feat: support exports in package.json

CHANGELOG.md

@@ -13,6 +13,7 @@
 - `[@jest/expect-utils]` New module exporting utils for `expect` ([#12323](https://github.com/facebook/jest/pull/12323))
 - `[jest-jasmine2, jest-runtime]` [**BREAKING**] Use `Symbol` to pass `jest.setTimeout` value instead of `jasmine` specific logic ([#12124](https://github.com/facebook/jest/pull/12124))
 - `[jest-jasmine2, jest-types]` [**BREAKING**] Move all `jasmine` specific types from `@jest/types` to its own package ([#12125](https://github.com/facebook/jest/pull/12125))
+- `[jest-resolver]` [**BREAKING**] Add support for `package.json` `exports` ([11961](https://github.com/facebook/jest/pull/11961))
 - `[jest-snapshot]` [**BREAKING**] Migrate to ESM ([#12342](https://github.com/facebook/jest/pull/12342))
 - `[jest-worker]` [**BREAKING**] Allow only absolute `workerPath` ([#12343](https://github.com/facebook/jest/pull/12343))
 

examples/angular/jest.config.js

@@ -1,7 +1,7 @@
 module.exports = {
   moduleFileExtensions: ['ts', 'html', 'js', 'json'],
   setupFilesAfterEnv: ['<rootDir>/setupJest.js'],
-  testEnvironment: 'jsdom',
+  testEnvironment: '<rootDir>/test-env.js',
   transform: {
     '\\.[tj]s$': ['babel-jest', {configFile: require.resolve('./.babelrc')}],
   },

examples/angular/test-env.js

@@ -0,0 +1,13 @@
+'use strict';
+
+const {
+  TestEnvironment: JSDOMTestEnvironment,
+} = require('jest-environment-jsdom');
+
+module.exports = class AngularEnv extends JSDOMTestEnvironment {
+  exportConditions() {
+    // we need to include `node` as `rxjs` defines `node`, `es2015`, `default`, not `browser` or `require`
+    // https://github.com/ReactiveX/rxjs/pull/6821
+    return super.exportConditions().concat('node');
+  }
+};

packages/jest-resolve/src/__tests__/resolve.test.ts

@@ -160,24 +160,78 @@ describe('findNodeModule', () => {
     });
 
     test('resolves with import', () => {
-      const result = Resolver.findNodeModule('import', {
+      const result = Resolver.findNodeModule('exports', {
         basedir: conditionsRoot,
         conditions: ['import'],
       });
 
       expect(result).toEqual(
-        path.resolve(conditionsRoot, './node_modules/import/file.js'),
+        path.resolve(conditionsRoot, './node_modules/exports/import.js'),
       );
     });
 
     test('resolves with require', () => {
-      const result = Resolver.findNodeModule('require', {
+      const result = Resolver.findNodeModule('exports', {
         basedir: conditionsRoot,
         conditions: ['require'],
       });
 
       expect(result).toEqual(
-        path.resolve(conditionsRoot, './node_modules/require/file.js'),
+        path.resolve(conditionsRoot, './node_modules/exports/require.js'),
+      );
+    });
+
+    test('gets default when nothing is passed', () => {
+      const result = Resolver.findNodeModule('exports', {
+        basedir: conditionsRoot,
+        conditions: [],
+      });
+
+      expect(result).toEqual(
+        path.resolve(conditionsRoot, './node_modules/exports/default.js'),
+      );
+    });
+
+    test('respects order in package.json, not conditions', () => {
+      const resultImport = Resolver.findNodeModule('exports', {
+        basedir: conditionsRoot,
+        conditions: ['import', 'require'],
+      });
+      const resultRequire = Resolver.findNodeModule('exports', {
+        basedir: conditionsRoot,
+        conditions: ['require', 'import'],
+      });
+
+      expect(resultImport).toEqual(resultRequire);
+    });
+
+    test('supports nested paths', () => {
+      const result = Resolver.findNodeModule('exports/nested', {
+        basedir: conditionsRoot,
+        conditions: [],
+      });
+
+      expect(result).toEqual(
+        path.resolve(conditionsRoot, './node_modules/exports/nestedDefault.js'),
+      );
+    });
+
+    test('supports nested conditions', () => {
+      const resultRequire = Resolver.findNodeModule('exports/deeplyNested', {
+        basedir: conditionsRoot,
+        conditions: ['require'],
+      });
+      const resultDefault = Resolver.findNodeModule('exports/deeplyNested', {
+        basedir: conditionsRoot,
+        conditions: [],
+      });
+
+      expect(resultRequire).toEqual(
+        path.resolve(conditionsRoot, './node_modules/exports/nestedRequire.js'),
+      );
+
+      expect(resultDefault).toEqual(
+        path.resolve(conditionsRoot, './node_modules/exports/nestedDefault.js'),
       );
     });
   });
@@ -251,8 +305,8 @@ describe('resolveModule', () => {
     const src = require.resolve('../');
     const resolved = resolver.resolveModule(src, 'mockJsDependency', {
       paths: [
-        path.resolve(__dirname, '../../src/__tests__'),
         path.resolve(__dirname, '../../src/__mocks__'),
+        path.resolve(__dirname, '../../src/__tests__'),
       ],
     });
     expect(resolved).toBe(require.resolve('../__mocks__/mockJsDependency.js'));

packages/jest-resolve/src/defaultResolver.ts

@@ -5,13 +5,14 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-import {resolve} from 'path';
+import {isAbsolute} from 'path';
 import pnpResolver from 'jest-pnp-resolver';
 import {sync as resolveSync} from 'resolve';
 import {
   Options as ResolveExportsOptions,
   resolve as resolveExports,
 } from 'resolve.exports';
+import slash = require('slash');
 import type {Config} from '@jest/types';
 import {
   PkgJson,
@@ -59,10 +60,8 @@ export default function defaultResolver(
     ...options,
     isDirectory,
     isFile,
-    packageFilter: createPackageFilter(
-      options.conditions,
-      options.packageFilter,
-    ),
+    packageFilter: createPackageFilter(path, options.packageFilter),
+    pathFilter: createPathFilter(path, options.conditions, options.pathFilter),
     preserveSymlinks: false,
     readPackageSync,
     realpathSync,
@@ -82,45 +81,68 @@ function readPackageSync(_: unknown, file: Config.Path): PkgJson {
 }
 
 function createPackageFilter(
-  conditions?: Array<string>,
+  originalPath: Config.Path,
   userFilter?: ResolverOptions['packageFilter'],
 ): ResolverOptions['packageFilter'] {
-  function attemptExportsFallback(pkg: PkgJson) {
-    const options: ResolveExportsOptions = conditions
-      ? {conditions, unsafe: true}
-      : // no conditions were passed - let's assume this is Jest internal and it should be `require`
-        {browser: false, require: true};
-
-    try {
-      return resolveExports(pkg, '.', options);
-    } catch {
-      return undefined;
-    }
+  if (shouldIgnoreRequestForExports(originalPath)) {
+    return userFilter;
   }
 
-  return function packageFilter(pkg, packageDir) {
+  return function packageFilter(pkg, ...rest) {
     let filteredPkg = pkg;
 
     if (userFilter) {
-      filteredPkg = userFilter(filteredPkg, packageDir);
-    }
-
-    if (filteredPkg.main != null) {
-      return filteredPkg;
+      filteredPkg = userFilter(filteredPkg, ...rest);
     }
 
-    const indexInRoot = resolve(packageDir, './index.js');
-
-    // if the module contains an `index.js` file in root, `resolve` will request
-    // that if there is no `main`. Since we don't wanna break that, add this
-    // check
-    if (isFile(indexInRoot)) {
+    if (filteredPkg.exports == null) {
       return filteredPkg;
     }
 
     return {
       ...filteredPkg,
-      main: attemptExportsFallback(filteredPkg),
+      // remove `main` so `resolve` doesn't look at it and confuse the `.`
+      // loading in `pathFilter`
+      main: undefined,
     };
   };
 }
+
+function createPathFilter(
+  originalPath: Config.Path,
+  conditions?: Array<string>,
+  userFilter?: ResolverOptions['pathFilter'],
+): ResolverOptions['pathFilter'] {
+  if (shouldIgnoreRequestForExports(originalPath)) {
+    return userFilter;
+  }
+
+  const options: ResolveExportsOptions = conditions
+    ? {conditions, unsafe: true}
+    : // no conditions were passed - let's assume this is Jest internal and it should be `require`
+      {browser: false, require: true};
+
+  return function pathFilter(pkg, path, relativePath, ...rest) {
+    let pathToUse = relativePath;
+
+    if (userFilter) {
+      pathToUse = userFilter(pkg, path, relativePath, ...rest);
+    }
+
+    if (pkg.exports == null) {
+      return pathToUse;
+    }
+
+    // this `index` thing can backfire, but `resolve` adds it: https://github.com/browserify/resolve/blob/f1b51848ecb7f56f77bfb823511d032489a13eab/lib/sync.js#L192
+    const isRootRequire =
+      pathToUse === 'index' && !originalPath.endsWith('/index');
+
+    const newPath = isRootRequire ? '.' : slash(pathToUse);
+
+    return resolveExports(pkg, newPath, options) || pathToUse;
+  };
+}
+
+// if it's a relative import or an absolute path, exports are ignored
+const shouldIgnoreRequestForExports = (path: Config.Path) =>
+  path.startsWith('.') || isAbsolute(path);

packages/jest-runtime/src/__tests__/NODE_PATH_dir/package.json

@@ -0,0 +1,6 @@
+{
+  "name": "NODE_PATH_dir",
+  "version": "1.0.0",
+  "dependencies": {
+  }
+}

packages/jest-runtime/src/__tests__/test_root/package.json

@@ -0,0 +1,6 @@
+{
+  "name": "test_root",
+  "version": "1.0.0",
+  "dependencies": {
+  }
+}

packages/jest-runtime/src/index.ts

@@ -754,7 +754,7 @@ export default class Runtime {
       this._virtualMocks,
       from,
       moduleName,
-      isInternal ? undefined : {conditions: this.cjsConditions},
+      {conditions: this.cjsConditions},
     );
     let modulePath: string | undefined;
 
@@ -782,11 +782,9 @@ export default class Runtime {
     }
 
     if (!modulePath) {
-      modulePath = this._resolveModule(
-        from,
-        moduleName,
-        isInternal ? undefined : {conditions: this.cjsConditions},
-      );
+      modulePath = this._resolveModule(from, moduleName, {
+        conditions: this.cjsConditions,
+      });
     }
 
     if (this.unstable_shouldLoadAsEsm(modulePath)) {