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perf(fmt): avoid absolute path joins in gitignore matching #245

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Merged
chenjiahan merged 1 commit into from
Aug 8, 2026
Merged

perf(fmt): avoid absolute path joins in gitignore matching #245

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18 changes: 10 additions & 8 deletions packages/rstack/src/fmt/discoverPaths.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -153,7 +153,8 @@ class GitIgnoreMatcher {
// Ignore files may disappear or become unreadable during traversal.
const loading = readFile(path.join(directoryPath, '.gitignore'), 'utf8')
.then((content) => {
this.#matchers.set(directoryPath, ignore().add(content));
const relativePath = toPosixPath(this.#resolveRelativePath(directoryPath));
this.#matchers.set(relativePath, ignore().add(content));
})
.catch(() => undefined);

Expand All @@ -179,18 +180,19 @@ class GitIgnoreMatcher {
}

#matches(relativePath: string, isDirectory: boolean): boolean {
const pathFromRoot = toPosixPath(relativePath);

// Most repositories only use a root `.gitignore`. Avoid checking every path
// segment when no nested matcher can override its result.
const rootMatcher = this.#matchers.size === 1 ? this.#matchers.get(this.#rootPath) : undefined;
const rootMatcher = this.#matchers.size === 1 ? this.#matchers.get('') : undefined;
if (rootMatcher) {
// `ignore` expects POSIX separators and uses a trailing slash to distinguish directories.
const pathFromMatcher = toPosixPath(relativePath);
return rootMatcher.test(isDirectory ? `${pathFromMatcher}/` : pathFromMatcher).ignored;
return rootMatcher.test(isDirectory ? `${pathFromRoot}/` : pathFromRoot).ignored;
}

const segments = relativePath.split(path.sep);
let directoryPath = this.#rootPath;
let pathFromMatcher = segments.join('/');
const segments = pathFromRoot.split('/');
let directoryPath = '';
let pathFromMatcher = pathFromRoot;
let ignored = false;

for (const segment of segments) {
Expand All @@ -205,7 +207,7 @@ class GitIgnoreMatcher {
}
}

directoryPath = path.join(directoryPath, segment);
directoryPath = directoryPath ? `${directoryPath}/${segment}` : segment;
pathFromMatcher = pathFromMatcher.slice(segment.length + 1);
}

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17 changes: 17 additions & 0 deletions packages/rstack/tests/fmt/discoverPaths.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -122,6 +122,23 @@ test('applies nested gitignore rules with child negation', async () => {
});
});

test('applies a nested gitignore without a root matcher', async () => {
await withTempProject(async (rootPath) => {
writeProjectFile(rootPath, 'src/.gitignore', '*.js\n');
writeProjectFile(rootPath, 'src/drop.js');
writeProjectFile(rootPath, 'src/keep.ts');
writeProjectFile(rootPath, 'root.js');

const files = await discoverFmtPaths({ cwd: rootPath });

expect(relativePaths(rootPath, files)).toEqual([
'root.js',
path.join('src', '.gitignore'),
path.join('src', 'keep.ts'),
]);
});
});

test('lets explicit files bypass gitignore', async () => {
await withTempProject(async (rootPath) => {
writeProjectFile(rootPath, '.gitignore', '/generated/\n');
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