experimentalImportSupport: Place export-all assignments before explicit exports, fix precedence of export default > export * from

packages/metro-transform-plugins/src/__tests__/import-export-plugin-test.js

@@ -9,14 +9,16 @@
  * @oncall react_native
  */
 
 import type {Dependency} from 'metro/private/ModuleGraph/worker/collectDependencies';
 
 import collectDependencies from 'metro/private/ModuleGraph/worker/collectDependencies';
 
 const {compare, transformToAst} = require('../__mocks__/test-helpers');
 const importExportPlugin = require('../import-export-plugin');
+const generate = require('@babel/generator').default;
 // $FlowFixMe[untyped-import] @babel/code-frame
 const {codeFrameColumns} = require('@babel/code-frame');
+const vm = require('vm');
 
 const opts = {
   importAll: '_$$_IMPORT_ALL',
@@ -156,8 +158,8 @@
 
     var _foo = require('bar').foo;
     var _baz = require('bar').baz;
-    exports.default = _foo;
     exports.baz = _baz;
+    exports.default = _foo;
   `;
 
   compare([importExportPlugin], code, expected, opts);
@@ -233,8 +235,8 @@
     exports.bar = 'bar';
     module.exports.baz = 'baz';
     class _default {}
-    exports.default = _default;
     exports.foo = foo;
+    exports.default = _default;
   `;
 
   compare([importExportPlugin], code, expected, opts);
@@ -360,6 +362,69 @@
   `);
 });
 
+test('places export all above explicit exports', () => {
+  const code = `
+    export * from 'foo';
+    export {baz} from 'bar';
+    const bax = 'bax';
+    export default bax;
+  `;
+
+  const expected = `
+    Object.defineProperty(exports, '__esModule', {value: true});
+
+    var _baz = require('bar').baz;
+    const bax = 'bax';
+
+    var _default = bax;
+
+    var _foo = require("foo");
+
+    for (var _key in _foo) {
+      exports[_key] = _foo[_key];
+    }
+
+    exports.baz = _baz;
+    exports.default = _default;
+  `;
+
+  compare([importExportPlugin], code, expected, opts);
+});
+
+test('explicit exports override export all at runtime', () => {
+  const transformedCode = generate(
+    transformToAst(
+      [importExportPlugin],
+      `
+        export * from 'foo';
+        export const overridden = 'explicit named';
+        export default 'explicit default';
+      `,
+      opts,
+    ),
+  ).code;
+  const context = {
+    exports: {} as {[string]: unknown},
+    require: (id: string) => {
+      if (id !== 'foo') {
+        throw new Error(`Unexpected module: ${id}`);
+      }
+      return {
+        default: 'star default',
+        overridden: 'star named',
+        sourceOnly: 'source only',
+      };
+    },
+  };
+
+  vm.runInNewContext(transformedCode, context);
+
+  expect(context.exports.__esModule).toBe(true);
+  expect(context.exports.default).toBe('explicit default');
+  expect(context.exports.overridden).toBe('explicit named');
+  expect(context.exports.sourceOnly).toBe('source only');
+});
+
 test('enables module exporting when something is exported', () => {
   const code = `
     foo();

packages/metro-transform-plugins/src/import-export-plugin.js

@@ -522,20 +522,6 @@ export default function importExportPlugin({
             body.unshift(e.node);
           });
 
-          state.exportDefault.forEach(
-            (e: {local: string, loc: ?SourceLocation, ...}) => {
-              body.push(
-                withLocation(
-                  exportTemplate({
-                    LOCAL: t.identifier(e.local),
-                    REMOTE: t.identifier('default'),
-                  }),
-                  e.loc,
-                ),
-              );
-            },
-          );
-
           state.exportAll.forEach(
             (e: {file: string, loc: ?SourceLocation, ...}) => {
               body.push(
@@ -569,6 +555,20 @@ export default function importExportPlugin({
             },
           );
 
+          state.exportDefault.forEach(
+            (e: {local: string, loc: ?SourceLocation, ...}) => {
+              body.push(
+                withLocation(
+                  exportTemplate({
+                    LOCAL: t.identifier(e.local),
+                    REMOTE: t.identifier('default'),
+                  }),
+                  e.loc,
+                ),
+              );
+            },
+          );
+
           if (
             state.exportDefault.length ||
             state.exportAll.length ||

packages/metro/src/integration_tests/__tests__/__snapshots__/import-export-test.js.snap

@@ -20,6 +20,9 @@ Object {
     "arrayRest": Array [
       "export-destructuring: ARRAY_REST",
     ],
+    "exportStarDefault": "export-star-overrides: DEFAULT",
+    "exportStarOverridden": "export-star-overrides: OVERRIDDEN",
+    "exportStarSourceOnly": "export-star-source: SOURCE_ONLY",
     "foo": "export-null: FOO",
     "importStar": Object {
       "default": "export-2: DEFAULT",

packages/metro/src/integration_tests/__tests__/import-export-test.js

@@ -39,6 +39,15 @@ test('builds a simple bundle', async () => {
   ]);
   expect(object.extraData.namespaceReExportDefault).toBe('export-2: DEFAULT');
   expect(object.extraData.namespaceReExportFoo).toBe('export-2: FOO');
+  expect(object.extraData.exportStarDefault).toBe(
+    'export-star-overrides: DEFAULT',
+  );
+  expect(object.extraData.exportStarOverridden).toBe(
+    'export-star-overrides: OVERRIDDEN',
+  );
+  expect(object.extraData.exportStarSourceOnly).toBe(
+    'export-star-source: SOURCE_ONLY',
+  );
   expect(object).toMatchSnapshot();
   expect(cjs).toEqual(expect.objectContaining(cjs.default));
 

packages/metro/src/integration_tests/basic_bundle/import-export/export-star-overrides.js

@@ -0,0 +1,17 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @flow strict
+ */
+
+'use strict';
+
+export * from './export-star-source';
+
+export const overridden = 'export-star-overrides: OVERRIDDEN';
+
+export default 'export-star-overrides: DEFAULT';

packages/metro/src/integration_tests/basic_bundle/import-export/export-star-source.js

@@ -0,0 +1,17 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @flow strict
+ */
+
+'use strict';
+
+export default 'export-star-source: DEFAULT';
+
+export const overridden = 'export-star-source: OVERRIDDEN';
+
+export const sourceOnly = 'export-star-source: SOURCE_ONLY';

packages/metro/src/integration_tests/basic_bundle/import-export/index.js

@@ -25,6 +25,10 @@ import {foo} from './export-null';
 import primitiveDefault, {
   foo as primitiveFoo,
 } from './export-primitive-default';
+import exportStarDefault, {
+  overridden as exportStarOverridden,
+  sourceOnly as exportStarSourceOnly,
+} from './export-star-overrides';
 
 declare var require: RequireWithUnstableImportMaybeSync;
 
@@ -34,6 +38,9 @@ export {foo as default} from './export-4';
 export const extraData = {
   arrayFirst,
   arrayRest,
+  exportStarDefault,
+  exportStarOverridden,
+  exportStarSourceOnly,
   foo,
   importStar,
   myDefault,