Auto merge of #118368 - GuillaumeGomez:env-flag, r=Nilstrieb

Implement `--env` compiler flag (without `tracked_env` support)
Part of #80792.
Implementation of rust-lang/compiler-team#653.
Not an implementation of rust-lang/rfcs#2794.
It adds the `--env` compiler flag option which allows to set environment values used by `env!` and `option_env!`.
Important to note: When trying to retrieve an environment variable value, it will first look into the ones defined with `--env`, and if there isn't one, then only it will look into the environment variables. So if you use `--env PATH=a`, then `env!("PATH")` will return `"a"` and not the actual `PATH` value.
As mentioned in the title, `tracked_env` support is not added here. I'll do it in a follow-up PR.
r? rust-lang/compiler

Author: bors

compiler/rustc_builtin_macros/src/env.rs

@@ -13,6 +13,16 @@ use thin_vec::thin_vec;
 
 usecrate::errors;
 
+fnlookup_env<'cx>(cx:&'cxExtCtxt<'_>,var:Symbol) -> Option<Symbol>{
+let var = var.as_str();
+ifletSome(value) = cx.sess.opts.logical_env.get(var){
+returnSome(Symbol::intern(value));
+}
+// If the environment variable was not defined with the `--env` option, we try to retrieve it
+// from rustc's environment.
+ env::var(var).ok().as_deref().map(Symbol::intern)
+}
+
 pubfnexpand_option_env<'cx>(
 cx:&'cxmutExtCtxt<'_>,
 sp:Span,
@@ -23,7 +33,7 @@ pub fn expand_option_env<'cx>(
 };
 
 let sp = cx.with_def_site_ctxt(sp);
-let value = env::var(var.as_str()).ok().as_deref().map(Symbol::intern);
+let value = lookup_env(cx,var);
  cx.sess.parse_sess.env_depinfo.borrow_mut().insert((var, value));
 let e = match value {
 None => {
@@ -77,7 +87,7 @@ pub fn expand_env<'cx>(
 };
 
 let span = cx.with_def_site_ctxt(sp);
-let value = env::var(var.as_str()).ok().as_deref().map(Symbol::intern);
+let value = lookup_env(cx,var);
  cx.sess.parse_sess.env_depinfo.borrow_mut().insert((var, value));
 let e = match value {
 None => {

compiler/rustc_session/src/config.rs

@@ -8,7 +8,7 @@ use crate::search_paths::SearchPath;
 usecrate::utils::{CanonicalizedPath,NativeLib,NativeLibKind};
 usecrate::{lint,HashStableContext};
 usecrate::{EarlyErrorHandler,Session};
-use rustc_data_structures::fx::{FxHashMap,FxHashSet,FxIndexSet};
+use rustc_data_structures::fx::{FxHashMap,FxHashSet,FxIndexMap,FxIndexSet};
 use rustc_data_structures::stable_hasher::{StableOrd,ToStableHashKey};
 use rustc_errors::emitter::HumanReadableErrorType;
 use rustc_errors::{ColorConfig,DiagnosticArgValue,HandlerFlags,IntoDiagnosticArg};
@@ -1114,6 +1114,7 @@ impl Default for Options {
 pretty:None,
 working_dir:RealFileName::LocalPath(std::env::current_dir().unwrap()),
 color:ColorConfig::Auto,
+logical_env:FxIndexMap::default(),
 }
 }
 }
@@ -1813,6 +1814,7 @@ pub fn rustc_optgroups() -> Vec<RustcOptGroup> {
 "Remap source names in all output (compiler messages and output files)",
 "FROM=TO",
 ),
+ opt::multi("","env","Inject an environment variable","VAR=VALUE"),
 ]);
  opts
 }
@@ -2592,6 +2594,23 @@ fn parse_remap_path_prefix(
  mapping
 }
 
+fnparse_logical_env(
+handler:&mutEarlyErrorHandler,
+matches:&getopts::Matches,
+) -> FxIndexMap<String,String>{
+letmut vars = FxIndexMap::default();
+
+for arg in matches.opt_strs("env"){
+ifletSome((name, val)) = arg.split_once('='){
+ vars.insert(name.to_string(), val.to_string());
+}else{
+ handler.early_error(format!("`--env`: specify value for variable `{arg}`"));
+}
+}
+
+ vars
+}
+
 // JUSTIFICATION: before wrapper fn is available
 #[allow(rustc::bad_opt_access)]
 pubfnbuild_session_options(
@@ -2830,6 +2849,8 @@ pub fn build_session_options(
  handler.early_error("can't dump dependency graph without `-Z query-dep-graph`");
 }
 
+let logical_env = parse_logical_env(handler, matches);
+
 // Try to find a directory containing the Rust `src`, for more details see
 // the doc comment on the `real_rust_source_base_dir` field.
 let tmp_buf;
@@ -2910,6 +2931,7 @@ pub fn build_session_options(
  pretty,
  working_dir,
  color,
+ logical_env,
 }
 }
 
@@ -3184,6 +3206,7 @@ pub(crate) mod dep_tracking {
 };
 usecrate::lint;
 usecrate::utils::NativeLib;
+use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::stable_hasher::Hash64;
 use rustc_errors::LanguageIdentifier;
 use rustc_feature::UnstableFeatures;
@@ -3342,6 +3365,21 @@ pub(crate) mod dep_tracking {
 }
 }
 
+impl<T:DepTrackingHash,V:DepTrackingHash>DepTrackingHashforFxIndexMap<T,V>{
+fnhash(
+&self,
+hasher:&mutDefaultHasher,
+error_format:ErrorOutputType,
+for_crate_hash:bool,
+){
+Hash::hash(&self.len(), hasher);
+for(key, value)inself.iter(){
+DepTrackingHash::hash(key, hasher, error_format, for_crate_hash);
+DepTrackingHash::hash(value, hasher, error_format, for_crate_hash);
+}
+}
+}
+
 implDepTrackingHashforOutputTypes{
 fnhash(
 &self,

compiler/rustc_session/src/options.rs

@@ -3,6 +3,7 @@ use crate::config::*;
 usecrate::search_paths::SearchPath;
 usecrate::utils::NativeLib;
 usecrate::{lint,EarlyErrorHandler};
+use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::profiling::TimePassesFormat;
 use rustc_data_structures::stable_hasher::Hash64;
 use rustc_errors::ColorConfig;
@@ -150,6 +151,9 @@ top_level_options!(
 
  target_triple:TargetTriple[TRACKED],
 
+/// Effective logical environment used by `env!`/`option_env!` macros
+ logical_env:FxIndexMap<String,String> [TRACKED],
+
  test:bool[TRACKED],
  error_format:ErrorOutputType[UNTRACKED],
  diagnostic_width:Option<usize> [UNTRACKED],

src/doc/unstable-book/src/compiler-flags/env.md

@@ -0,0 +1,26 @@
+# `env`
+
+The tracking issue for this feature is: [#118372](https://github.com/rust-lang/rust/issues/118372).
+
+------------------------
+
+This option flag allows to specify environment variables value at compile time to be
+used by `env!` and `option_env!` macros.
+
+When retrieving an environment variable value, the one specified by `--env` will take
+precedence. For example, if you want have `PATH=a` in your environment and pass:
+
+```bash
+rustc --env PATH=env
+```
+
+Then you will have:
+
+```rust,no_run
+assert_eq!(env!("PATH"), "env");
+```
+
+Please note that on Windows, environment variables are case insensitive but case
+preserving whereas `rustc`'s environment variables are case sensitive. For example,
+having `Path` in your environment (case insensitive) is different than using
+`rustc --env Path=...` (case sensitive).

tests/ui/extenv/extenv-env-overload.rs

@@ -0,0 +1,9 @@
+// run-pass
+// rustc-env:MY_VAR=tadam
+// compile-flags: --env MY_VAR=123abc -Zunstable-options
+
+// This test ensures that variables provided with `--env` take precedence over
+// variables from environment.
+fnmain(){
+assert_eq!(env!("MY_VAR"),"123abc");
+}

tests/ui/extenv/extenv-env.rs

@@ -0,0 +1,5 @@
+// compile-flags: --env FOO=123abc -Zunstable-options
+// run-pass
+fnmain(){
+assert_eq!(env!("FOO"),"123abc");
+}

tests/ui/extenv/extenv-not-env.rs

@@ -0,0 +1,7 @@
+// run-pass
+// rustc-env:MY_ENV=/
+// Ensures that variables not defined through `--env` are still available.
+
+fnmain(){
+assert!(!env!("MY_ENV").is_empty());
+}

tests/ui/feature-gates/env-flag.rs

@@ -0,0 +1,3 @@
+// compile-flags: --env A=B
+
+fnmain(){}

tests/ui/feature-gates/env-flag.stderr

@@ -0,0 +1,2 @@
+error: the `-Z unstable-options` flag must also be passed to enable the flag `env`
+