Respect unstable_serverRoot setting in experimentalImportBundleSupport mode

Summary:
There was a bug when serving bundles in `experimentalImportBundleSupport: true` mode (D15943150 (72329d0), aka development-mode bundle splitting) and using a non-empty `unstable_serverRoot` (D30247868 (026a66c)). The split bundles would be requested with the wrong URL, using `projectRoot` rather than `unstable_serverRoot` as the base path.

Here we fix this bug by adding a `serverRoot` property to the serializer's input and using it as the base path for split bundle URLs. We add `serverRoot` *alongside* `projectRoot` in order to avoid breaking custom serializers that may rely on `projectRoot`'s existence.

Reviewed By: GijsWeterings

Differential Revision: D35188943

fbshipit-source-id: 666943d90f5af613dbc366cf10861d7313ddd3c5

Author: motiz88

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

@@ -309,6 +309,7 @@ it('adds lazy imports at the end of a bundle', () => {
         projectRoot: '/root',
         runBeforeMainModule: [],
         runModule: true,
+        serverRoot: '/root',
         sourceMapUrl: 'http://localhost/bundle.map',
       },
     ),
@@ -331,3 +332,49 @@ it('adds lazy imports at the end of a bundle', () => {
     }
   `);
 });
+
+it('lazy imports are relative to serverRoot if it differs from projectRoot', () => {
+  expect(
+    baseJSBundle(
+      '/root/foo',
+      [polyfill],
+      {
+        dependencies: new Map([
+          ['/root/foo', fooModule],
+          ['/root/bar', barModule],
+        ]),
+        entryPoints: ['foo'],
+        importBundleNames: new Set(['/path/to/async/module.js']),
+      },
+      {
+        asyncRequireModulePath: '/asyncRequire.js',
+        processModuleFilter: () => true,
+        createModuleId: filePath => path.basename(filePath),
+        dev: true,
+        getRunModuleStatement,
+        projectRoot: '/root',
+        runBeforeMainModule: [],
+        runModule: true,
+        serverRoot: '/',
+        sourceMapUrl: 'http://localhost/bundle.map',
+      },
+    ),
+  ).toMatchInlineSnapshot(`
+    Object {
+      "modules": Array [
+        Array [
+          "foo",
+          "__d(function() {/* code for foo */},\\"foo\\",[\\"bar\\"],\\"foo\\");",
+        ],
+        Array [
+          "bar",
+          "__d(function() {/* code for bar */},\\"bar\\",[],\\"bar\\");",
+        ],
+      ],
+      "post": "(function(){var $$=require(\\"asyncRequire.js\\");$$.addImportBundleNames({\\"module.js\\":\\"path/to/async/module\\"})})();
+    require(\\"foo\\");
+    //# sourceMappingURL=http://localhost/bundle.map",
+      "pre": "__d(function() {/* code for polyfill */});",
+    }
+  `);
+});

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

@@ -63,6 +63,7 @@ function baseBytecodeBundle(
         projectRoot: options.projectRoot,
         runBeforeMainModule: options.runBeforeMainModule,
         runModule: options.runModule,
+        serverRoot: options.serverRoot,
         sourceMapUrl: options.sourceMapUrl,
         sourceUrl: options.sourceUrl,
       },

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

@@ -65,6 +65,7 @@ function baseJSBundle(
         projectRoot: options.projectRoot,
         runBeforeMainModule: options.runBeforeMainModule,
         runModule: options.runModule,
+        serverRoot: options.serverRoot,
         sourceMapUrl: options.sourceMapUrl,
         sourceUrl: options.sourceUrl,
       },

packages/metro/src/DeltaBundler/types.flow.js

@@ -129,6 +129,7 @@ export type SerializerOptions = {|
   +projectRoot: string,
   +runBeforeMainModule: $ReadOnlyArray<string>,
   +runModule: boolean,
+  +serverRoot: string,
   +sourceMapUrl: ?string,
   +sourceUrl: ?string,
 |};

packages/metro/src/Server.js

@@ -210,6 +210,8 @@ class Server {
       sourceMapUrl: serializerOptions.sourceMapUrl,
       sourceUrl: serializerOptions.sourceUrl,
       inlineSourceMap: serializerOptions.inlineSourceMap,
+      serverRoot:
+        this._config.server.unstable_serverRoot ?? this._config.projectRoot,
     };
     let bundleCode = null;
     let bundleMap = null;
@@ -285,6 +287,8 @@ class Server {
       sourceMapUrl: serializerOptions.sourceMapUrl,
       sourceUrl: serializerOptions.sourceUrl,
       inlineSourceMap: serializerOptions.inlineSourceMap,
+      serverRoot:
+        this._config.server.unstable_serverRoot ?? this._config.projectRoot,
     });
   }
 
@@ -754,6 +758,8 @@ class Server {
           sourceMapUrl: serializerOptions.sourceMapUrl,
           sourceUrl: serializerOptions.sourceUrl,
           inlineSourceMap: serializerOptions.inlineSourceMap,
+          serverRoot:
+            this._config.server.unstable_serverRoot ?? this._config.projectRoot,
         },
       );
 
@@ -862,6 +868,8 @@ class Server {
           sourceMapUrl: serializerOptions.sourceMapUrl,
           sourceUrl: serializerOptions.sourceUrl,
           inlineSourceMap: serializerOptions.inlineSourceMap,
+          serverRoot:
+            this._config.server.unstable_serverRoot ?? this._config.projectRoot,
         }),
       );
 

packages/metro/src/lib/getAppendScripts.js

@@ -24,6 +24,7 @@ type Options<T: number | string> = {
   +getRunModuleStatement: T => string,
   +inlineSourceMap: ?boolean,
   +projectRoot: string,
+  +serverRoot: string,
   +runBeforeMainModule: $ReadOnlyArray<string>,
   +runModule: boolean,
   +sourceMapUrl: ?string,
@@ -42,7 +43,7 @@ function getAppendScripts<T: number | string>(
   if (importBundleNames.size) {
     const importBundleNamesObject = Object.create(null);
     importBundleNames.forEach(absolutePath => {
-      const bundlePath = path.relative(options.projectRoot, absolutePath);
+      const bundlePath = path.relative(options.serverRoot, absolutePath);
       importBundleNamesObject[options.createModuleId(absolutePath)] =
         bundlePath.slice(0, -path.extname(bundlePath).length);
     });