ -14,6 +14,7 @@ use wasm_metadata::AddMetadata;
 
 pub mod cli;
 pub mod config;
+pub mod dependencies;
 pub mod site_packages;
 
 use cli::Cli;
@@ -113,6 +114,34 @@ pub fn run_main(cli: &Cli) -> Result<()> {
  output_dir,
  )?;
  }
+ cli::Command::Dependencies {
+ format,
+ output,
+ virtualenv,
+ } => {
+ let deps = dependencies::get_dependencies(virtualenv)?;
+
+ match format {
+ cli::DependencyFormat::Json => {
+ // Convert to HashMap matching fastly_data packages format
+ let mut packages = std::collections::HashMap::new();
+ for dep in deps {
+ packages.insert(dep.name, dep.version);
+ }
+
+ let json = serde_json::to_string_pretty(&packages)
+ .context("Failed to serialize dependencies to JSON")?;
+
+ match output {
+ Some(path) => {
+ fs::write(path, &json)
+ .context("Failed to write dependencies to output file")?;
+ }
+ None => println!("{}", json),
+ }
+ }
+ }
+ }
  }
 
  Ok(())
@@ -223,7 +252,7 @@ pub fn build(output: PathBuf, entry_name: String, virtualenv: Option<PathBuf>) -
  compose_with_wasiless(&temp_component_wasm_path, WASILESS_WASM, WRAP_WAC, &output)?;
 
  log::info!(" Injecting Fastly metadata...");
- let annotated = inject_fastly_metadata(composed)?;
+ let annotated = inject_fastly_metadata(composed, &virtualenv)?;
 
  fs::write(&output, annotated)
  .with_context(|| format!("Failed to write output: {}", output.display()))?;
@@ -302,16 +331,18 @@ fn compose_with_wasiless(
 /// - `processed-by: componentize-py <version>` — the tool that performed the
 /// core Wasm transformation. `fastly-compute-py` also adds itself here as
 /// the build orchestrator.
+/// - `processed-by: fastly_data` — package dependency list in the same JSON
+/// format the Fastly CLI uses for all other languages. The CLI merges its
+/// own fields (build_info, machine_info, script_info) on top and skips
+/// re-collecting package_info when this key is already present.
 ///
 /// Note: the Fastly-proprietary `fastly.manifest.*` custom sections
 /// (language, version, service_id, etc.) are **not** written here. Those are
 /// injected during package ingestion, sourced from the `fastly.toml` manifest
 /// that the CLI bundles alongside the Wasm in the upload package.
-/// Dependency lists, build scripts, and machine info are similarly the CLI's
-/// responsibility via its `fastly_data` producers entry.
 ///
 /// [Producers Section spec]: https://github.com/WebAssembly/tool-conventions/blob/main/ProducersSection.md
-fn inject_fastly_metadata(wasm: Vec<u8>) -> Result<Vec<u8>> {
+fn inject_fastly_metadata(wasm: Vec<u8>, virtualenv: &Option<PathBuf>) -> Result<Vec<u8>> {
  let mut add_metadata = AddMetadata::default();
 
  // Source language. The version is the CPython version bundled by
@@ -337,6 +368,19 @@ fn inject_fastly_metadata(wasm: Vec<u8>) -> Result<Vec<u8>> {
  env!("CARGO_PKG_VERSION").to_owned(),
  ));
 
+ // Inject dependencies as fastly_data, matching the format the Fastly CLI
+ // writes for other languages. The CLI merges its own fields on top and
+ // skips re-collecting package_info when this key is already present.
+ let fastly_data_json = dependencies::get_fastly_data_json(virtualenv)?;
+ if !fastly_data_json.is_empty() {
+ log::debug!("Injecting fastly_data with package dependencies");
+ add_metadata
+ .processed_by
+ .push(("fastly_data".to_owned(), fastly_data_json));
+ } else {
+ log::debug!("No dependencies found to inject");
+ }
+
  add_metadata
  .to_wasm(&wasm)
  .context("Failed to add producers metadata to Wasm component")

fastly_compute/runtime_patching/patches.py

@@ -40,7 +40,8 @@
  # the wit_world, is around.
  def patch():
  """Pretend to patch."""
- print("Faking the run of exception-mapping monkeypatches for test runner.")
+ import sys
+ print("Faking the run of exception-mapping monkeypatches for test runner.", file=sys.stderr)
 else:
  MAPPINGS = {
  wit_world.imports.acl.AclError.GENERIC_ERROR: fastly_compute.exceptions.acl.acl_error.GenericError,

Makefile

@@ -73,11 +73,11 @@ serve: $(WASM_FILE)
 
 # Test all examples (requires all WASM files to be built)
 test: $(COMPOSED_WASMS)
-	VICEROY=$(VICEROY) uv run --extra test pytest
+	VICEROY=$(VICEROY) FASTLY_COMPUTE_PY="$(FASTLY_COMPUTE_PY)" uv run --extra test pytest
 
 # Update snapshots for snapshot tests
 test-update-snapshots: $(COMPOSED_WASMS)
-	VICEROY=$(VICEROY) uv run --extra test pytest --snapshot-update
+	VICEROY=$(VICEROY) FASTLY_COMPUTE_PY="$(FASTLY_COMPUTE_PY)" uv run --extra test pytest --snapshot-update
 
 # List available examples
 list-examples:

crates/fastly-compute-py/Cargo.toml

@@ -29,6 +29,7 @@ componentize-py = { git = "https://github.com/bytecodealliance/componentize-py",
 futures = { version = "0.3", default-features = false, features = ["executor"] }
 pyo3 = { version = "0.28.3", features = ["abi3-py312"], optional = true }
 serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
 toml = "0.8"
 log = "0.4"
 env_logger = "0.11"

crates/fastly-compute-py/build.rs

@@ -12,7 +12,8 @@ fn main() -> Result<()> {
  println!("cargo:rerun-if-changed=../../wrap_app_in_wasiless.wac");
  println!("cargo:rerun-if-changed=../../Cargo.lock");
 
- let root_dir = PathBuf::from("../../");
+ let manifest_dir = env::var("CARGO_MANIFEST_DIR").expect("Failed to get CARGO_MANIFEST_DIR");
+ let root_dir: PathBuf = [&manifest_dir, "..", ".."].iter().collect();
  let wit_dir = root_dir.join("wit");
  let out_dir = PathBuf::from(env::var("OUT_DIR")?);
 

crates/fastly-compute-py/src/cli.rs

@@ -36,7 +36,6 @@ pub enum Command {
  #[arg(short, long)]
  virtualenv: Option<PathBuf>,
  },
-
  /// Generate WIT binding stubs for use with type checkers and IDEs
  Bindings {
  /// WIT directory to generate bindings from (default: wit)
@@ -54,4 +53,26 @@ pub enum Command {
  /// Output directory for the generated stubs
  output_dir: PathBuf,
  },
+ /// List project dependencies in the specified format
+ Dependencies {
+ /// Output format for dependencies
+ #[arg(short, long, default_value = "json")]
+ format: DependencyFormat,
+
+ /// Write output to this file instead of stdout
+ #[arg(short, long)]
+ output: Option<PathBuf>,
+
+ /// Virtual environment in which to look for modules (default:
+ /// VIRTUAL_ENV env var or .venv)
+ #[arg(short, long)]
+ virtualenv: Option<PathBuf>,
+ },
+}
+
+#[derive(Clone, Debug, clap::ValueEnum)]
+pub enum DependencyFormat {
+ /// JSON object format: {"package-name": "1.0.0", ...}
+ /// Matches the format used in fastly_data metadata
+ Json,
 }

crates/fastly-compute-py/src/config.rs

@@ -75,6 +75,7 @@ impl ConfigBuilder {
  self.cli.virtualenv = virtualenv.clone();
  }
  Command::Bindings { .. } => {}
+ Command::Dependencies { .. } => {}
  }
  self
  }

crates/fastly-compute-py/src/dependencies.rs

@@ -0,0 +1,198 @@
+use anyhow::{Context, Result};
+use serde::{Deserialize, Serialize};
+use std::collections::HashMap;
+use std::path::PathBuf;
+use std::process::Command;
+
+/// A single package dependency with name and version
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct Dependency {
+ pub name: String,
+ pub version: String,
+}
+
+/// Fastly CLI DataCollection format for fastly_data metadata.
+/// Matches the Go structs in pkg/commands/compute/build.go.
+#[derive(Debug, Serialize)]
+pub struct FastlyData {
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub package_info: Option<PackageInfo>,
+}
+
+#[derive(Debug, Serialize)]
+pub struct PackageInfo {
+ pub packages: HashMap<String, String>,
+}
+
+/// PEP 751 pylock.toml format structures
+#[derive(Debug, Deserialize)]
+struct PylockToml {
+ #[serde(rename = "lock-version")]
+ _lock_version: String,
+ packages: Vec<PylockPackage>,
+}
+
+#[derive(Debug, Deserialize)]
+struct PylockPackage {
+ name: String,
+ /// Present for registry/VCS packages; absent for local source trees
+ /// (PEP 751: version MUST NOT be included when using a source tree)
+ version: Option<String>,
+}
+
+/// Get dependencies using UV's PEP 751 export.
+///
+/// Dependency collection only runs when both conditions are met:
+///
+/// 1. A `pyproject.toml` exists in the current directory — confirming this is
+/// a Python project that could have a lockfile. Without this, `uv export`
+/// would fail with "no pyproject.toml found" (e.g. the Viceroy test
+/// framework builds in a temp dir with no project files).
+///
+/// 2. The `UV` environment variable is set — confirming the tool was invoked
+/// via `uv run` or similar. We don't guess that `uv` should be used just
+/// because a `uv` binary happens to be on PATH; the user may be using pip,
+/// poetry, or another tool entirely.
+///
+/// When both conditions are met, errors from `uv export` are bubbled up since
+/// something genuinely went wrong in a context where UV is expected to work.
+pub fn get_dependencies(_virtualenv: &Option<PathBuf>) -> Result<Vec<Dependency>> {
+ if !std::fs::exists("pyproject.toml").unwrap_or_default() {
+ log::debug!("No pyproject.toml found, skipping dependency collection");
+ return Ok(Vec::new());
+ }
+
+ let uv_bin = match std::env::var("UV") {
+ Ok(bin) => bin,
+ Err(_) => {
+ log::debug!("UV env var not set, skipping dependency collection");
+ return Ok(Vec::new());
+ }
+ };
+
+ log::info!("Collecting dependencies from project environment...");
+
+ let deps = get_dependencies_from_uv(&uv_bin)?;
+ log::info!("Found {} dependencies via UV", deps.len());
+ Ok(deps)
+}
+
+/// Serialize dependencies as fastly_data JSON, matching the CLI's DataCollection format.
+///
+/// The build tool injects this directly so the CLI does not need to know anything
+/// about the Python environment to collect package metadata.
+pub fn get_fastly_data_json(virtualenv: &Option<PathBuf>) -> Result<String> {
+ let deps = get_dependencies(virtualenv)?;
+
+ if deps.is_empty() {
+ return Ok(String::new());
+ }
+
+ let packages: HashMap<String, String> = deps.into_iter().map(|d| (d.name, d.version)).collect();
+
+ let fastly_data = FastlyData {
+ package_info: Some(PackageInfo { packages }),
+ };
+
+ serde_json::to_string(&fastly_data).context("Failed to serialize fastly_data to JSON")
+}
+
+/// Use UV export to get dependencies in PEP 751 pylock.toml format
+fn get_dependencies_from_uv(uv_bin: &str) -> Result<Vec<Dependency>> {
+ log::debug!(
+ "Attempting to export dependencies using UV binary: {}",
+ uv_bin
+ );
+
+ let output = Command::new(uv_bin)
+ .args([
+ "export",
+ "--format",
+ "pylock.toml",
+ "--no-emit-project",
+ "--frozen",
+ "--no-header",
+ ])
+ .output()
+ .context("Failed to run 'uv export'")?;
+
+ if !output.status.success() {
+ let stderr = String::from_utf8_lossy(&output.stderr);
+ anyhow::bail!("uv export failed: {}", stderr);
+ }
+
+ let pylock_content =
+ String::from_utf8(output.stdout).context("UV output was not valid UTF-8")?;
+
+ parse_pylock_toml(&pylock_content)
+}
+
+/// Parse PEP 751 pylock.toml format
+fn parse_pylock_toml(content: &str) -> Result<Vec<Dependency>> {
+ let pylock: PylockToml =
+ toml::from_str(content).context("Failed to parse pylock.toml format")?;
+
+ let dependencies = pylock
+ .packages
+ .into_iter()
+ .map(|pkg| Dependency {
+ version: pkg.version.unwrap_or_else(|| "unknown".to_string()),
+ name: pkg.name,
+ })
+ .collect();
+
+ Ok(dependencies)
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+
+ #[test]
+ fn test_parse_versioned_packages() {
+ let sample = r#"
+lock-version = "1.0"
+created-by = "uv"
+requires-python = ">=3.12"
+
+[[packages]]
+name = "bottle"
+version = "0.13.4"
+
+[[packages]]
+name = "requests"
+version = "2.31.0"
+"#;
+
+ let deps = parse_pylock_toml(sample).unwrap();
+ assert_eq!(deps.len(), 2);
+ assert_eq!(deps[0].name, "bottle");
+ assert_eq!(deps[0].version, "0.13.4");
+ assert_eq!(deps[1].name, "requests");
+ assert_eq!(deps[1].version, "2.31.0");
+ }
+
+ #[test]
+ fn test_parse_directory_dependency_uses_unknown() {
+ // PEP 751: version MUST NOT be included for source trees.
+ // We record "unknown" so the dependency is still visible.
+ let sample = r#"
+lock-version = "1.0"
+created-by = "uv"
+requires-python = ">=3.12"
+
+[[packages]]
+name = "bottle"
+version = "0.13.4"
+
+[[packages]]
+name = "fastly-compute"
+directory = { path = "../../", editable = true }
+"#;
+
+ let deps = parse_pylock_toml(sample).unwrap();
+ assert_eq!(deps.len(), 2);
+ assert_eq!(deps[1].name, "fastly-compute");
+ assert_eq!(deps[1].version, "unknown");
+ }
+}

crates/fastly-compute-py/src/lib.rs

@@ -14,6 +14,7 @@ use wasm_metadata::AddMetadata;
 
 pub mod cli;
 pub mod config;
+pub mod dependencies;
 pub mod site_packages;
 
 use cli::Cli;
@@ -113,6 +114,34 @@ pub fn run_main(cli: &Cli) -> Result<()> {
  output_dir,
  )?;
  }
+ cli::Command::Dependencies {
+ format,
+ output,
+ virtualenv,
+ } => {
+ let deps = dependencies::get_dependencies(virtualenv)?;
+
+ match format {
+ cli::DependencyFormat::Json => {
+ // Convert to HashMap matching fastly_data packages format
+ let mut packages = std::collections::HashMap::new();
+ for dep in deps {
+ packages.insert(dep.name, dep.version);
+ }
+
+ let json = serde_json::to_string_pretty(&packages)
+ .context("Failed to serialize dependencies to JSON")?;
+
+ match output {
+ Some(path) => {
+ fs::write(path, &json)
+ .context("Failed to write dependencies to output file")?;
+ }
+ None => println!("{}", json),
+ }
+ }
+ }
+ }
  }
 
  Ok(())
@@ -223,7 +252,7 @@ pub fn build(output: PathBuf, entry_name: String, virtualenv: Option<PathBuf>) -
  compose_with_wasiless(&temp_component_wasm_path, WASILESS_WASM, WRAP_WAC, &output)?;
 
  log::info!(" Injecting Fastly metadata...");
- let annotated = inject_fastly_metadata(composed)?;
+ let annotated = inject_fastly_metadata(composed, &virtualenv)?;
 
  fs::write(&output, annotated)
  .with_context(|| format!("Failed to write output: {}", output.display()))?;
@@ -302,16 +331,18 @@ fn compose_with_wasiless(
 /// - `processed-by: componentize-py <version>` — the tool that performed the
 /// core Wasm transformation. `fastly-compute-py` also adds itself here as
 /// the build orchestrator.
+/// - `processed-by: fastly_data` — package dependency list in the same JSON
+/// format the Fastly CLI uses for all other languages. The CLI merges its
+/// own fields (build_info, machine_info, script_info) on top and skips
+/// re-collecting package_info when this key is already present.
 ///
 /// Note: the Fastly-proprietary `fastly.manifest.*` custom sections
 /// (language, version, service_id, etc.) are **not** written here. Those are
 /// injected during package ingestion, sourced from the `fastly.toml` manifest
 /// that the CLI bundles alongside the Wasm in the upload package.
-/// Dependency lists, build scripts, and machine info are similarly the CLI's
-/// responsibility via its `fastly_data` producers entry.
 ///
 /// [Producers Section spec]: https://github.com/WebAssembly/tool-conventions/blob/main/ProducersSection.md
-fn inject_fastly_metadata(wasm: Vec<u8>) -> Result<Vec<u8>> {
+fn inject_fastly_metadata(wasm: Vec<u8>, virtualenv: &Option<PathBuf>) -> Result<Vec<u8>> {
  let mut add_metadata = AddMetadata::default();
 
  // Source language. The version is the CPython version bundled by
@@ -337,6 +368,19 @@ fn inject_fastly_metadata(wasm: Vec<u8>) -> Result<Vec<u8>> {
  env!("CARGO_PKG_VERSION").to_owned(),
  ));
 
+ // Inject dependencies as fastly_data, matching the format the Fastly CLI
+ // writes for other languages. The CLI merges its own fields on top and
+ // skips re-collecting package_info when this key is already present.
+ let fastly_data_json = dependencies::get_fastly_data_json(virtualenv)?;
+ if !fastly_data_json.is_empty() {
+ log::debug!("Injecting fastly_data with package dependencies");
+ add_metadata
+ .processed_by
+ .push(("fastly_data".to_owned(), fastly_data_json));
+ } else {
+ log::debug!("No dependencies found to inject");
+ }
+
  add_metadata
  .to_wasm(&wasm)
  .context("Failed to add producers metadata to Wasm component")

fastly_compute/runtime_patching/patches.py

@@ -40,7 +40,8 @@
  # the wit_world, is around.
  def patch():
  """Pretend to patch."""
- print("Faking the run of exception-mapping monkeypatches for test runner.")
+ import sys
+ print("Faking the run of exception-mapping monkeypatches for test runner.", file=sys.stderr)
 else:
  MAPPINGS = {
  wit_world.imports.acl.AclError.GENERIC_ERROR: fastly_compute.exceptions.acl.acl_error.GenericError,

Makefile

@@ -73,11 +73,11 @@ serve: $(WASM_FILE)
 
 # Test all examples (requires all WASM files to be built)
 test: $(COMPOSED_WASMS)
-	VICEROY=$(VICEROY) uv run --extra test pytest
+	VICEROY=$(VICEROY) FASTLY_COMPUTE_PY="$(FASTLY_COMPUTE_PY)" uv run --extra test pytest
 
 # Update snapshots for snapshot tests
 test-update-snapshots: $(COMPOSED_WASMS)
-	VICEROY=$(VICEROY) uv run --extra test pytest --snapshot-update
+	VICEROY=$(VICEROY) FASTLY_COMPUTE_PY="$(FASTLY_COMPUTE_PY)" uv run --extra test pytest --snapshot-update
 
 # List available examples
 list-examples:

crates/fastly-compute-py/Cargo.toml

@@ -29,6 +29,7 @@ componentize-py = { git = "https://github.com/bytecodealliance/componentize-py",
 futures = { version = "0.3", default-features = false, features = ["executor"] }
 pyo3 = { version = "0.28.3", features = ["abi3-py312"], optional = true }
 serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
 toml = "0.8"
 log = "0.4"
 env_logger = "0.11"

crates/fastly-compute-py/build.rs

@@ -12,7 +12,8 @@ fn main() -> Result<()> {
  println!("cargo:rerun-if-changed=../../wrap_app_in_wasiless.wac");
  println!("cargo:rerun-if-changed=../../Cargo.lock");
 
- let root_dir = PathBuf::from("../../");
+ let manifest_dir = env::var("CARGO_MANIFEST_DIR").expect("Failed to get CARGO_MANIFEST_DIR");
+ let root_dir: PathBuf = [&manifest_dir, "..", ".."].iter().collect();
  let wit_dir = root_dir.join("wit");
  let out_dir = PathBuf::from(env::var("OUT_DIR")?);
 

crates/fastly-compute-py/src/cli.rs

@@ -36,7 +36,6 @@ pub enum Command {
  #[arg(short, long)]
  virtualenv: Option<PathBuf>,
  },
-
  /// Generate WIT binding stubs for use with type checkers and IDEs
  Bindings {
  /// WIT directory to generate bindings from (default: wit)
@@ -54,4 +53,26 @@ pub enum Command {
  /// Output directory for the generated stubs
  output_dir: PathBuf,
  },
+ /// List project dependencies in the specified format
+ Dependencies {
+ /// Output format for dependencies
+ #[arg(short, long, default_value = "json")]
+ format: DependencyFormat,
+
+ /// Write output to this file instead of stdout
+ #[arg(short, long)]
+ output: Option<PathBuf>,
+
+ /// Virtual environment in which to look for modules (default:
+ /// VIRTUAL_ENV env var or .venv)
+ #[arg(short, long)]
+ virtualenv: Option<PathBuf>,
+ },
+}
+
+#[derive(Clone, Debug, clap::ValueEnum)]
+pub enum DependencyFormat {
+ /// JSON object format: {"package-name": "1.0.0", ...}
+ /// Matches the format used in fastly_data metadata
+ Json,
 }

crates/fastly-compute-py/src/config.rs

@@ -75,6 +75,7 @@ impl ConfigBuilder {
  self.cli.virtualenv = virtualenv.clone();
  }
  Command::Bindings { .. } => {}
+ Command::Dependencies { .. } => {}
  }
  self
  }

crates/fastly-compute-py/src/dependencies.rs

@@ -0,0 +1,198 @@
+use anyhow::{Context, Result};
+use serde::{Deserialize, Serialize};
+use std::collections::HashMap;
+use std::path::PathBuf;
+use std::process::Command;
+
+/// A single package dependency with name and version
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct Dependency {
+ pub name: String,
+ pub version: String,
+}
+
+/// Fastly CLI DataCollection format for fastly_data metadata.
+/// Matches the Go structs in pkg/commands/compute/build.go.
+#[derive(Debug, Serialize)]
+pub struct FastlyData {
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub package_info: Option<PackageInfo>,
+}
+
+#[derive(Debug, Serialize)]
+pub struct PackageInfo {
+ pub packages: HashMap<String, String>,
+}
+
+/// PEP 751 pylock.toml format structures
+#[derive(Debug, Deserialize)]
+struct PylockToml {
+ #[serde(rename = "lock-version")]
+ _lock_version: String,
+ packages: Vec<PylockPackage>,
+}
+
+#[derive(Debug, Deserialize)]
+struct PylockPackage {
+ name: String,
+ /// Present for registry/VCS packages; absent for local source trees
+ /// (PEP 751: version MUST NOT be included when using a source tree)
+ version: Option<String>,
+}
+
+/// Get dependencies using UV's PEP 751 export.
+///
+/// Dependency collection only runs when both conditions are met:
+///
+/// 1. A `pyproject.toml` exists in the current directory — confirming this is
+/// a Python project that could have a lockfile. Without this, `uv export`
+/// would fail with "no pyproject.toml found" (e.g. the Viceroy test
+/// framework builds in a temp dir with no project files).
+///
+/// 2. The `UV` environment variable is set — confirming the tool was invoked
+/// via `uv run` or similar. We don't guess that `uv` should be used just
+/// because a `uv` binary happens to be on PATH; the user may be using pip,
+/// poetry, or another tool entirely.
+///
+/// When both conditions are met, errors from `uv export` are bubbled up since
+/// something genuinely went wrong in a context where UV is expected to work.
+pub fn get_dependencies(_virtualenv: &Option<PathBuf>) -> Result<Vec<Dependency>> {
+ if !std::fs::exists("pyproject.toml").unwrap_or_default() {
+ log::debug!("No pyproject.toml found, skipping dependency collection");
+ return Ok(Vec::new());
+ }
+
+ let uv_bin = match std::env::var("UV") {
+ Ok(bin) => bin,
+ Err(_) => {
+ log::debug!("UV env var not set, skipping dependency collection");
+ return Ok(Vec::new());
+ }
+ };
+
+ log::info!("Collecting dependencies from project environment...");
+
+ let deps = get_dependencies_from_uv(&uv_bin)?;
+ log::info!("Found {} dependencies via UV", deps.len());
+ Ok(deps)
+}
+
+/// Serialize dependencies as fastly_data JSON, matching the CLI's DataCollection format.
+///
+/// The build tool injects this directly so the CLI does not need to know anything
+/// about the Python environment to collect package metadata.
+pub fn get_fastly_data_json(virtualenv: &Option<PathBuf>) -> Result<String> {
+ let deps = get_dependencies(virtualenv)?;
+
+ if deps.is_empty() {
+ return Ok(String::new());
+ }
+
+ let packages: HashMap<String, String> = deps.into_iter().map(|d| (d.name, d.version)).collect();
+
+ let fastly_data = FastlyData {
+ package_info: Some(PackageInfo { packages }),
+ };
+
+ serde_json::to_string(&fastly_data).context("Failed to serialize fastly_data to JSON")
+}
+
+/// Use UV export to get dependencies in PEP 751 pylock.toml format
+fn get_dependencies_from_uv(uv_bin: &str) -> Result<Vec<Dependency>> {
+ log::debug!(
+ "Attempting to export dependencies using UV binary: {}",
+ uv_bin
+ );
+
+ let output = Command::new(uv_bin)
+ .args([
+ "export",
+ "--format",
+ "pylock.toml",
+ "--no-emit-project",
+ "--frozen",
+ "--no-header",
+ ])
+ .output()
+ .context("Failed to run 'uv export'")?;
+
+ if !output.status.success() {
+ let stderr = String::from_utf8_lossy(&output.stderr);
+ anyhow::bail!("uv export failed: {}", stderr);
+ }
+
+ let pylock_content =
+ String::from_utf8(output.stdout).context("UV output was not valid UTF-8")?;
+
+ parse_pylock_toml(&pylock_content)
+}
+
+/// Parse PEP 751 pylock.toml format
+fn parse_pylock_toml(content: &str) -> Result<Vec<Dependency>> {
+ let pylock: PylockToml =
+ toml::from_str(content).context("Failed to parse pylock.toml format")?;
+
+ let dependencies = pylock
+ .packages
+ .into_iter()
+ .map(|pkg| Dependency {
+ version: pkg.version.unwrap_or_else(|| "unknown".to_string()),
+ name: pkg.name,
+ })
+ .collect();
+
+ Ok(dependencies)
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+
+ #[test]
+ fn test_parse_versioned_packages() {
+ let sample = r#"
+lock-version = "1.0"
+created-by = "uv"
+requires-python = ">=3.12"
+
+[[packages]]
+name = "bottle"
+version = "0.13.4"
+
+[[packages]]
+name = "requests"
+version = "2.31.0"
+"#;
+
+ let deps = parse_pylock_toml(sample).unwrap();
+ assert_eq!(deps.len(), 2);
+ assert_eq!(deps[0].name, "bottle");
+ assert_eq!(deps[0].version, "0.13.4");
+ assert_eq!(deps[1].name, "requests");
+ assert_eq!(deps[1].version, "2.31.0");
+ }
+
+ #[test]
+ fn test_parse_directory_dependency_uses_unknown() {
+ // PEP 751: version MUST NOT be included for source trees.
+ // We record "unknown" so the dependency is still visible.
+ let sample = r#"
+lock-version = "1.0"
+created-by = "uv"
+requires-python = ">=3.12"
+
+[[packages]]
+name = "bottle"
+version = "0.13.4"
+
+[[packages]]
+name = "fastly-compute"
+directory = { path = "../../", editable = true }
+"#;
+
+ let deps = parse_pylock_toml(sample).unwrap();
+ assert_eq!(deps.len(), 2);
+ assert_eq!(deps[1].name, "fastly-compute");
+ assert_eq!(deps[1].version, "unknown");
+ }
+}

crates/fastly-compute-py/src/lib.rs

@@ -14,6 +14,7 @@ use wasm_metadata::AddMetadata;
 
 pub mod cli;
 pub mod config;
+pub mod dependencies;
 pub mod site_packages;
 
 use cli::Cli;
@@ -113,6 +114,34 @@ pub fn run_main(cli: &Cli) -> Result<()> {
  output_dir,
  )?;
  }
+ cli::Command::Dependencies {
+ format,
+ output,
+ virtualenv,
+ } => {
+ let deps = dependencies::get_dependencies(virtualenv)?;
+
+ match format {
+ cli::DependencyFormat::Json => {
+ // Convert to HashMap matching fastly_data packages format
+ let mut packages = std::collections::HashMap::new();
+ for dep in deps {
+ packages.insert(dep.name, dep.version);
+ }
+
+ let json = serde_json::to_string_pretty(&packages)
+ .context("Failed to serialize dependencies to JSON")?;
+
+ match output {
+ Some(path) => {
+ fs::write(path, &json)
+ .context("Failed to write dependencies to output file")?;
+ }
+ None => println!("{}", json),
+ }
+ }
+ }
+ }
  }
 
  Ok(())
@@ -223,7 +252,7 @@ pub fn build(output: PathBuf, entry_name: String, virtualenv: Option<PathBuf>) -
  compose_with_wasiless(&temp_component_wasm_path, WASILESS_WASM, WRAP_WAC, &output)?;
 
  log::info!(" Injecting Fastly metadata...");
- let annotated = inject_fastly_metadata(composed)?;
+ let annotated = inject_fastly_metadata(composed, &virtualenv)?;
 
  fs::write(&output, annotated)
  .with_context(|| format!("Failed to write output: {}", output.display()))?;
@@ -302,16 +331,18 @@ fn compose_with_wasiless(
 /// - `processed-by: componentize-py <version>` — the tool that performed the
 /// core Wasm transformation. `fastly-compute-py` also adds itself here as
 /// the build orchestrator.
+/// - `processed-by: fastly_data` — package dependency list in the same JSON
+/// format the Fastly CLI uses for all other languages. The CLI merges its
+/// own fields (build_info, machine_info, script_info) on top and skips
+/// re-collecting package_info when this key is already present.
 ///
 /// Note: the Fastly-proprietary `fastly.manifest.*` custom sections
 /// (language, version, service_id, etc.) are **not** written here. Those are
 /// injected during package ingestion, sourced from the `fastly.toml` manifest
 /// that the CLI bundles alongside the Wasm in the upload package.
-/// Dependency lists, build scripts, and machine info are similarly the CLI's
-/// responsibility via its `fastly_data` producers entry.
 ///
 /// [Producers Section spec]: https://github.com/WebAssembly/tool-conventions/blob/main/ProducersSection.md
-fn inject_fastly_metadata(wasm: Vec<u8>) -> Result<Vec<u8>> {
+fn inject_fastly_metadata(wasm: Vec<u8>, virtualenv: &Option<PathBuf>) -> Result<Vec<u8>> {
  let mut add_metadata = AddMetadata::default();
 
  // Source language. The version is the CPython version bundled by
@@ -337,6 +368,19 @@ fn inject_fastly_metadata(wasm: Vec<u8>) -> Result<Vec<u8>> {
  env!("CARGO_PKG_VERSION").to_owned(),
  ));
 
+ // Inject dependencies as fastly_data, matching the format the Fastly CLI
+ // writes for other languages. The CLI merges its own fields on top and
+ // skips re-collecting package_info when this key is already present.
+ let fastly_data_json = dependencies::get_fastly_data_json(virtualenv)?;
+ if !fastly_data_json.is_empty() {
+ log::debug!("Injecting fastly_data with package dependencies");
+ add_metadata
+ .processed_by
+ .push(("fastly_data".to_owned(), fastly_data_json));
+ } else {
+ log::debug!("No dependencies found to inject");
+ }
+
  add_metadata
  .to_wasm(&wasm)
  .context("Failed to add producers metadata to Wasm component")

fastly_compute/runtime_patching/patches.py

@@ -40,7 +40,8 @@
  # the wit_world, is around.
  def patch():
  """Pretend to patch."""
- print("Faking the run of exception-mapping monkeypatches for test runner.")
+ import sys
+ print("Faking the run of exception-mapping monkeypatches for test runner.", file=sys.stderr)
 else:
  MAPPINGS = {
  wit_world.imports.acl.AclError.GENERIC_ERROR: fastly_compute.exceptions.acl.acl_error.GenericError,

Makefile

@@ -73,11 +73,11 @@ serve: $(WASM_FILE)
 
 # Test all examples (requires all WASM files to be built)
 test: $(COMPOSED_WASMS)
-	VICEROY=$(VICEROY) uv run --extra test pytest
+	VICEROY=$(VICEROY) FASTLY_COMPUTE_PY="$(FASTLY_COMPUTE_PY)" uv run --extra test pytest
 
 # Update snapshots for snapshot tests
 test-update-snapshots: $(COMPOSED_WASMS)
-	VICEROY=$(VICEROY) uv run --extra test pytest --snapshot-update
+	VICEROY=$(VICEROY) FASTLY_COMPUTE_PY="$(FASTLY_COMPUTE_PY)" uv run --extra test pytest --snapshot-update
 
 # List available examples
 list-examples:

crates/fastly-compute-py/Cargo.toml

@@ -29,6 +29,7 @@ componentize-py = { git = "https://github.com/bytecodealliance/componentize-py",
 futures = { version = "0.3", default-features = false, features = ["executor"] }
 pyo3 = { version = "0.28.3", features = ["abi3-py312"], optional = true }
 serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
 toml = "0.8"
 log = "0.4"
 env_logger = "0.11"

crates/fastly-compute-py/build.rs

@@ -12,7 +12,8 @@ fn main() -> Result<()> {
  println!("cargo:rerun-if-changed=../../wrap_app_in_wasiless.wac");
  println!("cargo:rerun-if-changed=../../Cargo.lock");
 
- let root_dir = PathBuf::from("../../");
+ let manifest_dir = env::var("CARGO_MANIFEST_DIR").expect("Failed to get CARGO_MANIFEST_DIR");
+ let root_dir: PathBuf = [&manifest_dir, "..", ".."].iter().collect();
  let wit_dir = root_dir.join("wit");
  let out_dir = PathBuf::from(env::var("OUT_DIR")?);
 

crates/fastly-compute-py/src/cli.rs

@@ -36,7 +36,6 @@ pub enum Command {
  #[arg(short, long)]
  virtualenv: Option<PathBuf>,
  },
-
  /// Generate WIT binding stubs for use with type checkers and IDEs
  Bindings {
  /// WIT directory to generate bindings from (default: wit)
@@ -54,4 +53,26 @@ pub enum Command {
  /// Output directory for the generated stubs
  output_dir: PathBuf,
  },
+ /// List project dependencies in the specified format
+ Dependencies {
+ /// Output format for dependencies
+ #[arg(short, long, default_value = "json")]
+ format: DependencyFormat,
+
+ /// Write output to this file instead of stdout
+ #[arg(short, long)]
+ output: Option<PathBuf>,
+
+ /// Virtual environment in which to look for modules (default:
+ /// VIRTUAL_ENV env var or .venv)
+ #[arg(short, long)]
+ virtualenv: Option<PathBuf>,
+ },
+}
+
+#[derive(Clone, Debug, clap::ValueEnum)]
+pub enum DependencyFormat {
+ /// JSON object format: {"package-name": "1.0.0", ...}
+ /// Matches the format used in fastly_data metadata
+ Json,
 }

crates/fastly-compute-py/src/config.rs

@@ -75,6 +75,7 @@ impl ConfigBuilder {
  self.cli.virtualenv = virtualenv.clone();
  }
  Command::Bindings { .. } => {}
+ Command::Dependencies { .. } => {}
  }
  self
  }

crates/fastly-compute-py/src/dependencies.rs

@@ -0,0 +1,198 @@
+use anyhow::{Context, Result};
+use serde::{Deserialize, Serialize};
+use std::collections::HashMap;
+use std::path::PathBuf;
+use std::process::Command;
+
+/// A single package dependency with name and version
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct Dependency {
+ pub name: String,
+ pub version: String,
+}
+
+/// Fastly CLI DataCollection format for fastly_data metadata.
+/// Matches the Go structs in pkg/commands/compute/build.go.
+#[derive(Debug, Serialize)]
+pub struct FastlyData {
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub package_info: Option<PackageInfo>,
+}
+
+#[derive(Debug, Serialize)]
+pub struct PackageInfo {
+ pub packages: HashMap<String, String>,
+}
+
+/// PEP 751 pylock.toml format structures
+#[derive(Debug, Deserialize)]
+struct PylockToml {
+ #[serde(rename = "lock-version")]
+ _lock_version: String,
+ packages: Vec<PylockPackage>,
+}
+
+#[derive(Debug, Deserialize)]
+struct PylockPackage {
+ name: String,
+ /// Present for registry/VCS packages; absent for local source trees
+ /// (PEP 751: version MUST NOT be included when using a source tree)
+ version: Option<String>,
+}
+
+/// Get dependencies using UV's PEP 751 export.
+///
+/// Dependency collection only runs when both conditions are met:
+///
+/// 1. A `pyproject.toml` exists in the current directory — confirming this is
+/// a Python project that could have a lockfile. Without this, `uv export`
+/// would fail with "no pyproject.toml found" (e.g. the Viceroy test
+/// framework builds in a temp dir with no project files).
+///
+/// 2. The `UV` environment variable is set — confirming the tool was invoked
+/// via `uv run` or similar. We don't guess that `uv` should be used just
+/// because a `uv` binary happens to be on PATH; the user may be using pip,
+/// poetry, or another tool entirely.
+///
+/// When both conditions are met, errors from `uv export` are bubbled up since
+/// something genuinely went wrong in a context where UV is expected to work.
+pub fn get_dependencies(_virtualenv: &Option<PathBuf>) -> Result<Vec<Dependency>> {
+ if !std::fs::exists("pyproject.toml").unwrap_or_default() {
+ log::debug!("No pyproject.toml found, skipping dependency collection");
+ return Ok(Vec::new());
+ }
+
+ let uv_bin = match std::env::var("UV") {
+ Ok(bin) => bin,
+ Err(_) => {
+ log::debug!("UV env var not set, skipping dependency collection");
+ return Ok(Vec::new());
+ }
+ };
+
+ log::info!("Collecting dependencies from project environment...");
+
+ let deps = get_dependencies_from_uv(&uv_bin)?;
+ log::info!("Found {} dependencies via UV", deps.len());
+ Ok(deps)
+}
+
+/// Serialize dependencies as fastly_data JSON, matching the CLI's DataCollection format.
+///
+/// The build tool injects this directly so the CLI does not need to know anything
+/// about the Python environment to collect package metadata.
+pub fn get_fastly_data_json(virtualenv: &Option<PathBuf>) -> Result<String> {
+ let deps = get_dependencies(virtualenv)?;
+
+ if deps.is_empty() {
+ return Ok(String::new());
+ }
+
+ let packages: HashMap<String, String> = deps.into_iter().map(|d| (d.name, d.version)).collect();
+
+ let fastly_data = FastlyData {
+ package_info: Some(PackageInfo { packages }),
+ };
+
+ serde_json::to_string(&fastly_data).context("Failed to serialize fastly_data to JSON")
+}
+
+/// Use UV export to get dependencies in PEP 751 pylock.toml format
+fn get_dependencies_from_uv(uv_bin: &str) -> Result<Vec<Dependency>> {
+ log::debug!(
+ "Attempting to export dependencies using UV binary: {}",
+ uv_bin
+ );
+
+ let output = Command::new(uv_bin)
+ .args([
+ "export",
+ "--format",
+ "pylock.toml",
+ "--no-emit-project",
+ "--frozen",
+ "--no-header",
+ ])
+ .output()
+ .context("Failed to run 'uv export'")?;
+
+ if !output.status.success() {
+ let stderr = String::from_utf8_lossy(&output.stderr);
+ anyhow::bail!("uv export failed: {}", stderr);
+ }
+
+ let pylock_content =
+ String::from_utf8(output.stdout).context("UV output was not valid UTF-8")?;
+
+ parse_pylock_toml(&pylock_content)
+}
+
+/// Parse PEP 751 pylock.toml format
+fn parse_pylock_toml(content: &str) -> Result<Vec<Dependency>> {
+ let pylock: PylockToml =
+ toml::from_str(content).context("Failed to parse pylock.toml format")?;
+
+ let dependencies = pylock
+ .packages
+ .into_iter()
+ .map(|pkg| Dependency {
+ version: pkg.version.unwrap_or_else(|| "unknown".to_string()),
+ name: pkg.name,
+ })
+ .collect();
+
+ Ok(dependencies)
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+
+ #[test]
+ fn test_parse_versioned_packages() {
+ let sample = r#"
+lock-version = "1.0"
+created-by = "uv"
+requires-python = ">=3.12"
+
+[[packages]]
+name = "bottle"
+version = "0.13.4"
+
+[[packages]]
+name = "requests"
+version = "2.31.0"
+"#;
+
+ let deps = parse_pylock_toml(sample).unwrap();
+ assert_eq!(deps.len(), 2);
+ assert_eq!(deps[0].name, "bottle");
+ assert_eq!(deps[0].version, "0.13.4");
+ assert_eq!(deps[1].name, "requests");
+ assert_eq!(deps[1].version, "2.31.0");
+ }
+
+ #[test]
+ fn test_parse_directory_dependency_uses_unknown() {
+ // PEP 751: version MUST NOT be included for source trees.
+ // We record "unknown" so the dependency is still visible.
+ let sample = r#"
+lock-version = "1.0"
+created-by = "uv"
+requires-python = ">=3.12"
+
+[[packages]]
+name = "bottle"
+version = "0.13.4"
+
+[[packages]]
+name = "fastly-compute"
+directory = { path = "../../", editable = true }
+"#;
+
+ let deps = parse_pylock_toml(sample).unwrap();
+ assert_eq!(deps.len(), 2);
+ assert_eq!(deps[1].name, "fastly-compute");
+ assert_eq!(deps[1].version, "unknown");
+ }
+}

crates/fastly-compute-py/src/lib.rs

@@ -14,6 +14,7 @@ use wasm_metadata::AddMetadata;
 
 pub mod cli;
 pub mod config;
+pub mod dependencies;
 pub mod site_packages;
 
 use cli::Cli;
@@ -113,6 +114,34 @@ pub fn run_main(cli: &Cli) -> Result<()> {
  output_dir,
  )?;
  }
+ cli::Command::Dependencies {
+ format,
+ output,
+ virtualenv,
+ } => {
+ let deps = dependencies::get_dependencies(virtualenv)?;
+
+ match format {
+ cli::DependencyFormat::Json => {
+ // Convert to HashMap matching fastly_data packages format
+ let mut packages = std::collections::HashMap::new();
+ for dep in deps {
+ packages.insert(dep.name, dep.version);
+ }
+
+ let json = serde_json::to_string_pretty(&packages)
+ .context("Failed to serialize dependencies to JSON")?;
+
+ match output {
+ Some(path) => {
+ fs::write(path, &json)
+ .context("Failed to write dependencies to output file")?;
+ }
+ None => println!("{}", json),
+ }
+ }
+ }
+ }
  }
 
  Ok(())
@@ -223,7 +252,7 @@ pub fn build(output: PathBuf, entry_name: String, virtualenv: Option<PathBuf>) -
  compose_with_wasiless(&temp_component_wasm_path, WASILESS_WASM, WRAP_WAC, &output)?;
 
  log::info!(" Injecting Fastly metadata...");
- let annotated = inject_fastly_metadata(composed)?;
+ let annotated = inject_fastly_metadata(composed, &virtualenv)?;
 
  fs::write(&output, annotated)
  .with_context(|| format!("Failed to write output: {}", output.display()))?;
@@ -302,16 +331,18 @@ fn compose_with_wasiless(
 /// - `processed-by: componentize-py <version>` — the tool that performed the
 /// core Wasm transformation. `fastly-compute-py` also adds itself here as
 /// the build orchestrator.
+/// - `processed-by: fastly_data` — package dependency list in the same JSON
+/// format the Fastly CLI uses for all other languages. The CLI merges its
+/// own fields (build_info, machine_info, script_info) on top and skips
+/// re-collecting package_info when this key is already present.
 ///
 /// Note: the Fastly-proprietary `fastly.manifest.*` custom sections
 /// (language, version, service_id, etc.) are **not** written here. Those are
 /// injected during package ingestion, sourced from the `fastly.toml` manifest
 /// that the CLI bundles alongside the Wasm in the upload package.
-/// Dependency lists, build scripts, and machine info are similarly the CLI's
-/// responsibility via its `fastly_data` producers entry.
 ///
 /// [Producers Section spec]: https://github.com/WebAssembly/tool-conventions/blob/main/ProducersSection.md
-fn inject_fastly_metadata(wasm: Vec<u8>) -> Result<Vec<u8>> {
+fn inject_fastly_metadata(wasm: Vec<u8>, virtualenv: &Option<PathBuf>) -> Result<Vec<u8>> {
  let mut add_metadata = AddMetadata::default();
 
  // Source language. The version is the CPython version bundled by
@@ -337,6 +368,19 @@ fn inject_fastly_metadata(wasm: Vec<u8>) -> Result<Vec<u8>> {
  env!("CARGO_PKG_VERSION").to_owned(),
  ));
 
+ // Inject dependencies as fastly_data, matching the format the Fastly CLI
+ // writes for other languages. The CLI merges its own fields on top and
+ // skips re-collecting package_info when this key is already present.
+ let fastly_data_json = dependencies::get_fastly_data_json(virtualenv)?;
+ if !fastly_data_json.is_empty() {
+ log::debug!("Injecting fastly_data with package dependencies");
+ add_metadata
+ .processed_by
+ .push(("fastly_data".to_owned(), fastly_data_json));
+ } else {
+ log::debug!("No dependencies found to inject");
+ }
+
  add_metadata
  .to_wasm(&wasm)
  .context("Failed to add producers metadata to Wasm component")

fastly_compute/runtime_patching/patches.py

@@ -40,7 +40,8 @@
  # the wit_world, is around.
  def patch():
  """Pretend to patch."""
- print("Faking the run of exception-mapping monkeypatches for test runner.")
+ import sys
+ print("Faking the run of exception-mapping monkeypatches for test runner.", file=sys.stderr)
 else:
  MAPPINGS = {
  wit_world.imports.acl.AclError.GENERIC_ERROR: fastly_compute.exceptions.acl.acl_error.GenericError,