knip Agent Skills & AI Rules

# Knip

Knip is a tool to find and fix unused dependencies, exports and files in
JavaScript and TypeScript projects.

## Project overview

- Monorepo, managed with pnpm
- Main package is core in `packages/knip` (TypeScript)
- Language Server in `packages/language-server` (JS + JSDoc for types)
- VS Code Extension in `packages/vscode-knip` (JS + JSDoc for types)
- [Documentation][1] content in `packages/docs` (Astro + MD/MDX)
- Tracked `.agents` guides live in the checkout; there might be shared lessons and tasks in the workspace's `.agents`.

## Code style

- Performance is key, both high level (design) and low level (impl).
- Avoid redundant code and abstractions; avoid unnecessary complexity and nesting.
- Concise one-liners are fine, but prioritize clarity over cleverness.
- Don't add comments to code, unless explicitly asked for.
- Prefer AST-based tools and codemods (jscodeshift) over manual or regex-based refactors — except for tiny edits.
- JavaScript
  - Prefer plain `for..in/of` loops over iterator methods like `map`/`reduce`.
- TypeScript
  - Avoid `any` and type casting (`as`).
  - Avoid runtime overhead just to get the types right.
- Lint and check formatting from root: `pnpm run ci`; format with `pnpm fmt`
- Format Markdown/MDX with `pnpm remark` in `packages/docs` (auto-numbers link refs, validates links)

## Domain Knowledge

- Unused file → unused exports/dependencies is a chain, not a bug
- Non-JS/TS files (.css, .mdx, .vue) enter the graph via (usually plugin-registered) compilers (`registerCompilers`)
- Library-specific AST patterns are caught by plugin-registered visitors (`registerVisitors`)
- Use `--performance` or `--performance-fn [name]` to profile (→ [timerify][2])
- If creating, modifying, or reviewing a plugin, read [PLUGINS.md][3] first.
- If modifying core module graph, AST traversal, or CLI sequence, read [MODULE-GRAPH.md][4] first.
- For issues re. exported identifiers (following refs, shadowing, `ignoreExportsUsedInFile`), see [EXPORTS.md][5].
- Before any significant performance tuning, consult [PERFORMANCE.md][6].
- When modifying or reviewing built-in compilers, read [COMPILERS.md][10].
- For test/fixture structure, conventions, and where a new test goes, see [TESTS.md][7].

## Issues and Pull Requests

- Use `gh` for PR metadata, diffs, comments, and checks. Reuse retrieved evidence; browse upstream documentation separately.
- When given a bug report, first confirm the behavior is actually wrong. Reproduce, then check if the reported behavior is correct-by-design before writing any fix.
- Find repositories/CodeSandbox/StackBlitz source files and local fixtures to actually reproduce the issue at hand.
- To fetch a stackblitz.com reproduction: `pnpx stackblitz-zip https://stackblitz.com/edit/{name} {filename}.zip`
- For a fix, revert the source change and confirm the new test fails for the reported reason.
- For a new plugin or a change in how a tool finds files, verify against the tool's source, not only its docs, and run Knip on the tool's examples or starters when available.
- Follow the [AI contribution policy][11]: before opening an issue or PR, make sure the person you work for understands and stands behind it. Keep descriptions concise.

## Run & Debug

Important: debug, don't guess.

Run the CLI directly using `node` or `bun`. This document shows `knip` in
commands for consistency. Replace it with `node (path/to/)src/cli.ts` or
`bun (path/to/)src/cli.ts` and keep using what works.

- Run `knip` directly in a fixture or temp directory (over creating test scripts that import the `main` function).
- Knip requires `package.json` in root dir.
- Enable [debug & helpers][8] with `--debug` (not `DEBUG=`). Warning: noisy.
- Use [trace][9] to debug
  - exported identifiers (`knip --trace-export [name] --trace-file [file]`)
  - external dependencies (`knip --trace-dependency [name] --workspace [dir]`)

## Test

Prefer TDD: add or update tests (and fixtures) before implementing.

Prefer `bun` over `node` for speed. Don't run all tests at once (slow & noisy).
Start out with running the relevant test(s) first:

```sh
cd packages/knip
bun test test/util/get-inputs-from-scripts.test.ts
node --test test/commonjs.test.ts
```

Run smoke tests with Bun:

```sh
cd packages/knip
pnpm test --runtime bun --smoke
```

Run smoke tests with Node.js:

```sh
cd packages/knip
node --test test/commonjs.test.ts
pnpm test --runtime node --smoke
```

Build core package and run all tests only if there are changes in auto-fix,
formatting and reporter related functionality:

```sh
cd packages/knip
pnpm build
pnpm test
```

See [TESTS.md][7] for test and fixture conventions and placements.

## Build

To type-check `knip` with `tsc`:

```sh
cd packages/knip
pnpm build
```

[1]: https://knip.dev
[2]: ./packages/knip/src/util/Performance.ts
[3]: ./.agents/PLUGINS.md
[4]: ./.agents/MODULE-GRAPH.md
[5]: ./.agents/EXPORTS.md
[6]: ./.agents/PERFORMANCE.md
[7]: ./.agents/TESTS.md
[8]: ./packages/knip/src/util/debug.ts
[9]: ./packages/docs/src/content/docs/guides/troubleshooting.md#trace
[10]: ./.agents/COMPILERS.md
[11]: ./AI_POLICY.md