CLAUDE.md

1# AI Agent Rules
2 
3When working in a specific directory, apply the rules from that directory and all parent directories up to the root.
4 
5## While working on `.`
6 
7*Source: `AGENTS.md`*
8 
9# Instructions
10 
11## General rule
12 
13-   Read the codebase - the codebase is source of truth, and you should prefer reading lots of source code over searching.
14-   Do not search web unless explicitly asked to do so. Web search does not help in general for our project.
15-   Write performant code. Always prefer performance over other things.
16-   Use `gh` CLI tool for fetching data from `github.com`.
17 
18## Code style
19 
20-   Write comments and documentations in English.
21-   Write documentation for your code.
22-   Commit your work as frequent as possible using git. Do NOT use `--no-verify` flag.
23-   Prefer multiple small files over single large file.
24 
25---
26 
27-   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.
28 
29## Testing
30 
31-   Write unit tests for your code.
32-   Prefer fixture tests over inline (`#[test]`) tests.
33-   You can do `UPDATE=1 cargo test` to get test outputs updated for fixture tests.
34-   When instructed to fix tests, do not remove or modify existing tests.
35 
36### Fixture Test Common Guide
37 
38- Add new coverage by extending existing fixture suites instead of adding ad-hoc inline tests.
39- Find the exact fixture harness before adding files with: `rg -n "#\[(testing::)?fixture\(" tests src --glob "*.rs"`.
40- Keep each suite's naming conventions (for example: input.*, output.*, exec.*, .ans).
41- 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.
42- Always rerun the same crate tests without `UPDATE` before finishing.
43 
44## Verification
45 
46-   Before finishing a task, always run this baseline locally.
47    -   `cargo fmt --all`
48    -   `cargo clippy --all --all-targets -- -D warnings`
49-   For each touched Rust crate, run crate-level verification locally.
50    -   `cargo test -p <crate>`
51-   If wasm binding packages are touched, run:
52    -   `(cd bindings/binding_core_wasm && ./scripts/test.sh)`
53    -   `(cd bindings/binding_minifier_wasm && ./scripts/test.sh)`
54    -   `(cd bindings/binding_typescript_wasm && ./scripts/test.sh)`
55    -   `(cd bindings/binding_es_ast_viewer && ./scripts/test.sh)`
56-   If node bindings or integration paths are touched, run:
57    -   `(cd packages/core && pnpm build:dev && pnpm test)`
58 
59## Compatibility rule
60 
61-   Do not use unstable, nightly only features of rustc.
62 
63 
64---
65 
66## While working on `crates/jsdoc`
67 
68*Source: `crates/jsdoc/AGENTS.md`*
69 
70### Fixture Test Addition Guide
71 
72- Preferred fixture roots in this crate: tests/fixtures.
73- Update generated fixture outputs with: UPDATE=1 cargo test -p jsdoc.
74- Verify without UPDATE before finishing: cargo test -p jsdoc.
75 
76 
77---
78 
79## While working on `crates/swc`
80 
81*Source: `crates/swc/AGENTS.md`*
82 
83### Fixture Test Addition Guide
84 
85- Preferred fixture roots in this crate: tests/fixture, tests/errors, tests/exec, tests/minify, tests/typescript, tests/vercel, tests/stacktrace, tests/babel-exec.
86- Update generated fixture outputs with: UPDATE=1 cargo test -p swc.
87- Verify without UPDATE before finishing: cargo test -p swc.
88 
89 
90---
91 
92## While working on `crates/swc_bundler`
93 
94*Source: `crates/swc_bundler/AGENTS.md`*
95 
96### Fixture Test Addition Guide
97 
98- Preferred fixture roots in this crate: tests/fixture, tests/deno-exec.
99- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_bundler.
100- Verify without UPDATE before finishing: cargo test -p swc_bundler.
101 
102 
103---
104 
105## While working on `crates/swc_core`
106 
107*Source: `crates/swc_core/AGENTS.md`*
108 
109### Fixture Test Addition Guide
110 
111- Preferred fixture roots in this crate: tests/fixture.
112- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_core.
113- Verify without UPDATE before finishing: cargo test -p swc_core.
114 
115 
116---
117 
118## While working on `crates/swc_css_codegen`
119 
120*Source: `crates/swc_css_codegen/AGENTS.md`*
121 
122### Fixture Test Addition Guide
123 
124- Preferred fixture roots in this crate: tests/fixture, tests/options, ../swc_css_parser/tests/fixture.
125- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_css_codegen.
126- Verify without UPDATE before finishing: cargo test -p swc_css_codegen.
127 
128 
129---
130 
131## While working on `crates/swc_css_compat`
132 
133*Source: `crates/swc_css_compat/AGENTS.md`*
134 
135### Fixture Test Addition Guide
136 
137- 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.
138- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_css_compat.
139- Verify without UPDATE before finishing: cargo test -p swc_css_compat.
140 
141 
142---
143 
144## While working on `crates/swc_css_lints`
145 
146*Source: `crates/swc_css_lints/AGENTS.md`*
147 
148### Fixture Test Addition Guide
149 
150- Preferred fixture roots in this crate: tests/rules/pass, tests/rules/fail.
151- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_css_lints.
152- Verify without UPDATE before finishing: cargo test -p swc_css_lints.
153 
154 
155---
156 
157## While working on `crates/swc_css_minifier`
158 
159*Source: `crates/swc_css_minifier/AGENTS.md`*
160 
161### Fixture Test Addition Guide
162 
163- Preferred fixture roots in this crate: tests/fixture.
164- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_css_minifier.
165- Verify without UPDATE before finishing: cargo test -p swc_css_minifier.
166 
167 
168---
169 
170## While working on `crates/swc_css_modules`
171 
172*Source: `crates/swc_css_modules/AGENTS.md`*
173 
174### Fixture Test Addition Guide
175 
176- Preferred fixture roots in this crate: tests/fixture, tests/with-compat.
177- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_css_modules.
178- Verify without UPDATE before finishing: cargo test -p swc_css_modules.
179 
180 
181---
182 
183## While working on `crates/swc_css_parser`
184 
185*Source: `crates/swc_css_parser/AGENTS.md`*
186 
187### Fixture Test Addition Guide
188 
189- Preferred fixture roots in this crate: tests/fixture, tests/line-comment, tests/recovery, tests/recovery-cssmodules.
190- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_css_parser.
191- Verify without UPDATE before finishing: cargo test -p swc_css_parser.
192 
193 
194---
195 
196## While working on `crates/swc_css_prefixer`
197 
198*Source: `crates/swc_css_prefixer/AGENTS.md`*
199 
200### Fixture Test Addition Guide
201 
202- Preferred fixture roots in this crate: tests/fixture.
203- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_css_prefixer.
204- Verify without UPDATE before finishing: cargo test -p swc_css_prefixer.
205 
206 
207---
208 
209## While working on `crates/swc_ecma_codegen`
210 
211*Source: `crates/swc_ecma_codegen/AGENTS.md`*
212 
213### Fixture Test Addition Guide
214 
215- Preferred fixture roots in this crate: tests/fixture, tests/str-lits, ../swc_ecma_parser/tests/test262-parser/pass.
216- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_codegen.
217- Verify without UPDATE before finishing: cargo test -p swc_ecma_codegen.
218 
219 
220---
221 
222## While working on `crates/swc_ecma_lints`
223 
224*Source: `crates/swc_ecma_lints/AGENTS.md`*
225 
226### Fixture Test Addition Guide
227 
228- Preferred fixture roots in this crate: tests/pass.
229- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_lints.
230- Verify without UPDATE before finishing: cargo test -p swc_ecma_lints.
231 
232 
233---
234 
235## While working on `crates/swc_ecma_minifier`
236 
237*Source: `crates/swc_ecma_minifier/AGENTS.md`*
238 
239### Instructions
240 
241- You can run execution tests by doing ./scripts/exec.sh to see if your changes are working.
242- If an execution test fails, you are wrong.
243- Always run execution tests after making changes.
244- You can run fixture tests by doing ./scripts/test.sh, and you can do UPDATE=1 ./scripts/test.sh to update fixtures.
245 
246### Fixture Test Addition Guide
247 
248- Preferred fixture roots in this crate: tests/fixture, tests/terser, tests/mangle, tests/pass-1, tests/pass-default, tests/full, tests/projects, benches/full.
249- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_minifier.
250- Verify without UPDATE before finishing: cargo test -p swc_ecma_minifier.
251 
252 
253---
254 
255## While working on `crates/swc_ecma_parser`
256 
257*Source: `crates/swc_ecma_parser/AGENTS.md`*
258 
259### Fixture Test Addition Guide
260 
261- Preferred fixture roots in this crate: tests/js, tests/jsx, tests/typescript, tests/typescript-errors, tests/errors, tests/comments, tests/span, tests/shifted.
262- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_parser.
263- Verify without UPDATE before finishing: cargo test -p swc_ecma_parser.
264 
265 
266---
267 
268## While working on `crates/swc_ecma_preset_env`
269 
270*Source: `crates/swc_ecma_preset_env/AGENTS.md`*
271 
272### Fixture Test Addition Guide
273 
274- Preferred fixture roots in this crate: tests/fixtures.
275- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_preset_env.
276- Verify without UPDATE before finishing: cargo test -p swc_ecma_preset_env.
277 
278 
279---
280 
281## While working on `crates/swc_ecma_transformer`
282 
283*Source: `crates/swc_ecma_transformer/AGENTS.md`*
284 
285### Instructions
286 
287-   The Transformer must implement `VisitMut` and execute the `VisitMutHooks` of its subtypes.
288-   Other types like ES20xx or transforms for specific syntax MUST NOT implement `VisitMut`.
289-   Subtypes must implement `VisitMutHook<TraverseCtx>`.
290-   Before starting work, read `$repositoryRoot/crates/swc_ecma_hooks/src/`.
291 
292 
293---
294 
295## While working on `crates/swc_ecma_transforms`
296 
297*Source: `crates/swc_ecma_transforms/AGENTS.md`*
298 
299### Fixture Test Addition Guide
300 
301- Preferred fixture roots in this crate: tests/fixture.
302- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_transforms.
303- Verify without UPDATE before finishing: cargo test -p swc_ecma_transforms.
304 
305 
306---
307 
308## While working on `crates/swc_ecma_transforms_base`
309 
310*Source: `crates/swc_ecma_transforms_base/AGENTS.md`*
311 
312### Fixture Test Addition Guide
313 
314- Preferred fixture roots in this crate: tests/resolver, tests/ts-resolver, ../swc_ecma_parser/tests.
315- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_transforms_base.
316- Verify without UPDATE before finishing: cargo test -p swc_ecma_transforms_base.
317 
318 
319---
320 
321## While working on `crates/swc_ecma_transforms_compat`
322 
323*Source: `crates/swc_ecma_transforms_compat/AGENTS.md`*
324 
325### Fixture Test Addition Guide
326 
327- 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.
328- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_transforms_compat.
329- Verify without UPDATE before finishing: cargo test -p swc_ecma_transforms_compat.
330 
331 
332---
333 
334## While working on `crates/swc_ecma_transforms_module`
335 
336*Source: `crates/swc_ecma_transforms_module/AGENTS.md`*
337 
338### Fixture Test Addition Guide
339 
340- Preferred fixture roots in this crate: tests/fixture, tests/paths.
341- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_transforms_module.
342- Verify without UPDATE before finishing: cargo test -p swc_ecma_transforms_module.
343 
344 
345---
346 
347## While working on `crates/swc_ecma_transforms_optimization`
348 
349*Source: `crates/swc_ecma_transforms_optimization/AGENTS.md`*
350 
351### Fixture Test Addition Guide
352 
353- Preferred fixture roots in this crate: tests/const-modules, tests/dce, tests/dce-jsx, tests/expr-simplifier.
354- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_transforms_optimization.
355- Verify without UPDATE before finishing: cargo test -p swc_ecma_transforms_optimization.
356 
357 
358---
359 
360## While working on `crates/swc_ecma_transforms_proposal`
361 
362*Source: `crates/swc_ecma_transforms_proposal/AGENTS.md`*
363 
364### Fixture Test Addition Guide
365 
366- Preferred fixture roots in this crate: tests/decorators, tests/explicit-resource-management.
367- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_transforms_proposal.
368- Verify without UPDATE before finishing: cargo test -p swc_ecma_transforms_proposal.
369 
370 
371---
372 
373## While working on `crates/swc_ecma_transforms_react`
374 
375*Source: `crates/swc_ecma_transforms_react/AGENTS.md`*
376 
377### Fixture Test Addition Guide
378 
379- Preferred fixture roots in this crate: tests/jsx/fixture, tests/integration/fixture, tests/script/jsx/fixture.
380- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_transforms_react.
381- Verify without UPDATE before finishing: cargo test -p swc_ecma_transforms_react.
382 
383 
384---
385 
386## While working on `crates/swc_ecma_transforms_typescript`
387 
388*Source: `crates/swc_ecma_transforms_typescript/AGENTS.md`*
389 
390### Fixture Test Addition Guide
391 
392- Preferred fixture roots in this crate: tests/fixture, ../swc_ecma_parser/tests/tsc, ../swc_ecma_parser/tests/typescript.
393- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ecma_transforms_typescript.
394- Verify without UPDATE before finishing: cargo test -p swc_ecma_transforms_typescript.
395 
396 
397---
398 
399## While working on `crates/swc_error_reporters`
400 
401*Source: `crates/swc_error_reporters/AGENTS.md`*
402 
403### Fixture Test Addition Guide
404 
405- Preferred fixture roots in this crate: tests/fixture.
406- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_error_reporters.
407- Verify without UPDATE before finishing: cargo test -p swc_error_reporters.
408 
409 
410---
411 
412## While working on `crates/swc_estree_compat`
413 
414*Source: `crates/swc_estree_compat/AGENTS.md`*
415 
416### Fixture Test Addition Guide
417 
418- Preferred fixture roots in this crate: tests/fixtures, tests/flavor/acorn/fixtures.
419- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_estree_compat.
420- Verify without UPDATE before finishing: cargo test -p swc_estree_compat.
421 
422 
423---
424 
425## While working on `crates/swc_html_codegen`
426 
427*Source: `crates/swc_html_codegen/AGENTS.md`*
428 
429### Fixture Test Addition Guide
430 
431- Preferred fixture roots in this crate: tests/fixture, tests/document_fragment, tests/options, ../swc_html_parser/tests/fixture.
432- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_html_codegen.
433- Verify without UPDATE before finishing: cargo test -p swc_html_codegen.
434 
435 
436---
437 
438## While working on `crates/swc_html_minifier`
439 
440*Source: `crates/swc_html_minifier/AGENTS.md`*
441 
442### Fixture Test Addition Guide
443 
444- Preferred fixture roots in this crate: tests/fixture, tests/document_fragment, tests/recovery.
445- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_html_minifier.
446- Verify without UPDATE before finishing: cargo test -p swc_html_minifier.
447 
448 
449---
450 
451## While working on `crates/swc_html_parser`
452 
453*Source: `crates/swc_html_parser/AGENTS.md`*
454 
455### Fixture Test Addition Guide
456 
457- Preferred fixture roots in this crate: tests/fixture, tests/recovery, tests/iframe_srcdoc, tests/html5lib-tests-fixture, tests/html5lib-tests.
458- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_html_parser.
459- Verify without UPDATE before finishing: cargo test -p swc_html_parser.
460 
461 
462---
463 
464## While working on `crates/swc_node_bundler`
465 
466*Source: `crates/swc_node_bundler/AGENTS.md`*
467 
468### Fixture Test Addition Guide
469 
470- Preferred fixture roots in this crate: tests/pass.
471- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_node_bundler.
472- Verify without UPDATE before finishing: cargo test -p swc_node_bundler.
473 
474 
475---
476 
477## While working on `crates/swc_plugin_backend_tests`
478 
479*Source: `crates/swc_plugin_backend_tests/AGENTS.md`*
480 
481### Fixture Test Addition Guide
482 
483- Preferred fixture roots in this crate: tests/fixture, ../swc_ecma_parser/tests/tsc.
484- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_plugin_backend_tests.
485- Verify without UPDATE before finishing: cargo test -p swc_plugin_backend_tests.
486 
487 
488---
489 
490## While working on `crates/swc_ts_fast_strip`
491 
492*Source: `crates/swc_ts_fast_strip/AGENTS.md`*
493 
494### Fixture Test Addition Guide
495 
496- Preferred fixture roots in this crate: tests/fixture, tests/errors, ../swc_ecma_parser/tests/tsc.
497- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_ts_fast_strip.
498- Verify without UPDATE before finishing: cargo test -p swc_ts_fast_strip.
499 
500 
501---
502 
503## While working on `crates/swc_typescript`
504 
505*Source: `crates/swc_typescript/AGENTS.md`*
506 
507### Fixture Test Addition Guide
508 
509- Preferred fixture roots in this crate: tests/**/*.ts, tests/**/*.tsx.
510- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_typescript.
511- Verify without UPDATE before finishing: cargo test -p swc_typescript.
512 
513 
514---
515 
516## While working on `crates/swc_xml_codegen`
517 
518*Source: `crates/swc_xml_codegen/AGENTS.md`*
519 
520### Fixture Test Addition Guide
521 
522- Preferred fixture roots in this crate: tests/fixture, tests/options, ../swc_xml_parser/tests/fixture, ../swc_xml_parser/tests/recovery.
523- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_xml_codegen.
524- Verify without UPDATE before finishing: cargo test -p swc_xml_codegen.
525 
526 
527---
528 
529## While working on `crates/swc_xml_parser`
530 
531*Source: `crates/swc_xml_parser/AGENTS.md`*
532 
533### Fixture Test Addition Guide
534 
535- Preferred fixture roots in this crate: tests/fixture, tests/recovery.
536- Update generated fixture outputs with: UPDATE=1 cargo test -p swc_xml_parser.
537- Verify without UPDATE before finishing: cargo test -p swc_xml_parser.
538 
539 
540---
541 
542## While working on `crates/testing_macros`
543 
544*Source: `crates/testing_macros/AGENTS.md`*
545 
546### Fixture Test Addition Guide
547 
548- Preferred fixture roots in this crate: tests/simple, tests/ignore.
549- Update generated fixture outputs with: UPDATE=1 cargo test -p testing_macros.
550- Verify without UPDATE before finishing: cargo test -p testing_macros.
551