Bazel Rules for WebAssembly Component Model

Modern Bazel rules for building and composing WebAssembly components.

Features

• 🚀 Component Model Support: Full support for WASM Component Model and WIT
• 🦀 Rust Integration: Seamless integration with rules_rust
• 🔧 Toolchain Management: Automatic wasm-tools and wit-bindgen setup
• 📦 Composition: WAC-based component composition
• 🎯 Type Safety: Strongly typed WIT interfaces
• ⚡ Performance: Optimized builds with proper caching

Installation

Add to your MODULE.bazel:

bazel_dep(name = "rules_wasm_component", version = "0.1.0")

# Optional: Configure WASM toolchain version
wasm_toolchain = use_extension(
    "@rules_wasm_component//wasm:extensions.bzl",
    "wasm_toolchain",
)
wasm_toolchain.register(
    name = "wasm_tools",
    version = "1.0.60",  # Optional, defaults to latest stable
)

Quick Start

1. Define WIT Interfaces

load("@rules_wasm_component//wit:defs.bzl", "wit_library")

wit_library(
    name = "my_interfaces",
    srcs = ["my-interface.wit"],
    deps = ["//wit/deps:wasi-io"],
)

2. Build Rust WASM Component

load("@rules_wasm_component//rust:defs.bzl", "rust_wasm_component")

rust_wasm_component(
    name = "my_component",
    srcs = ["src/lib.rs"],
    wit_bindgen = ":my_interfaces",
    deps = [
        "//third_party/rust:wit_bindgen",
    ],
)

3. Compose Components

load("@rules_wasm_component//wac:defs.bzl", "wac_compose")

wac_compose(
    name = "my_system",
    components = {
        "frontend": ":frontend_component",
        "backend": ":backend_component",
    },
    composition = """
        let frontend = new frontend:component { ... };
        let backend = new backend:component { ... };
        
        connect frontend.request -> backend.handler;
        
        export frontend as main;
    """,
)

Rules

WIT Rules

• wit_library - Process WIT interface files
• wit_bindgen - Generate language bindings from WIT

Rust Rules

• rust_wasm_component - Build Rust WASM components
• rust_wasm_component_test - Test WASM components

Composition Rules

• wac_compose - Compose multiple components
• wasm_component_new - Convert modules to components

Analysis Rules

• wasm_validate - Validate WASM components
• wit_lint - Lint WIT interfaces

Examples

See the examples/ directory for complete examples:

• Basic Component - Simple component with WIT
• Composition - Multi-component system
• WASI Integration - Using WASI interfaces
• Testing - Component testing patterns

Documentation

For Developers

• Rule Reference
• Migration Guide
• Best Practices
• Troubleshooting

For AI Agents

• AI Agent Guide - Structured documentation for AI coding assistants
• Rule Schemas - Machine-readable rule definitions
• Examples - Progressive complexity examples:
  • Basic - Fundamental patterns
  • Intermediate - Cross-package dependencies
  • Advanced - Complex compositions and custom rules

Contributing

Contributions are welcome! Please read our Contributing Guide.

License

Apache 2.0 - See LICENSE for details.