feat(fmt): enable parallel formatting

packages/rstack/THIRD_PARTY_NOTICES.md

@@ -171,6 +171,63 @@ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
 
+## isoconcurrency
+
+This package includes bundled code from
+[isoconcurrency](https://github.com/fabiospampinato/isoconcurrency).
+
+License: MIT
+
+The MIT License (MIT)
+
+Copyright (c) 2025-present Fabio Spampinato
+
+Permission is hereby granted, free of charge, to any person obtaining a
+copy of this software and associated documentation files (the "Software"),
+to deal in the Software without restriction, including without limitation
+the rights to use, copy, modify, merge, publish, distribute, sublicense,
+and/or sell copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
+
+## isotimer
+
+This package includes bundled code from [isotimer](https://github.com/fabiospampinato/isotimer).
+
+License: MIT
+
+The MIT License (MIT)
+
+Copyright (c) 2025-present Fabio Spampinato
+
+Permission is hereby granted, free of charge, to any person obtaining a
+copy of this software and associated documentation files (the "Software"),
+to deal in the Software without restriction, including without limitation
+the rights to use, copy, modify, merge, publish, distribute, sublicense,
+and/or sell copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
+
 ## micromatch
 
 This package includes bundled code from [micromatch](https://github.com/micromatch/micromatch).
@@ -283,6 +340,35 @@ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 
+## promise-make-naked
+
+This package includes bundled code from
+[promise-make-naked](https://github.com/fabiospampinato/promise-make-naked).
+
+License: MIT
+
+The MIT License (MIT)
+
+Copyright (c) 2021-present Fabio Spampinato
+
+Permission is hereby granted, free of charge, to any person obtaining a
+copy of this software and associated documentation files (the "Software"),
+to deal in the Software without restriction, including without limitation
+the rights to use, copy, modify, merge, publish, distribute, sublicense,
+and/or sell copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
+
 ## tinyexec
 
 This package includes bundled code from [tinyexec](https://github.com/tinylibs/tinyexec).
@@ -338,3 +424,60 @@ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 DEALINGS IN THE SOFTWARE.
+
+## webworker-shim
+
+This package includes bundled code from
+[webworker-shim](https://github.com/fabiospampinato/webworker-shim).
+
+License: MIT
+
+The MIT License (MIT)
+
+Copyright (c) 2022-present Fabio Spampinato
+
+Permission is hereby granted, free of charge, to any person obtaining a
+copy of this software and associated documentation files (the "Software"),
+to deal in the Software without restriction, including without limitation
+the rights to use, copy, modify, merge, publish, distribute, sublicense,
+and/or sell copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
+
+## worktank
+
+This package includes bundled code from [worktank](https://github.com/fabiospampinato/worktank).
+
+License: MIT
+
+The MIT License (MIT)
+
+Copyright (c) 2021-present Fabio Spampinato
+
+Permission is hereby granted, free of charge, to any person obtaining a
+copy of this software and associated documentation files (the "Software"),
+to deal in the Software without restriction, including without limitation
+the rights to use, copy, modify, merge, publish, distribute, sublicense,
+and/or sell copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.

packages/rstack/package.json

@@ -75,7 +75,8 @@
     "micromatch": "catalog:",
     "rslog": "catalog:",
     "tiny-readdir": "catalog:",
-    "typescript": "catalog:"
+    "typescript": "catalog:",
+    "worktank": "catalog:"
   },
   "peerDependencies": {
     "@rspress/core": "^2.0.17"

packages/rstack/src/fmt/cli.ts

@@ -10,6 +10,7 @@ import type { FmtMode, FmtRunResult } from './types.ts';
 interface ParsedFmtCLIArgs {
   mode: FmtMode;
   patterns: string[];
+  parallel: boolean;
   help: boolean;
 }
 
@@ -24,6 +25,7 @@ ${color.cyan('Options')}:
   --write             Write formatted files in place (default)
   --check             Check whether files are formatted
   --list-different    Print paths of unformatted files
+  --no-parallel       Disable worker parallelism
   -h, --help          Display this help message`;
 
 const parseFmtCLIArgs = (args: string[]): ParsedFmtCLIArgs => {
@@ -34,6 +36,8 @@ const parseFmtCLIArgs = (args: string[]): ParsedFmtCLIArgs => {
       check: { type: 'boolean' },
       'list-different': { type: 'boolean' },
       listDifferent: { type: 'boolean' },
+      'no-parallel': { type: 'boolean' },
+      noParallel: { type: 'boolean' },
       help: { type: 'boolean', short: 'h' },
     },
     allowPositionals: true,
@@ -51,6 +55,7 @@ const parseFmtCLIArgs = (args: string[]): ParsedFmtCLIArgs => {
   return {
     mode,
     patterns: positionals,
+    parallel: !(values['no-parallel'] || values.noParallel),
     help: values.help ?? false,
   };
 };
@@ -93,7 +98,7 @@ const logFmtResult = (result: FmtRunResult, mode: FmtMode, cwd: string): void =>
 };
 
 const runFmtCLI = async (args: string[]): Promise<void> => {
-  const { help, mode, patterns } = parseFmtCLIArgs(args);
+  const { help, mode, parallel, patterns } = parseFmtCLIArgs(args);
   if (help) {
     console.log(fmtHelpMessage);
     return;
@@ -118,7 +123,7 @@ const runFmtCLI = async (args: string[]): Promise<void> => {
       files,
       mode,
       cache: false,
-      parallel: false,
+      parallel,
     });
 
     logFmtResult(result, mode, cwd);

packages/rstack/src/fmt/parallel.ts

@@ -0,0 +1,54 @@
+// Derived from @prettier/cli, see THIRD_PARTY_NOTICES.md
+
+import { availableParallelism } from 'node:os';
+import WorkTank from 'worktank';
+
+type FmtWorkerMethods = typeof import('./worker.ts');
+
+interface FmtWorker {
+  formatFile: FmtWorkerMethods['formatFileSerial'];
+  terminate: () => void;
+}
+
+const getFmtWorkerCount = (fileCount: number): number =>
+  Math.min(fileCount, Math.max(1, availableParallelism() - 1));
+
+const getFmtWorkerUrl = (): URL => {
+  // Source tests run after build and exercise the same worker artifact as the CLI.
+  const workerPath = new URL(import.meta.url).pathname.endsWith('.ts')
+    ? '../../dist/fmtWorker.js'
+    : './fmtWorker.js';
+  return new URL(workerPath, import.meta.url);
+};
+
+/** Creates and starts every worker before formatting can begin. */
+const createFmtWorker = async (fileCount: number): Promise<FmtWorker> => {
+  const workerCount = getFmtWorkerCount(fileCount);
+  const pool = new WorkTank<FmtWorkerMethods>({
+    pool: {
+      name: 'rstack-fmt',
+      size: workerCount,
+    },
+    worker: {
+      autoInstantiate: true,
+      methods: getFmtWorkerUrl(),
+    },
+  });
+
+  try {
+    // Concurrent handshakes make WorkTank assign one task to every worker.
+    await Promise.all(
+      Array.from({ length: workerCount }, () => pool.exec('initializeFmtWorker', [])),
+    );
+  } catch (error) {
+    pool.terminate();
+    throw error;
+  }
+
+  return {
+    formatFile: (file, shouldWrite) => pool.exec('formatFileSerial', [file, shouldWrite]),
+    terminate: pool.terminate,
+  };
+};
+
+export { createFmtWorker };

packages/rstack/src/fmt/runner.ts

@@ -50,6 +50,31 @@ const runFmtFilesSerial = async (
   return results;
 };
 
+/** Processes files concurrently while preserving input order. */
+const runFmtFilesParallel = async (
+  files: FmtFileRequest[],
+  shouldWrite: boolean,
+): Promise<FmtFileResult[]> => {
+  const { createFmtWorker } = await import('./parallel.ts');
+  const worker = await createFmtWorker(files.length);
+
+  try {
+    return await Promise.all(files.map((file) => runFmtFile(file, shouldWrite, worker.formatFile)));
+  } finally {
+    worker.terminate();
+  }
+};
+
+/** Checks every worker payload before any formatting can begin. */
+const canRunFmtFilesParallel = (files: FmtFileRequest[]): boolean => {
+  try {
+    structuredClone(files);
+    return true;
+  } catch {
+    return false;
+  }
+};
+
 /** Maps file results to the Prettier-compatible CLI exit code. */
 const getFmtExitCode = (files: FmtFileResult[]): FmtExitCode => {
   let exitCode: FmtExitCode = 0;
@@ -67,9 +92,17 @@ const getFmtExitCode = (files: FmtFileResult[]): FmtExitCode => {
 };
 
 /** Runs resolved files and summarizes their outcomes for the CLI. */
-const runFmtFiles = async ({ files, mode }: RunFmtFilesOptions): Promise<FmtRunResult> => {
+const runFmtFiles = async ({
+  files,
+  mode,
+  parallel,
+}: RunFmtFilesOptions): Promise<FmtRunResult> => {
   const startTime = performance.now();
-  const results = await runFmtFilesSerial(files, mode === 'write');
+  const shouldWrite = mode === 'write';
+  const results =
+    parallel && files.length > 1 && canRunFmtFilesParallel(files)
+      ? await runFmtFilesParallel(files, shouldWrite)
+      : await runFmtFilesSerial(files, shouldWrite);
 
   return {
     files: results,

packages/rstack/src/fmt/serial.ts

@@ -1,8 +1,4 @@
-/**
- * Derived from @prettier/cli v0.12.0.
- * SPDX-License-Identifier: MIT
- * Modified by Rstack contributors.
- */
+// Derived from @prettier/cli, see THIRD_PARTY_NOTICES.md
 
 import { readFile, writeFile } from 'atomically';
 import { format } from 'prettier';

packages/rstack/src/fmt/types.ts

@@ -54,8 +54,8 @@ interface RunFmtFilesOptions {
   mode: FmtMode;
   /** Persistent cache support is added in a later implementation step. */
   cache: false;
-  /** Parallel execution support is added in a later implementation step. */
-  parallel: false;
+  /** Whether cloneable file requests should run in worker threads. */
+  parallel: boolean;
 }
 
 interface SuccessfulFmtFileResult {

packages/rstack/src/fmt/worker.ts

@@ -1,7 +1,6 @@
-/**
- * Internal build entry reserved for the fmt worker.
- *
- * The worker implementation is intentionally added by a later PR. Keeping a
- * dedicated entry now establishes a stable published asset boundary.
- */
-export {};
+import { formatFileSerial } from './serial.ts';
+
+/** Confirms that the worker module and its runtime dependencies are ready. */
+const initializeFmtWorker = (): true => true;
+
+export { formatFileSerial, initializeFmtWorker };

packages/rstack/tests/cli/fmt/index.test.ts

@@ -84,6 +84,19 @@ test('formats the current directory with Prettier defaults', () => {
   expect(readProjectFile('index.ts')).toBe('const message = "hello";\n');
 });
 
+test('supports disabling parallel execution', () => {
+  writeProjectFile('first.ts', 'const first="first"');
+  writeProjectFile('second.ts', 'const second="second"');
+
+  const result = runFmt(['--no-parallel', 'first.ts', 'second.ts']);
+
+  expect(result.status).toBe(0);
+  expect(result.stdout).toBe('first.ts\nsecond.ts\n');
+  expect(result.stderr).toBe('');
+  expect(readProjectFile('first.ts')).toBe('const first = "first";\n');
+  expect(readProjectFile('second.ts')).toBe('const second = "second";\n');
+});
+
 test('does not load Prettier config or ignore files', () => {
   writeProjectFile('.prettierrc.json', '{ "singleQuote": true, "semi": false }\n');
   writeProjectFile('.prettierignore', 'index.ts\n');