Normalize file paths for require context on Windows

packages/metro/src/lib/__tests__/__snapshots__/contextModuleTemplates-test.js.snap

@@ -5,11 +5,11 @@ exports[`getContextModuleTemplate creates a lazy template 1`] = `
 const map = Object.defineProperties({}, {
   \\"./foo.js\\": { enumerable: true, get() { return import(\\"/path/to/project/src/foo.js\\"); } },
 });
-  
+
 function metroContext(request) {
     return map[request];
 }
-  
+
 // Return the keys that can be resolved.
 metroContext.keys = function metroContextKeys() {
   return Object.keys(map);
@@ -29,11 +29,11 @@ const map = Object.defineProperties({}, {
   \\"./another/bar.js\\": { enumerable: true, get() { return import(\\"/path/to/project/src/another/bar.js\\"); } },
   \\"./foo.js\\": { enumerable: true, get() { return import(\\"/path/to/project/src/foo.js\\"); } },
 });
-  
+
 function metroContext(request) {
     return map[request];
 }
-  
+
 // Return the keys that can be resolved.
 metroContext.keys = function metroContextKeys() {
   return Object.keys(map);
@@ -52,11 +52,11 @@ exports[`getContextModuleTemplate creates a sync template 1`] = `
 const map = Object.defineProperties({}, {
   \\"./foo.js\\": { enumerable: true, get() { return require(\\"/path/to/project/src/foo.js\\"); } },
 });
-  
+
 function metroContext(request) {
     return map[request];
 }
-  
+
 // Return the keys that can be resolved.
 metroContext.keys = function metroContextKeys() {
   return Object.keys(map);
@@ -75,13 +75,13 @@ exports[`getContextModuleTemplate creates an eager template 1`] = `
 const map = Object.defineProperties({}, {
   \\"./foo.js\\": { enumerable: true, get() { return require(\\"/path/to/project/src/foo.js\\"); } },
 });
-  
+
 function metroContext(request) {
     // Here Promise.resolve().then() is used instead of new Promise() to prevent
   // uncaught exception popping up in devtools
   return Promise.resolve().then(() => map[request]);
 }
-  
+
 // Return the keys that can be resolved.
 metroContext.keys = function metroContextKeys() {
   return Object.keys(map);
@@ -113,3 +113,26 @@ metroEmptyContext.resolve = function metroContextResolve(request) {
 
 module.exports = metroEmptyContext;"
 `;
+
+exports[`getContextModuleTemplate creates posix paths on windows for sync template 1`] = `
+"// All of the requested modules are loaded behind enumerable getters.
+const map = Object.defineProperties({}, {
+  \\"./foo.js\\": { enumerable: true, get() { return require(\\"C:\\\\\\\\path\\\\\\\\to\\\\\\\\project\\\\\\\\src\\\\\\\\foo.js\\"); } },
+});
+
+function metroContext(request) {
+    return map[request];
+}
+
+// Return the keys that can be resolved.
+metroContext.keys = function metroContextKeys() {
+  return Object.keys(map);
+};
+
+// Return the module identifier for a user request.
+metroContext.resolve = function metroContextResolve(request) {
+  throw new Error('Unimplemented Metro module context functionality');
+}
+
+module.exports = metroContext;"
+`;

packages/metro/src/lib/__tests__/contextModuleTemplates-test.js

@@ -49,4 +49,17 @@ describe('getContextModuleTemplate', () => {
 
     expect(template).toMatchSnapshot();
   });
+
+  test('creates posix paths on windows for sync template', () => {
+    jest.resetModules();
+    jest.mock('path', () => jest.requireActual('path').win32);
+    const {
+      getContextModuleTemplate: getWindowsTemplate,
+    } = require('../contextModuleTemplates');
+    const template = getWindowsTemplate('sync', 'c:/path/to/project/src', [
+      'C:\\path\\to\\project\\src\\foo.js',
+    ]);
+    expect(template).toMatch(/foo\.js/);
+    expect(template).toMatchSnapshot();
+  });
 });

packages/metro/src/lib/contextModuleTemplates.js

@@ -10,6 +10,7 @@
  */
 
 import * as path from 'path';
+import * as os from 'os';
 import type {ContextMode} from '../ModuleGraph/worker/collectDependencies';
 
 function createFileMap(
@@ -26,14 +27,19 @@ function createFileMap(
     .forEach(file => {
       let filePath = path.relative(modulePath, file);
 
+      if (os.platform() === 'win32') {
+        filePath = filePath.replace(/\\/g, '/');
+      }
+
       // NOTE(EvanBacon): I'd prefer we prevent the ability for a module to require itself (`require.context('./')`)
       // but Webpack allows this, keeping it here provides better parity between bundlers.
 
       // Ensure relative file paths start with `./` so they match the
       // patterns (filters) used to include them.
       if (!filePath.startsWith('.')) {
-        filePath = `.${path.sep}` + filePath;
+        filePath = `./${filePath}`;
       }
+
       const key = JSON.stringify(filePath);
       // NOTE(EvanBacon): Webpack uses `require.resolve` in order to load modules on demand,
       // Metro doesn't have this functionality so it will use getters instead. Modules need to
@@ -79,11 +85,11 @@ const map = ${createFileMap(
     files,
     moduleId => `${importSyntax}(${JSON.stringify(moduleId)})`,
   )};
-  
+
 function metroContext(request) {
   ${getContextTemplate}
 }
-  
+
 // Return the keys that can be resolved.
 metroContext.keys = function metroContextKeys() {
   return Object.keys(map);