Keep the file extension in async bundle paths

packages/metro/src/DeltaBundler/Serializers/helpers/__tests__/js-test.js

@@ -12,6 +12,7 @@
 import type {Dependency} from '../../../types';
 
 import CountingSet from '../../../../lib/CountingSet';
+import parseBundleOptionsFromBundleRequestUrl from '../../../../lib/parseBundleOptionsFromBundleRequestUrl';
 import {inlineModuleIdReferences, wrapModule} from '../js';
 import {wrap as raw} from 'jest-snapshot-serializer-raw';
 import createModuleIdFactory from 'metro-config/private/defaults/createModuleIdFactory';
@@ -149,7 +150,7 @@ describe('wrapModule()', () => {
         }),
       ),
     ).toMatchInlineSnapshot(
-      `__d(function() { console.log("foo") },0,{"0":1,"1":2,"paths":{"1":"/../bar.bundle?param1=true&param2=1234&modulesOnly=true&runModule=false"}});`,
+      `__d(function() { console.log("foo") },0,{"0":1,"1":2,"paths":{"1":"/../bar.js.bundle?param1=true&param2=1234&modulesOnly=true&runModule=false"}});`,
     );
   });
 
@@ -171,10 +172,42 @@ describe('wrapModule()', () => {
         }),
       ),
     ).toMatchInlineSnapshot(
-      `__d(function() { console.log("foo") },0,{"0":1,"1":2,"paths":{"1":"/bar.bundle?param1=true&param2=1234&modulesOnly=true&runModule=false"}});`,
+      `__d(function() { console.log("foo") },0,{"0":1,"1":2,"paths":{"1":"/bar.js.bundle?param1=true&param2=1234&modulesOnly=true&runModule=false"}});`,
     );
   });
 
+  test('async dependency paths keep the resolved file extension', () => {
+    myModule.dependencies.set('bar', {
+      absolutePath: '/root/node_modules/bar/dist/index.cjs',
+      data: {
+        data: {asyncType: 'async', isESMImport: false, locs: [], key: 'bar'},
+        name: 'bar',
+      },
+    });
+    const sourceUrl = 'http://localhost/Main.bundle?platform=ios';
+    const wrapped = wrapModule(myModule, {
+      createModuleId: createModuleIdFactory(),
+      dev: false,
+      includeAsyncPaths: true,
+      projectRoot: '/root',
+      serverRoot: '/root',
+      sourceUrl,
+    });
+    expect(raw(wrapped)).toMatchInlineSnapshot(
+      `__d(function() { console.log("foo") },0,{"0":1,"1":2,"paths":{"1":"/node_modules/bar/dist/index.cjs.bundle?platform=ios&modulesOnly=true&runModule=false"}});`,
+    );
+
+    // The server must resolve the chunk URL back to the same file, not to a
+    // sibling such as `index.js` found through `sourceExts`.
+    const asyncPath = nullthrows(wrapped.match(/"paths":\{"1":"([^"]+)"/))[1];
+    expect(
+      parseBundleOptionsFromBundleRequestUrl(
+        'http://localhost' + asyncPath,
+        new Set(['ios']),
+      ).entryFile,
+    ).toBe('./node_modules/bar/dist/index.cjs');
+  });
+
   test('async bundle paths override modulesOnly and runModule', () => {
     const dep = nullthrows(myModule.dependencies.get('bar'));
     myModule.dependencies.set('bar', {
@@ -194,7 +227,7 @@ describe('wrapModule()', () => {
         }),
       ),
     ).toMatchInlineSnapshot(
-      `__d(function() { console.log("foo") },0,{"0":1,"1":2,"paths":{"1":"/../bar.bundle?modulesOnly=true&runModule=false"}});`,
+      `__d(function() { console.log("foo") },0,{"0":1,"1":2,"paths":{"1":"/../bar.js.bundle?modulesOnly=true&runModule=false"}});`,
     );
   });
 
@@ -318,7 +351,7 @@ describe('wrapModule() with inlined module ids', () => {
       `__d(function(g,r,i,a,m,e,${NAME}){r(${'1'.padEnd(
         ref(0).length,
       )});r(${'2'.padEnd(ref(1).length)})},0,` +
-        `{"paths":{"1":"/../bar.bundle?param1=true&modulesOnly=true&runModule=false"}});`,
+        `{"paths":{"1":"/../bar.js.bundle?param1=true&modulesOnly=true&runModule=false"}});`,
     );
   });
 

packages/metro/src/DeltaBundler/Serializers/helpers/js.js

@@ -108,12 +108,11 @@ function getDefaultAsyncDependencyPath(
   const bundlePath = path.relative(options.serverRoot, dependency.absolutePath);
   return (
     '/' +
-    path.join(
-      // TODO: This is not the proper Metro URL encoding of a file path
-      path.dirname(bundlePath),
-      // Strip the file extension
-      path.basename(bundlePath, path.extname(bundlePath)),
-    ) +
+    // TODO: This is not the proper Metro URL encoding of a file path
+    // Keep the file extension: the server strips only the `.bundle` suffix, so
+    // the chunk resolves to this exact file and not to a sibling found through
+    // `sourceExts` (e.g. `index.js` instead of `index.cjs`).
+    normalizePathSeparatorsToPosix(bundlePath) +
     '.bundle?' +
     searchParams.toString()
   );

packages/metro/src/integration_tests/__tests__/server-test.js

@@ -99,10 +99,10 @@ describe('Metro development server serves bundles via HTTP', () => {
     expect(bundlesDownloaded).toEqual(
       new Set([
         '/import-export/index.bundle?platform=ios&dev=true&minify=false&lazy=true',
-        '/import-export/export-5.bundle?platform=ios&dev=true&minify=false&lazy=true&modulesOnly=true&runModule=false',
-        '/import-export/export-6.bundle?platform=ios&dev=true&minify=false&lazy=true&modulesOnly=true&runModule=false',
-        '/import-export/export-7.bundle?platform=ios&dev=true&minify=false&lazy=true&modulesOnly=true&runModule=false',
-        '/import-export/export-8.bundle?platform=ios&dev=true&minify=false&lazy=true&modulesOnly=true&runModule=false',
+        '/import-export/export-5.js.bundle?platform=ios&dev=true&minify=false&lazy=true&modulesOnly=true&runModule=false',
+        '/import-export/export-6.js.bundle?platform=ios&dev=true&minify=false&lazy=true&modulesOnly=true&runModule=false',
+        '/import-export/export-7.js.bundle?platform=ios&dev=true&minify=false&lazy=true&modulesOnly=true&runModule=false',
+        '/import-export/export-8.js.bundle?platform=ios&dev=true&minify=false&lazy=true&modulesOnly=true&runModule=false',
       ]),
     );
   });