Codemod

Codemod

Use pinned ts-morph for TypeScript and TSX migrations. A codemod is a complete migration recipe, not merely a rename map: it combines deterministic AST transforms with enough semantic guidance for an agent to rewrite call sites that cannot be changed mechanically.

Establish whether a migration exists

Before authoring a recipe for repository-owned API work, determine whether the affected surface exists on the remote default branch, a released tag, or another externally consumed canary. If the symbol or call shape exists only in the current unmerged branch or worktree, there is no consumer migration to preserve: edit the source and its in-repository call sites directly, and do not create or archive a codemod. A public-looking declaration is not a migration surface until it has been merged or otherwise shared with consumers.

Use a codemod once compatibility evidence exists, or when the user explicitly asks to preserve a migration recipe. When history is ambiguous, inspect the remote default branch and release/canary history before choosing the heavier workflow.

Choose a mode

• Apply an archived codemod: list the archive, select every recipe after the caller's current canary, and read each recipe's recipe.json and instructions.md completely before changing files.
• Author a codemod: read references/recipe-format.md, create one dated recipe, test its automatic transform, and prove its agent-directed steps against real call sites.
• Rename landed or externally consumed repository symbols: author the dated recipe first, then apply it to this repository. The recipe is the durable record and consumer migration aid; an ignored one-off script is not sufficient.
• Rename unmerged work-in-progress symbols: update the source and current in-repository call sites directly. Do not manufacture a migration archive for an API no consumer could have used.

List archived recipes without loading their instructions:

mise exec -- node .agents/skills/codemod/scripts/list-codemods.mjs

Verify that every archived migration is already applied, or apply the complete archive in lexical order:

mise exec -- node .agents/skills/codemod/scripts/run-all-codemods.mjs \
  --project path/to/tsconfig.json --target path/to/project --check
mise exec -- node .agents/skills/codemod/scripts/run-all-codemods.mjs \
  --project path/to/tsconfig.json --target path/to/project --write

Apply safely

1. Resolve the exact target root and tsconfig. Never target a broad home, workspace parent, dependency store, or node_modules directory.

2. Run the deterministic transform without --write first. Review every reported file and inspect the diff that would result.

3. Apply with --write only when the user authorized mutation:

   mise exec -- node .agents/skills/codemod/scripts/run-codemod.mjs \
     --codemod .agents/skills/codemod/codemods/YYYY-MM-DD-name \
     --project path/to/tsconfig.json \
     --target path/to/project \
     --write
   

4. Follow instructions.md for semantic sites the transform deliberately leaves unresolved. Preserve the stated ownership, ordering, error, and lifecycle invariants; stop for a real user decision instead of guessing.

5. Use AST queries to enumerate remaining old imports, identifiers, property accesses, call shapes, comments, and string literals. Change human-facing strings deliberately; do not rename protocol values, persisted data, fixture identities, generated ABI names, or artifact paths because their spelling resembles an API symbol.

6. Run every recipe verification command plus the affected package checks. Generated JavaScript, declarations, digests, and ABI files are regenerated through their owning workflow, never edited by the codemod.

For symbol renames, use the runner's renameSymbol() helper. It delegates identifiers to ts-morph's language service, scans actual comment trivia separately, and never renames string literals. A successful typecheck is necessary but does not prove semantic call sites were migrated; the recipe's behavioral postconditions remain required.

Archive rules

Recipes live under codemods/YYYY-MM-DD-slug/ and are applied in lexical date order. Once a recipe has been shared with canary users, do not rewrite its migration meaning. Add a later corrective recipe so users can apply an ordered chain. The archive is the canonical rename and call-site map; public prose links to it or is rendered from it.