WASM Build

Skill Lab uses @ast-grep/wasm for cross-platform code analysis. Because this package is not yet published to npm, it is built from source and placed in vendor/ast-grep-wasm/ at the repo root.

The vendor/ directory is gitignored and must be regenerated by running:

deno task setup

This must be done before running check, test, or build.

---

Prerequisites

• Rust (stable toolchain) — rustup.rs
• wasm-pack — rustwasm.github.io/wasm-pack
• Deno v2.x — deno.land

Install wasm-pack:

curl https://rustwasm.github.io/wasm-pack/installer/init.sh -sSf | sh

Make sure the wasm32-unknown-unknown Rust target is installed:

rustup target add wasm32-unknown-unknown

---

What deno task setup does

The setup script is scripts/setup_wasm.ts. It:

1. Clones the ast-grep repository (no-checkout, shallow) into /tmp/ast-grep-wasm-build
2. Checks out the pinned commit 3392cb5b0b53887db618866d95a41893c1575cb6 from PR #2484
3. Runs wasm-pack build --target nodejs --out-dir pkg in crates/wasm/
4. Copies ast_grep_wasm_bg.wasm and ast_grep_wasm.js to vendor/ast-grep-wasm/
5. Writes a minimal package.json to vendor/ast-grep-wasm/ for Deno module resolution

The build typically takes 2–5 minutes on first run (Rust compilation). Subsequent runs are fast if the Cargo cache (~/.cargo/registry) is warm.

---

Version pinning

The pinned commit (3392cb5b) corresponds to a specific point on the wasm branch. When updating to a newer commit:

1. Update PINNED_COMMIT in scripts/setup_wasm.ts
2. Verify web-tree-sitter ABI compatibility (see below)
3. Re-run deno task setup

web-tree-sitter version pinning

web-tree-sitter is pinned to exact version 0.25.4 in packages/analyzer/deno.json. This is intentional — grammar .wasm files are compiled by the tree-sitter CLI against a specific WASM ABI. Mixing a grammar file compiled for one ABI version with a different web-tree-sitter runtime version causes silent parse failures (no error is thrown; the parsed tree is silently wrong).

Grammar .wasm files used by Skill Lab (from packages/analyzer/treesitter/registry.ts):

Language	Version	Source
bash	0.25.1	tree-sitter/tree-sitter-bash
javascript	0.25.0	tree-sitter/tree-sitter-javascript
python	0.25.0	tree-sitter/tree-sitter-python
typescript / tsx	0.23.2	tree-sitter/tree-sitter-typescript
markdown	0.5.2	tree-sitter-grammars/tree-sitter-markdown
markdown-inline	0.5.2	tree-sitter-grammars/tree-sitter-markdown

If you update web-tree-sitter, you must also update all grammar URLs and verify ABI compatibility with the new runtime version.

---

Grammar file size

Each grammar .wasm file is approximately 1.3–1.4 MB — comparable in size to a single platform-specific .so file. The previous approach bundled four platform .so files per language into each release archive (~5 MB per language). With WASM, a single file serves all platforms, and grammars are downloaded on first use rather than bundled into the release archive.

Grammar files are cached locally in the XDG cache directory.

---

CI

The GitHub Actions workflow (.github/workflows/cli.yml) runs deno task setup before every build and test job. Rust build artifacts are cached using actions/cache keyed on Cargo.lock.