fix(test runner): allow directory imports with path mapping

This regressed in #32078.

packages/playwright-ct-core/src/vitePlugin.ts

@@ -262,7 +262,7 @@ function vitePlugin(registerSource: string, templateDir: string, buildInfo: Buil
 
     async writeBundle(this: PluginContext) {
       for (const importInfo of importInfos.values()) {
-        const importPath = resolveHook(importInfo.filename, importInfo.importSource, true);
+        const importPath = resolveHook(importInfo.filename, importInfo.importSource);
         if (!importPath)
           continue;
         const deps = new Set<string>();

packages/playwright-ct-core/src/viteUtils.ts

@@ -147,13 +147,13 @@ export async function populateComponentsFromTests(componentRegistry: ComponentRe
     for (const importInfo of importList)
       componentRegistry.set(importInfo.id, importInfo);
     if (componentsByImportingFile)
-      componentsByImportingFile.set(file, importList.map(i => resolveHook(i.filename, i.importSource, true)).filter(Boolean) as string[]);
+      componentsByImportingFile.set(file, importList.map(i => resolveHook(i.filename, i.importSource)).filter(Boolean) as string[]);
   }
 }
 
 export function hasJSComponents(components: ImportInfo[]): boolean {
   for (const component of components) {
-    const importPath = resolveHook(component.filename, component.importSource, true);
+    const importPath = resolveHook(component.filename, component.importSource);
     const extname = importPath ? path.extname(importPath) : '';
     if (extname === '.js' || (importPath && !extname && fs.existsSync(importPath + '.js')))
       return true;
@@ -183,7 +183,7 @@ export function transformIndexFile(id: string, content: string, templateDir: str
   lines.push(registerSource);
 
   for (const value of importInfos.values()) {
-    const importPath = resolveHook(value.filename, value.importSource, true) || value.importSource;
+    const importPath = resolveHook(value.filename, value.importSource) || value.importSource;
     lines.push(`const ${value.id} = () => import('${importPath?.replaceAll(path.sep, '/')}').then((mod) => mod.${value.remoteName || 'default'});`);
   }
 

packages/playwright/src/transform/esmLoader.ts

@@ -26,7 +26,7 @@ import { fileIsModule } from '../util';
 async function resolve(specifier: string, context: { parentURL?: string }, defaultResolve: Function) {
   if (context.parentURL && context.parentURL.startsWith('file://')) {
     const filename = url.fileURLToPath(context.parentURL);
-    const resolved = resolveHook(filename, specifier, true);
+    const resolved = resolveHook(filename, specifier);
     if (resolved !== undefined)
       specifier = url.pathToFileURL(resolved).toString();
   }

packages/playwright/src/transform/transform.ts

@@ -129,20 +129,19 @@ function loadAndValidateTsconfigsForFolder(folder: string): ParsedTsConfigData[]
 const pathSeparator = process.platform === 'win32' ? ';' : ':';
 const builtins = new Set(Module.builtinModules);
 
-export function resolveHook(filename: string, specifier: string, isESM: boolean): string | undefined {
+export function resolveHook(filename: string, specifier: string): string | undefined {
   if (specifier.startsWith('node:') || builtins.has(specifier))
     return;
   if (!shouldTransform(filename))
     return;
 
   if (isRelativeSpecifier(specifier))
-    return resolveImportSpecifierExtension(path.resolve(path.dirname(filename), specifier), false, isESM);
+    return resolveImportSpecifierExtension(path.resolve(path.dirname(filename), specifier), false);
 
   /**
    * TypeScript discourages path-mapping into node_modules
    *    (https://www.typescriptlang.org/docs/handbook/modules/reference.html#paths-should-not-point-to-monorepo-packages-or-node_modules-packages).
-   * It seems like TypeScript tries path-mapping first, but does not look at the `package.json` or `index.js` files in ESM.
-   * If path-mapping doesn't yield a result, TypeScript falls back to the default resolution (typically node_modules).
+   * However, if path-mapping doesn't yield a result, TypeScript falls back to the default resolution (typically node_modules).
    */
   const isTypeScript = filename.endsWith('.ts') || filename.endsWith('.tsx');
   const tsconfigs = loadAndValidateTsconfigsForFile(filename);
@@ -185,7 +184,7 @@ export function resolveHook(filename: string, specifier: string, isESM: boolean)
         if (value.includes('*'))
           candidate = candidate.replace('*', matchedPartOfSpecifier);
         candidate = path.resolve(tsconfig.pathsBase!, candidate);
-        const existing = resolveImportSpecifierExtension(candidate, true, isESM);
+        const existing = resolveImportSpecifierExtension(candidate, true);
         if (existing) {
           longestPrefixLength = keyPrefix.length;
           pathMatchedByLongestPrefix = existing;
@@ -199,7 +198,7 @@ export function resolveHook(filename: string, specifier: string, isESM: boolean)
   if (path.isAbsolute(specifier)) {
     // Handle absolute file paths like `import '/path/to/file'`
     // Do not handle module imports like `import 'fs'`
-    return resolveImportSpecifierExtension(specifier, false, isESM);
+    return resolveImportSpecifierExtension(specifier, false);
   }
 }
 
@@ -281,7 +280,7 @@ function installTransformIfNeeded() {
   const originalResolveFilename = (Module as any)._resolveFilename;
   function resolveFilename(this: any, specifier: string, parent: Module, ...rest: any[]) {
     if (parent) {
-      const resolved = resolveHook(parent.filename, specifier, false);
+      const resolved = resolveHook(parent.filename, specifier);
       if (resolved !== undefined)
         specifier = resolved;
     }

packages/playwright/src/util.ts

@@ -307,6 +307,20 @@ function folderIsModule(folder: string): boolean {
   return require(packageJsonPath).type === 'module';
 }
 
+const packageJsonMainFieldCache = new Map<string, string | undefined>();
+
+function getMainFieldFromPackageJson(packageJsonPath: string) {
+  if (!packageJsonMainFieldCache.has(packageJsonPath)) {
+    let mainField: string | undefined;
+    try {
+      mainField = JSON.parse(fs.readFileSync(packageJsonPath, 'utf8')).main;
+    } catch {
+    }
+    packageJsonMainFieldCache.set(packageJsonPath, mainField);
+  }
+  return packageJsonMainFieldCache.get(packageJsonPath);
+}
+
 // This follows the --moduleResolution=bundler strategy from tsc.
 // https://devblogs.microsoft.com/typescript/announcing-typescript-5-0-beta/#moduleresolution-bundler
 const kExtLookups = new Map([
@@ -316,7 +330,7 @@ const kExtLookups = new Map([
   ['.mjs', ['.mts']],
   ['', ['.js', '.ts', '.jsx', '.tsx', '.cjs', '.mjs', '.cts', '.mts']],
 ]);
-export function resolveImportSpecifierExtension(resolved: string, isPathMapping: boolean, isESM: boolean): string | undefined {
+export function resolveImportSpecifierExtension(resolved: string, isPathMapping: boolean): string | undefined {
   if (fileExists(resolved))
     return resolved;
 
@@ -331,25 +345,34 @@ export function resolveImportSpecifierExtension(resolved: string, isPathMapping:
     break;  // Do not try '' when a more specific extension like '.jsx' matched.
   }
 
-  // After TypeScript path mapping, here's how directories with a `package.json` are resolved:
-  //  - `package.json#exports` is not respected
-  //  - `package.json#main` is respected only in CJS mode
-  //  - `index.js` default is respected only in CJS mode
-  //
-  // More info:
-  //  - https://www.typescriptlang.org/docs/handbook/modules/reference.html#paths-should-not-point-to-monorepo-packages-or-node_modules-packages
-  //  - https://www.typescriptlang.org/docs/handbook/modules/reference.html#directory-modules-index-file-resolution
-  //  - https://nodejs.org/dist/latest-v20.x/docs/api/modules.html#folders-as-modules
-
-  const shouldNotResolveDirectory = isPathMapping && isESM;
+  if (dirExists(resolved)) {
+    const packageJsonPath = path.join(resolved, 'package.json');
+
+    if (isPathMapping) {
+      // After TypeScript path mapping, here's how directories with a `package.json` are resolved,
+      // assuming "moduleResolution": "bundler" that we follow:
+      //  - `package.json#exports` is not respected
+      //  - `package.json#main` is respected
+      //  - `index.js` default is respected
+      //
+      // More info:
+      //  - https://www.typescriptlang.org/docs/handbook/modules/reference.html#paths-should-not-point-to-monorepo-packages-or-node_modules-packages
+      //  - https://www.typescriptlang.org/docs/handbook/modules/reference.html#directory-modules-index-file-resolution
+      //  - https://nodejs.org/dist/latest-v20.x/docs/api/modules.html#folders-as-modules
+
+      const mainField = getMainFieldFromPackageJson(packageJsonPath);
+      const mainFieldResolved = mainField ? resolveImportSpecifierExtension(path.resolve(resolved, mainField), isPathMapping) : undefined;
+      return mainFieldResolved || resolveImportSpecifierExtension(path.join(resolved, 'index'), isPathMapping);
+    }
 
-  if (!shouldNotResolveDirectory && dirExists(resolved)) {
     // If we import a package, let Node.js figure out the correct import based on package.json.
-    if (fileExists(path.join(resolved, 'package.json')))
+    if (fileExists(packageJsonPath))
       return resolved;
 
+    // Fallback to "folder as module" Node.js behavior.
+    // https://nodejs.org/dist/latest-v20.x/docs/api/modules.html#folders-as-modules
     const dirImport = path.join(resolved, 'index');
-    return resolveImportSpecifierExtension(dirImport, isPathMapping, isESM);
+    return resolveImportSpecifierExtension(dirImport, isPathMapping);
   }
 }
 

tests/playwright-test/playwright-test-fixtures.ts

@@ -367,8 +367,8 @@ export const test = base
 const TSCONFIG = {
   'compilerOptions': {
     'target': 'ESNext',
-    'moduleResolution': 'node',
-    'module': 'commonjs',
+    'moduleResolution': 'bundler',
+    'module': 'esnext',
     'strict': true,
     'esModuleInterop': true,
     'allowSyntheticDefaultImports': true,