rules_wasm_component

^{Bazel rules for WebAssembly Component Model}

Production-ready Bazel rules for building WebAssembly components across multiple languages with native WASI 0.2 support.

Note

Part of the PulseEngine toolchain. Used across all PulseEngine projects for hermetic component builds.

Why Use This?

• Multi-language: Build components from Rust, Go (TinyGo), C++, JavaScript/TypeScript
• Production Ready: OCI publishing, cryptographic signing, WAC composition, AOT compilation
• Bazel Native: Hermetic builds, aggressive caching, cross-platform (Windows/macOS/Linux)
• Zero Shell Scripts: Pure Bazel implementation for maximum portability

Installation

Add to your MODULE.bazel:

bazel_dep(name="rules_wasm_component", version="1.0.0")

Quick Examples

Rust Component

load("@rules_wasm_component//rust:defs.bzl", "rust_wasm_component")
rust_wasm_component(
name="my_service",
srcs= ["src/lib.rs"],
wit=":service_wit",
profiles= ["debug", "release"],
)

Go Component (TinyGo 0.39.0+)

load("@rules_wasm_component//go:defs.bzl", "go_wasm_component")
go_wasm_component(
name="calculator",
srcs= ["main.go"],
wit=":calculator_wit",
world="calculator",
)

C++ Component (WASI SDK 27+)

load("@rules_wasm_component//cpp:defs.bzl", "cpp_component")
cpp_component(
name="calculator",
srcs= ["calculator.cpp"],
wit=":calculator_wit",
cxx_std="c++20",
)

WAC Composition

load("@rules_wasm_component//wac:defs.bzl", "wac_compose")
wac_compose(
name="full_system",
components= {
":frontend": "app:frontend",
":backend": "app:backend",
},
composition=''' let frontend = new app:frontend { ... }; let backend = new app:backend { ... }; connect frontend.request -> backend.handler; export frontend as main; ''',
)

Features

Language Support

• Rust (1.90.0+): Multi-profile builds, Clippy integration, Wizer pre-initialization
• Go (TinyGo 0.39.0): Native WASI 0.2, hermetic Go module resolution
• C++ (WASI SDK 27): C++17/20/23, cross-package headers, LTO optimization
• JavaScript/TypeScript (jco 1.4.0, Node.js 20.18.0): NPM dependencies, componentize-js

Production Features

• WAC Composition: Official WebAssembly Composition standard for multi-component systems
• OCI Publishing: Push components to Docker/OCI registries
• Cryptographic Signing: wasmsign2 integration for supply chain security
• AOT Compilation: Wasmtime precompilation for 87% size reduction and faster startup
• Wizer Pre-initialization: 1.35-6x startup improvement for Rust components
• Multi-Profile Builds: Debug, release, and custom optimization profiles

Developer Experience

• Hermetic Toolchains: All tools downloaded automatically, no system dependencies
• Cross-Platform: Native Windows/macOS/Linux support without WSL
• Comprehensive Examples: 20+ working examples from basic to advanced patterns

Toolchain Versions

See MODULE.bazel for current versions — the single source of truth.

All toolchains are hermetically downloaded and version-pinned for reproducible builds.

Documentation

Complete Rule Reference — All rules, attributes, and providers

Guides:

• Toolchain Configuration
• Multi-Profile Builds
• Development Guidelines

Examples:

• Basic Component
• Multi-Language Composition
• Wizer Pre-initialization
• OCI Publishing
• See all examples

Known Limitations

Go WIT Components (Temporary)

• WIT-enabled Go components currently fail due to upstream TinyGo limitations
• Tracking: Issue #82
• Basic Go components (without WIT) work perfectly

C++ Exception Handling

• WASI disables C++ exceptions by default for size/performance
• Use enable_exceptions = True for components that require exceptions (Issue #83)

Contributing

Contributions welcome! See CONTRIBUTING.md for details.

License

Apache-2.0 — see LICENSE.

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_{Part of the PulseEngine toolchain.}