feat: add js/ts family support

README.md

@@ -4,8 +4,8 @@
 
 - untracked files included in default stats
 - language filtering with `--lang`
-- Rust-only, non-test-only stats by default, with `--test`, `--no-test`, and `--no-test-filter`
-- test-aware filtering for Rust and Python
+- non-test-only stats by default across all supported languages, with `--test`, `--no-test`, and `--no-test-filter`
+- test-aware filtering for Rust, Python, and JS/TS families
 - single-commit and revision-range support
 
 This repository also ships `rust-test-audit`, a companion CLI for auditing Rust source trees
@@ -75,22 +75,23 @@ git diff-stat --last
 git diff-stat --last --no-test-filter
 git diff-stat HEAD~1..HEAD --lang py --no-test-filter
 git diff-stat --lang py --test
+git diff-stat --lang tsx --test
 git diff-stat --test
 ```
 
 ## Usage
 
 ```bash
-git diff-stat [<rev> | <rev1> <rev2> | <rev-range>] [--lang rs,py,js] [--test | --no-test | --no-test-filter]
+git diff-stat [<rev> | <rev1> <rev2> | <rev-range>] [--lang rs,py,js,ts,jsx,tsx,cjs,mjs] [--test | --no-test | --no-test-filter]
 ```
 
 Defaults:
 
-- `--lang` defaults to `rs,py`
+- `--lang` defaults to all supported languages: `rs,py,js,ts,jsx,tsx,cjs,mjs`
 - test filtering defaults to `--no-test`
 - output always begins with a header line describing the comparison scope, languages, and test scope
 
-That means plain `git diff-stat` already reports Rust and Python non-test changes together.
+That means plain `git diff-stat` already reports non-test changes across all currently supported languages.
 
 ## Rust Test Audit
 
@@ -131,8 +132,9 @@ test regions cross configurable density thresholds.
 - `--lang` currently uses file extensions.
 - `--test` and `--no-test` treat Rust files under `tests/` and Rust files imported by `#[cfg(test)]` module declarations as whole-file test code. Other Rust files still use code-region splitting for `#[cfg(test)]` modules and test-annotated functions such as `#[test]` and `#[tokio::test]`.
 - `--test` and `--no-test` treat Python files under `tests/`, `test_*.py`, `*_test.py`, and `conftest.py` as whole-file test code. Other Python files split test regions using `def test_*` and `class Test*`.
-- `--no-test-filter` disables Rust and Python test splitting entirely and reports full-file stats for the selected languages.
-- because `--lang` defaults to `rs,py`, use `--lang rs` or `--lang py` when you want a narrower language set.
+- `--test` and `--no-test` treat JS/TS family files under `__tests__/`, `e2e/`, `cypress/`, and `playwright/`, plus files matching `*.test.*`, `*.spec.*`, and `*.cy.*`, as whole-file test code.
+- `--no-test-filter` disables Rust and Python region splitting and reports full-file stats for the selected languages.
+- `--lang` defaults to all supported languages, so use `--lang rs`, `--lang py`, or `--lang tsx` when you want a narrower language set.
 - `--last` is sugar for the patch introduced by `HEAD`, equivalent to `HEAD^!`.
-- rendered output starts with a Chinese description line such as `未提交的 rs,py 文件中，非测试代码统计如下：`.
+- rendered output starts with a Chinese description line such as `未提交的 rs,py,js,ts,jsx,tsx,cjs,mjs 文件中，非测试代码统计如下：`.
 - Output is intentionally close to `git diff --stat`, but not byte-for-byte identical.

docs/plans/2026-03-21-js-ts-family-support-design.md

@@ -0,0 +1,274 @@
+# JS/TS Family Language Support Design
+
+**Context**
+
+`git-diff-stat` currently supports Rust and Python as first-class test-aware languages. The language layer in [`src/lang/mod.rs`](../../src/lang/mod.rs) still has two structural limits:
+
+- the default `--lang` behavior is represented as a hard-coded CLI string instead of "all supported languages"
+- JS and TS are only partially recognized as file extensions, and they do not participate in `--test` or `--no-test`
+
+The next goal is broader frontend language coverage:
+
+- support `js`, `ts`, `jsx`, `tsx`, `cjs`, and `mjs`
+- treat unit tests and e2e tests as test code
+- change default `--lang` semantics from a fixed subset to "all supported languages"
+
+The user explicitly approved a narrow first version for JS/TS test semantics:
+
+- whole-file test classification only
+- no file-internal `describe` / `it` / `test` region splitting
+
+**Goal**
+
+Add first-class JS/TS family support with test-aware filtering, while making default language selection come from the language registry rather than from a duplicated string literal in the CLI layer.
+
+The result should make future language additions easier, not harder.
+
+**Approaches**
+
+1. Minimal patching
+   - Add more extensions directly in [`src/lang/mod.rs`](../../src/lang/mod.rs)
+   - Change the CLI default string from `rs,py` to a longer comma-separated list
+   - Add ad hoc JS/TS branches in [`src/test_filter.rs`](../../src/test_filter.rs)
+   - Rejected because the default language list would still be duplicated across language detection, CLI help, README, and tests.
+
+2. Registry-driven defaults with lightweight JS/TS backend support
+   - Introduce a single source of truth for supported languages
+   - Derive default `--lang` behavior from that registry
+   - Add a JS/TS backend that performs whole-file test classification only
+   - Recommended.
+
+3. Full backend capability framework
+   - Build a more generic trait/capability model for path matching, whole-file classification, region splitting, aliasing, and default inclusion
+   - Technically clean, but over-designed for the current repository size
+   - Rejected for now.
+
+**Decision**
+
+Use registry-driven defaults plus a lightweight JS/TS backend.
+
+This keeps the current Rust/Python design direction, but tightens two pieces that are now becoming important:
+
+- "supported languages" must live in one place
+- test-aware orchestration must support languages that only provide whole-file test classification
+
+**Default Language Semantics**
+
+`--lang` should no longer default to a hard-coded subset such as `rs,py`.
+
+Instead:
+
+- if the user passes `--lang`, respect exactly that explicit set
+- if the user omits `--lang`, treat it as "all supported languages"
+
+For the current repository state after this change, "all supported languages" means:
+
+- `rs`
+- `py`
+- `js`
+- `ts`
+- `jsx`
+- `tsx`
+- `cjs`
+- `mjs`
+
+This should be surfaced consistently in:
+
+- CLI parsing
+- output headers
+- help text examples
+- README defaults
+- tests
+
+The critical rule is that the support list should be declared once in the language layer and reused everywhere else.
+
+**Proposed Structure**
+
+- `src/lang/mod.rs`
+  - registry of supported language tokens
+  - parsing for explicit `--lang` values
+  - default-language expansion when `--lang` is omitted
+  - path-to-language detection
+- `src/lang/rust.rs`
+  - existing Rust support
+  - whole-file test classification plus region splitting
+- `src/lang/python.rs`
+  - existing Python support
+  - whole-file test classification plus region splitting
+- `src/lang/javascript.rs`
+  - JS/TS family path matching
+  - whole-file test classification only
+- `src/test_filter.rs`
+  - shared orchestration across selected languages
+  - support for backends that only classify whole-file test paths
+
+This is still a moderate refactor, not a rewrite.
+
+**Language Registry Shape**
+
+The registry only needs to answer a few central questions:
+
+- which language tokens are supported?
+- which token matches a given path?
+- what is the default language set when `--lang` is omitted?
+
+One practical model is:
+
+- `supported_langs() -> &'static [&'static str]`
+- `default_langs() -> &'static [&'static str]`
+- `parse_langs(value: Option<&str>) -> Vec<&str>`
+- `detect_language(path: &str) -> Option<&'static str>`
+
+For now, `default_langs()` can simply return the same list as `supported_langs()`.
+
+This avoids duplicating the support list in [`src/cli.rs`](../../src/cli.rs) and [`README.md`](../../README.md).
+
+**JS/TS Family Matching**
+
+The new frontend backend should recognize these extensions directly:
+
+- `.js`
+- `.ts`
+- `.jsx`
+- `.tsx`
+- `.cjs`
+- `.mjs`
+
+Each extension should map to its own `--lang` token. This keeps filtering precise:
+
+- `--lang js` should not automatically include `ts`
+- `--lang tsx` should only include `.tsx`
+- omitting `--lang` includes all of them
+
+This is a better fit for current CLI semantics than collapsing everything into a single `web` alias.
+
+**JS/TS Test Semantics**
+
+The approved first version is whole-file classification only.
+
+Treat these as test files:
+
+- any file under a `__tests__/` path component
+- filenames matching `*.test.<ext>`
+- filenames matching `*.spec.<ext>`
+- any file under an `e2e/` path component
+- any file under a `cypress/` path component
+- any file under a `playwright/` path component
+- filenames matching `*.cy.<ext>`
+
+Where `<ext>` is one of:
+
+- `js`
+- `ts`
+- `jsx`
+- `tsx`
+- `cjs`
+- `mjs`
+
+These rules intentionally cover both unit and e2e test conventions.
+
+**Out of Scope**
+
+Not in scope for the first JS/TS version:
+
+- file-internal test block detection using `describe`, `it`, `test`, or `suite`
+- `vitest` inline test detection such as `import.meta.vitest`
+- framework-specific config discovery from Jest, Vitest, Playwright, Cypress, or custom tooling
+- special handling for snapshot files
+
+This is intentional. Most real-world JS/TS repositories still place tests in dedicated files or directories, so whole-file classification captures the highest-value cases with low false-positive risk.
+
+**Test-Filter Orchestration**
+
+The shared builder in [`src/test_filter.rs`](../../src/test_filter.rs) currently assumes that selected languages either:
+
+- have whole-file test paths and region splitting, or
+- are ignored entirely
+
+JS/TS adds a third useful case:
+
+- whole-file test classification only
+
+The orchestration should therefore support:
+
+1. languages with whole-file and region split support
+2. languages with whole-file-only support
+
+For JS/TS family files:
+
+- if a file matches a whole-file test rule, count it as test code
+- otherwise, count the full file diff as non-test code
+
+That preserves correct semantics for `--test`, `--no-test`, and `--no-test-filter` without introducing AST parsing.
+
+**Source Loading Strategy**
+
+This addition makes source-loading efficiency more important.
+
+Rust still needs source contents for path-imported `#[cfg(test)]` module detection. Python and JS/TS whole-file classification are path-driven. The design should avoid eager content reads for languages that only need paths.
+
+That means the shared builder should distinguish between:
+
+- path-only whole-file classification
+- source-assisted whole-file classification
+- region splitting
+
+Even if the implementation stays simple, it should at least avoid bulk-reading JS/TS files just to classify them by filename or directory name.
+
+**Data Flow**
+
+After the refactor, runtime behavior should look like this:
+
+1. Parse CLI.
+2. Resolve revision selection.
+3. Parse explicit `--lang`, or expand to all supported languages if omitted.
+4. Filter `FileChange` values to the selected languages.
+5. If `--no-test-filter`, render full-file stats directly.
+6. Otherwise:
+   - compute whole-file test paths for each selected language backend
+   - use region splitting only for languages that implement it
+   - treat JS/TS non-test files as full-file non-test diffs
+7. Render the existing header with the updated language scope.
+
+The biggest behavioral change is that plain `git diff-stat` now means "all supported languages" instead of "Rust and Python only".
+
+**Testing Strategy**
+
+Add coverage at three levels:
+
+1. Registry and extension tests
+   - supported language parsing
+   - default language expansion
+   - path detection for `js`, `ts`, `jsx`, `tsx`, `cjs`, `mjs`
+2. JS/TS test classification unit tests
+   - `__tests__/`
+   - `*.test.*`
+   - `*.spec.*`
+   - `e2e/`
+   - `cypress/`
+   - `playwright/`
+   - `*.cy.*`
+3. CLI smoke tests
+   - default run includes supported frontend files
+   - default `--no-test` excludes JS/TS unit and e2e test files
+   - `--test` includes those files
+   - `--no-test-filter` restores full-file counting
+   - explicit `--lang tsx` or `--lang cjs` behaves narrowly
+
+The smoke suite should also prove that mixed repositories still combine Rust, Python, and JS/TS families correctly.
+
+**Risks**
+
+- If default-language logic remains duplicated, future additions will drift again between CLI, README, and actual behavior.
+- If JS/TS whole-file rules are too broad, application code under directories like `tests-data/` or `playwright.config.ts` could be misclassified; the patterns should stay intentionally narrow and component-based.
+- If the builder eagerly reads all JS/TS sources, repositories with many frontend assets could take an unnecessary performance hit.
+
+**Outcome**
+
+After this change:
+
+1. plain `git diff-stat` covers all supported languages
+2. JS/TS family files participate in `--test` and `--no-test`
+3. test-aware orchestration no longer assumes every language must support region splitting
+
+That is enough structure to add more path-driven languages later without reworking the CLI defaults again.