fix(metro): normalize remaining Windows path comparisons

.changeset/metro-windows-path-comparisons.md

@@ -0,0 +1,5 @@
+---
+'@module-federation/metro': patch
+---
+
+fix(metro): normalize remaining Windows path comparisons in the resolver and babel plugin. The init-host/remote-entry origin-module checks, the patched HMRClient check, and the babel plugin's `blacklistedPaths`/`state.filename` check now compare POSIX-normalized paths so they match correctly on Windows, where Metro and `path.resolve` can disagree on path separators.

packages/metro-core/__tests__/plugin/resolver.spec.ts

@@ -168,4 +168,46 @@ describe('createResolveRequest', () => {
       expect(fallbackResolver).not.toHaveBeenCalled();
     },
   );
+
+  it('matches the init-host origin module path regardless of separator (Windows)', () => {
+    // Metro and `path.resolve` can disagree on path separators on Windows.
+    // The generated init-host path uses native (backslash) separators while
+    // the origin module path reported by Metro may use POSIX separators.
+    const projectDir = 'C:\\project';
+    const tmpDir = 'C:\\project\\node_modules\\.mf-metro';
+    const initHost = 'C:\\project\\node_modules\\.mf-metro\\init-host.js';
+    const config = createConfig('lodash', 'lodash');
+    const fallbackResolver = vi.fn<CustomResolver>(() => ({
+      type: 'sourceFile',
+      filePath: '/fallback.js',
+    }));
+    // Metro reports the same file using POSIX separators
+    const context = createResolverContext(
+      'C:/project/node_modules/.mf-metro/init-host.js',
+      fallbackResolver,
+    );
+    const vmManager: Pick<VirtualModuleManager, 'registerVirtualModule'> = {
+      registerVirtualModule: vi.fn(),
+    };
+
+    const resolveRequest = createResolveRequest({
+      isRemote: false,
+      hacks: { patchHMRClient: false, patchInitializeCore: false },
+      options: config,
+      paths: {
+        ...createPaths(projectDir, tmpDir),
+        initHost,
+      },
+      vmManager,
+    });
+
+    const resolved = resolveRequest(context, 'lodash', 'ios');
+
+    // init-host imports its shared deps directly, so the request should fall
+    // through to the host resolver instead of being rewritten to a virtual
+    // shared module.
+    expect(resolved).toEqual({ type: 'sourceFile', filePath: '/fallback.js' });
+    expect(fallbackResolver).toHaveBeenCalledTimes(1);
+    expect(vmManager.registerVirtualModule).not.toHaveBeenCalled();
+  });
 });

packages/metro-core/babel-plugin/index.js

@@ -80,12 +80,23 @@ function getRejectedPromise(errorMessage) {
   );
 }
 
+// normalize paths to POSIX separators so comparisons against generated
+// paths work on Windows, where Metro and `path.resolve` can disagree
+// on path separators
+function toPosixPath(value) {
+  return typeof value === 'string' ? value.replace(/\\/g, '/') : value;
+}
+
 function moduleFederationMetroBabelPlugin() {
   return {
     name: 'module-federation-metro-babel-plugin',
     visitor: {
       CallExpression(path, state) {
-        if (state.opts.blacklistedPaths.includes(state.filename)) {
+        const filename = toPosixPath(state.filename);
+        const blacklistedPaths = (state.opts.blacklistedPaths || []).map(
+          toPosixPath,
+        );
+        if (blacklistedPaths.includes(filename)) {
           return;
         }
 

packages/metro-core/src/plugin/resolver.ts

@@ -64,6 +64,11 @@ export function createResolveRequest({
   });
 
   return function resolveRequest(context, moduleName, platform) {
+    // normalize the origin module path so comparisons against generated
+    // paths work on Windows, where Metro and `path.resolve` can disagree
+    // on path separators
+    const originModulePath = toPosixPath(context.originModulePath);
+
     // virtual entrypoint for host
     if (moduleName.match(hostEntryPathRegex)) {
       const hostEntryGenerator = () =>
@@ -119,7 +124,7 @@ export function createResolveRequest({
     }
 
     // shared modules handling in init-host.js
-    if ([paths.initHost].includes(context.originModulePath)) {
+    if (toPosixPath(paths.initHost) === originModulePath) {
       // init-host contains definition of shared modules so we need to prevent
       // circular import of shared module, by allowing import shared dependencies directly
       return customResolver
@@ -128,7 +133,7 @@ export function createResolveRequest({
     }
 
     // shared modules handling in remote-entry.js
-    if ([paths.remoteEntry].includes(context.originModulePath)) {
+    if (toPosixPath(paths.remoteEntry) === originModulePath) {
       const sharedModule = options.shared[moduleName];
       // import: false means that the module is marked as external
       if (sharedModule && sharedModule.import === false) {
@@ -192,7 +197,7 @@ export function createResolveRequest({
     if (
       hacks.patchHMRClient &&
       moduleName.endsWith('HMRClient') &&
-      context.originModulePath !== resolveModule('HMRClient.ts')
+      originModulePath !== toPosixPath(resolveModule('HMRClient.ts'))
     ) {
       const res = customResolver
         ? customResolver(context, moduleName, platform)