swc

# AI Agent Rules

When working in a specific directory, apply the rules from that directory and all parent directories up to the root.

## While working on `.`

*Source: `AGENTS.md`*

# Instructions

## General rule

-   Read the codebase - the codebase is source of truth, and you should prefer reading lots of source code over searching.
-   Do not search web unless explicitly asked to do so. Web search does not help in general for our project.
-   Write performant code. Always prefer performance over other things.
-   Use `gh` CLI tool for fetching data from `github.com`.

## Code style

-   Write comments and documentations in English.
-   Write documentation for your code.
-   Commit your work as frequent as possible using git. Do NOT use `--no-verify` flag.
-   Prefer multiple small files over single large file.

---

-   When creating Atom instances, it's better to use `Cow<str>` or `&str` instead of `String`. Note that `&str` is better than `Cow<str>` here.

## Testing

-   Write unit tests for your code.
-   Prefer fixture tests over inline (`#[test]`) tests.
-   You can do `UPDATE=1 cargo test` to get test outputs updated for fixture tests.
-   When instructed to fix tests, do not remove or modify existing tests.

### Fixture Test Common Guide

- Add new coverage by extending existing fixture suites instead of adding ad-hoc inline tests.
- Find the exact fixture harness before adding files with: `rg -n "#\[(testing::)?fixture\(" tests src --glob "*.rs"`.
- Keep each suite's naming conventions (for example: input.*, output.*, exec.*, .ans).
- For snapshot-style tests, update expected outputs with `UPDATE=1 cargo test -p ...` using the exact crate command documented in each crate's AGENTS.md.
- Always rerun the same crate tests without `UPDATE` before finishing.

## Verification

-   Before finishing a task, always run this baseline locally.
    -   `cargo fmt --all`
    -   `cargo clippy --all --all-targets -- -D warnings`
-   For each touched Rust crate, run crate-level verification locally.
    -   `cargo test -p <crate>`
-   If wasm binding packages are touched, run:
    -   `(cd bindings/binding_core_wasm && ./scripts/test.sh)`
    -   `(cd bindings/binding_minifier_wasm && ./scripts/test.sh)`
    -   `(cd bindings/binding_typescript_wasm && ./scripts/test.sh)`
    -   `(cd bindings/binding_es_ast_viewer && ./scripts/test.sh)`
-   If node bindings or integration paths are touched, run:
    -   `(cd packages/core && pnpm build:dev && pnpm test)`

## Compatibility rule

-   Do not use unstable, nightly only features of rustc.


---

## While working on `crates/jsdoc`

*Source: `crates/jsdoc/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/fixtures.
- Update generated fixture outputs with: UPDATE=1 cargo test -p jsdoc.
- Verify without UPDATE before finishing: cargo test -p jsdoc.


---

## While working on `crates/swc`

*Source: `crates/swc/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/fixture, tests/errors, tests/exec, tests/minify, tests/typescript, tests/vercel, tests/stacktrace, tests/babel-exec.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc.
- Verify without UPDATE before finishing: cargo test -p swc.


---

## While working on `crates/swc_bundler`

*Source: `crates/swc_bundler/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/fixture, tests/deno-exec.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_bundler.
- Verify without UPDATE before finishing: cargo test -p swc_bundler.


---

## While working on `crates/swc_core`

*Source: `crates/swc_core/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/fixture.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_core.
- Verify without UPDATE before finishing: cargo test -p swc_core.


---

## While working on `crates/swc_css_codegen`

*Source: `crates/swc_css_codegen/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/fixture, tests/options, ../swc_css_parser/tests/fixture.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_css_codegen.
- Verify without UPDATE before finishing: cargo test -p swc_css_codegen.


---

## While working on `crates/swc_css_compat`

*Source: `crates/swc_css_compat/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/nesting, tests/custom-media-query, tests/media-query-ranges, tests/color-hex-alpha, tests/color-legacy, tests/selector-not, tests/color-hwb, tests/all.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_css_compat.
- Verify without UPDATE before finishing: cargo test -p swc_css_compat.


---

## While working on `crates/swc_css_lints`

*Source: `crates/swc_css_lints/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/rules/pass, tests/rules/fail.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_css_lints.
- Verify without UPDATE before finishing: cargo test -p swc_css_lints.


---

## While working on `crates/swc_css_minifier`

*Source: `crates/swc_css_minifier/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/fixture.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_css_minifier.
- Verify without UPDATE before finishing: cargo test -p swc_css_minifier.


---

## While working on `crates/swc_css_modules`

*Source: `crates/swc_css_modules/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/fixture, tests/with-compat.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_css_modules.
- Verify without UPDATE before finishing: cargo test -p swc_css_modules.


---

## While working on `crates/swc_css_parser`

*Source: `crates/swc_css_parser/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/fixture, tests/line-comment, tests/recovery, tests/recovery-cssmodules.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_css_parser.
- Verify without UPDATE before finishing: cargo test -p swc_css_parser.


---

## While working on `crates/swc_css_prefixer`

*Source: `crates/swc_css_prefixer/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/fixture.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_css_prefixer.
- Verify without UPDATE before finishing: cargo test -p swc_css_prefixer.


---

## While working on `crates/swc_ecma_codegen`

*Source: `crates/swc_ecma_codegen/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/fixture, tests/str-lits, ../swc_ecma_parser/tests/test262-parser/pass.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_codegen.
- Verify without UPDATE before finishing: cargo test -p swc_ecma_codegen.


---

## While working on `crates/swc_ecma_lints`

*Source: `crates/swc_ecma_lints/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/pass.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_lints.
- Verify without UPDATE before finishing: cargo test -p swc_ecma_lints.


---

## While working on `crates/swc_ecma_minifier`

*Source: `crates/swc_ecma_minifier/AGENTS.md`*

### Instructions

- You can run execution tests by doing ./scripts/exec.sh to see if your changes are working.
- If an execution test fails, you are wrong.
- Always run execution tests after making changes.
- You can run fixture tests by doing ./scripts/test.sh, and you can do UPDATE=1 ./scripts/test.sh to update fixtures.

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/fixture, tests/terser, tests/mangle, tests/pass-1, tests/pass-default, tests/full, tests/projects, benches/full.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_minifier.
- Verify without UPDATE before finishing: cargo test -p swc_ecma_minifier.


---

## While working on `crates/swc_ecma_parser`

*Source: `crates/swc_ecma_parser/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/js, tests/jsx, tests/typescript, tests/typescript-errors, tests/errors, tests/comments, tests/span, tests/shifted.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_parser.
- Verify without UPDATE before finishing: cargo test -p swc_ecma_parser.


---

## While working on `crates/swc_ecma_preset_env`

*Source: `crates/swc_ecma_preset_env/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/fixtures.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_preset_env.
- Verify without UPDATE before finishing: cargo test -p swc_ecma_preset_env.


---

## While working on `crates/swc_ecma_transformer`

*Source: `crates/swc_ecma_transformer/AGENTS.md`*

### Instructions

-   The Transformer must implement `VisitMut` and execute the `VisitMutHooks` of its subtypes.
-   Other types like ES20xx or transforms for specific syntax MUST NOT implement `VisitMut`.
-   Subtypes must implement `VisitMutHook<TraverseCtx>`.
-   Before starting work, read `$repositoryRoot/crates/swc_ecma_hooks/src/`.


---

## While working on `crates/swc_ecma_transforms`

*Source: `crates/swc_ecma_transforms/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/fixture.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_transforms.
- Verify without UPDATE before finishing: cargo test -p swc_ecma_transforms.


---

## While working on `crates/swc_ecma_transforms_base`

*Source: `crates/swc_ecma_transforms_base/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/resolver, tests/ts-resolver, ../swc_ecma_parser/tests.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_transforms_base.
- Verify without UPDATE before finishing: cargo test -p swc_ecma_transforms_base.


---

## While working on `crates/swc_ecma_transforms_compat`

*Source: `crates/swc_ecma_transforms_compat/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/arrow, tests/async-to-generator, tests/block-scoping, tests/class-properties, tests/class_fields_use_set, tests/classes, tests/destructuring, tests/for-of, tests/new-target, tests/object-rest-spread, tests/optional-chaining, tests/optional-chaining-loose, tests/parameters, tests/private-in-object, tests/shorthand_properties, tests/static-blocks.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_transforms_compat.
- Verify without UPDATE before finishing: cargo test -p swc_ecma_transforms_compat.


---

## While working on `crates/swc_ecma_transforms_module`

*Source: `crates/swc_ecma_transforms_module/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/fixture, tests/paths.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_transforms_module.
- Verify without UPDATE before finishing: cargo test -p swc_ecma_transforms_module.


---

## While working on `crates/swc_ecma_transforms_optimization`

*Source: `crates/swc_ecma_transforms_optimization/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/const-modules, tests/dce, tests/dce-jsx, tests/expr-simplifier.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_transforms_optimization.
- Verify without UPDATE before finishing: cargo test -p swc_ecma_transforms_optimization.


---

## While working on `crates/swc_ecma_transforms_proposal`

*Source: `crates/swc_ecma_transforms_proposal/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/decorators, tests/explicit-resource-management.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_transforms_proposal.
- Verify without UPDATE before finishing: cargo test -p swc_ecma_transforms_proposal.


---

## While working on `crates/swc_ecma_transforms_react`

*Source: `crates/swc_ecma_transforms_react/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/jsx/fixture, tests/integration/fixture, tests/script/jsx/fixture.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_transforms_react.
- Verify without UPDATE before finishing: cargo test -p swc_ecma_transforms_react.


---

## While working on `crates/swc_ecma_transforms_typescript`

*Source: `crates/swc_ecma_transforms_typescript/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/fixture, ../swc_ecma_parser/tests/tsc, ../swc_ecma_parser/tests/typescript.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_transforms_typescript.
- Verify without UPDATE before finishing: cargo test -p swc_ecma_transforms_typescript.


---

## While working on `crates/swc_error_reporters`

*Source: `crates/swc_error_reporters/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/fixture.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_error_reporters.
- Verify without UPDATE before finishing: cargo test -p swc_error_reporters.


---

## While working on `crates/swc_estree_compat`

*Source: `crates/swc_estree_compat/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/fixtures, tests/flavor/acorn/fixtures.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_estree_compat.
- Verify without UPDATE before finishing: cargo test -p swc_estree_compat.


---

## While working on `crates/swc_html_codegen`

*Source: `crates/swc_html_codegen/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/fixture, tests/document_fragment, tests/options, ../swc_html_parser/tests/fixture.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_html_codegen.
- Verify without UPDATE before finishing: cargo test -p swc_html_codegen.


---

## While working on `crates/swc_html_minifier`

*Source: `crates/swc_html_minifier/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/fixture, tests/document_fragment, tests/recovery.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_html_minifier.
- Verify without UPDATE before finishing: cargo test -p swc_html_minifier.


---

## While working on `crates/swc_html_parser`

*Source: `crates/swc_html_parser/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/fixture, tests/recovery, tests/iframe_srcdoc, tests/html5lib-tests-fixture, tests/html5lib-tests.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_html_parser.
- Verify without UPDATE before finishing: cargo test -p swc_html_parser.


---

## While working on `crates/swc_node_bundler`

*Source: `crates/swc_node_bundler/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/pass.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_node_bundler.
- Verify without UPDATE before finishing: cargo test -p swc_node_bundler.


---

## While working on `crates/swc_plugin_backend_tests`

*Source: `crates/swc_plugin_backend_tests/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/fixture, ../swc_ecma_parser/tests/tsc.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_plugin_backend_tests.
- Verify without UPDATE before finishing: cargo test -p swc_plugin_backend_tests.


---

## While working on `crates/swc_ts_fast_strip`

*Source: `crates/swc_ts_fast_strip/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/fixture, tests/errors, ../swc_ecma_parser/tests/tsc.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ts_fast_strip.
- Verify without UPDATE before finishing: cargo test -p swc_ts_fast_strip.


---

## While working on `crates/swc_typescript`

*Source: `crates/swc_typescript/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/**/*.ts, tests/**/*.tsx.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_typescript.
- Verify without UPDATE before finishing: cargo test -p swc_typescript.


---

## While working on `crates/swc_xml_codegen`

*Source: `crates/swc_xml_codegen/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/fixture, tests/options, ../swc_xml_parser/tests/fixture, ../swc_xml_parser/tests/recovery.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_xml_codegen.
- Verify without UPDATE before finishing: cargo test -p swc_xml_codegen.


---

## While working on `crates/swc_xml_parser`

*Source: `crates/swc_xml_parser/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/fixture, tests/recovery.
- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_xml_parser.
- Verify without UPDATE before finishing: cargo test -p swc_xml_parser.


---

## While working on `crates/testing_macros`

*Source: `crates/testing_macros/AGENTS.md`*

### Fixture Test Addition Guide

- Preferred fixture roots in this crate: tests/simple, tests/ignore.
- Update generated fixture outputs with: UPDATE=1 cargo test -p testing_macros.
- Verify without UPDATE before finishing: cargo test -p testing_macros.

More agent context in swc-project/swc

4 other files this repository gives its agents.