perf(fmt): load plugin resolver on demand

Author: chenjiahan

packages/rstack/src/fmt/discovery.ts

@@ -1,16 +1,11 @@
 import { resolveFmtOptions } from './config.ts';
 import { discoverFmtPaths } from './discoverPaths.ts';
 import { createFmtIgnoreMatcher } from './ignore.ts';
-import { createFmtPluginResolver, type FmtPluginResolver } from './plugins.ts';
 import type { DiscoverFmtFilesOptions, FmtFileRequest, ResolvedFmtConfig } from './types.ts';
 
-const createFileRequest = (
-  filePath: string,
-  config: ResolvedFmtConfig,
-  resolvePlugins: FmtPluginResolver,
-): FmtFileRequest => ({
+const createFileRequest = (filePath: string, config: ResolvedFmtConfig): FmtFileRequest => ({
   path: filePath,
-  options: resolvePlugins(resolveFmtOptions(filePath, config)),
+  options: resolveFmtOptions(filePath, config),
 });
 
 /** Discovers worker-ready files without reading Prettier config files or `.prettierignore`. */
@@ -26,9 +21,18 @@ const discoverFmtFiles = async ({
 
   const isFmtIgnored = createFmtIgnoreMatcher(config);
   const filePaths = candidates.filter((filePath) => !isFmtIgnored(filePath));
+  const files = filePaths.map((filePath) => createFileRequest(filePath, config));
+  if (!files.some((file) => file.options.plugins?.length)) {
+    return files;
+  }
+
+  const { createFmtPluginResolver } = await import(
+    /* rspackChunkName: 'fmtPlugins' */
+    './plugins.ts'
+  );
   const resolvePlugins = createFmtPluginResolver(config.rootPath);
 
-  return filePaths.map((filePath) => createFileRequest(filePath, config, resolvePlugins));
+  return files.map((file) => ({ ...file, options: resolvePlugins(file.options) }));
 };
 
 export { discoverFmtFiles };

packages/rstack/tests/fmt/discoveryPluginLoading.test.ts

@@ -0,0 +1,40 @@
+import { expect, rs, test } from 'rstack/test';
+import { normalizeFmtConfig } from '../../src/fmt/config.ts';
+import { discoverFmtFiles } from '../../src/fmt/discovery.ts';
+import type { FmtConfig } from '../../src/fmt/types.ts';
+import { withTempProject, writeProjectFile } from './helpers.ts';
+
+const mocks = rs.hoisted(() => ({
+  pluginResolverRoots: [] as string[],
+}));
+
+rs.mock('../../src/fmt/plugins.ts', () => ({
+  createFmtPluginResolver: (rootPath: string) => {
+    mocks.pluginResolverRoots.push(rootPath);
+    return <T>(options: T): T => options;
+  },
+}));
+
+const discover = (cwd: string, config: FmtConfig) =>
+  discoverFmtFiles({
+    cwd,
+    patterns: ['index.ts'],
+    config: normalizeFmtConfig(config, cwd),
+  });
+
+test('loads the plugin resolver only when a discovered file uses plugins', async () => {
+  await withTempProject(async (rootPath) => {
+    writeProjectFile(rootPath, 'index.ts');
+
+    await discover(rootPath, {
+      overrides: [{ files: '*.md', options: { plugins: ['missing-plugin'] } }],
+    });
+    expect(mocks.pluginResolverRoots).toEqual([]);
+
+    const files = await discover(rootPath, {
+      overrides: [{ files: '*.ts', options: { plugins: ['prettier-plugin-fixture'] } }],
+    });
+    expect(mocks.pluginResolverRoots).toEqual([rootPath]);
+    expect(files[0].options.plugins).toEqual(['prettier-plugin-fixture']);
+  });
+});