Migrate from standalone Wizer to wasmtime-wizer

[avrabe]

Summary

The standalone Wizer project has been merged upstream into Wasmtime as of v39.0.0 (November 20, 2025).

Current State

Our tools/wizer_initializer is currently a placeholder implementation that:

• Detects WebAssembly component vs module format
• Has the architecture for component → module → wizer → component workflow
• Does NOT actually perform pre-initialization (returns input as-is)

The wizer crate dependency was never added due to complex dependency conflicts with Cranelift/Wasmtime in Bazel's crate_universe.

New Upstream Solution

Wasmtime v39.0.0+ provides:

CLI: wasmtime wizer

wasmtime wizer --init-func wizer-initialize input.wasm -o output.wasm

Crate: wasmtime-wizer

• Available as part of the Wasmtime ecosystem
• Better maintained as part of the main Wasmtime project
• Integrated with Wasmtime's component model support

Breaking Changes

• Init function name changed from wizer.initialize to wizer-initialize (compatible with components)
• The component-init project was also merged into this

Proposed Migration

Option 1: Use wasmtime wizer CLI (Recommended)

Since we already have a Wasmtime toolchain (//toolchains:wasmtime_toolchain), we can:

1. Update wasm_component_wizer_library rule to invoke wasmtime wizer subcommand
2. Remove the wizer_initializer Rust tool (keep checksum_updater as separate package)
3. Update init function references from wizer.initialize to wizer-initialize

Option 2: Use wasmtime-wizer crate

If library-level integration is needed:

1. Add wasmtime-wizer to crate dependencies
2. Implement actual pre-initialization in wizer_initializer
3. Handle component model integration

Tasks

• Evaluate which option best fits the project needs
• Update wasm/wasm_component_wizer_library.bzl to use wasmtime wizer
• Split checksum_updater into separate package (it has different dependencies)
• Update documentation for new init function name
• Test with existing wizer examples
• Remove deprecated wizer_initializer tool once migration complete

References

• Wasmtime v39.0.0 Release Notes
• wasmtime-wizer API docs
• Original Wizer repository (now archived/redirects)
• component-init (also merged)