feat: support . in exports field

e2e/resolve-conditions/resolver.js

@@ -25,10 +25,10 @@ function createPathFilter(conditions) {
 
     return (
       resolveExports(pkg, path, {
-        // `resolve.exports adds `node` unless `browser` is `false`, so let's add this ugly thing
+        // `resolve.exports` adds `node` unless `browser` is `true`, so let's add this ugly thing
         browser: conditions.includes('browser'),
         conditions,
-        // `resolve.exports adds `import` unless `require` is `false`, so let's add this ugly thing
+        // `resolve.exports` adds `import` unless `require` is `true`, so let's add this ugly thing
         require: conditions.includes('require'),
       }) || relativePath
     );

packages/jest-resolve/package.json

@@ -23,6 +23,7 @@
     "jest-util": "^27.2.4",
     "jest-validate": "^27.2.4",
     "resolve": "^1.20.0",
+    "resolve.exports": "^1.0.2",
     "slash": "^3.0.0"
   },
   "devDependencies": {

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

@@ -146,6 +146,43 @@ describe('findNodeModule', () => {
       }),
     );
   });
+
+  describe('conditions', () => {
+    const conditionsRoot = path.resolve(__dirname, '../__mocks__/conditions');
+
+    test('resolves without exports, just main', () => {
+      const result = Resolver.findNodeModule('main', {
+        basedir: conditionsRoot,
+        conditions: ['require'],
+      });
+
+      expect(result).toEqual(
+        path.resolve(conditionsRoot, './node_modules/main/file.js'),
+      );
+    });
+
+    test('resolves with import', () => {
+      const result = Resolver.findNodeModule('import', {
+        basedir: conditionsRoot,
+        conditions: ['import'],
+      });
+
+      expect(result).toEqual(
+        path.resolve(conditionsRoot, './node_modules/import/file.js'),
+      );
+    });
+
+    test('resolves with require', () => {
+      const result = Resolver.findNodeModule('require', {
+        basedir: conditionsRoot,
+        conditions: ['require'],
+      });
+
+      expect(result).toEqual(
+        path.resolve(conditionsRoot, './node_modules/require/file.js'),
+      );
+    });
+  });
 });
 
 describe('resolveModule', () => {

packages/jest-resolve/src/defaultResolver.ts

@@ -8,6 +8,10 @@
 import * as fs from 'graceful-fs';
 import pnpResolver from 'jest-pnp-resolver';
 import {Opts as ResolveOpts, sync as resolveSync} from 'resolve';
+import {
+  Options as ResolveExportsOptions,
+  resolve as resolveExports,
+} from 'resolve.exports';
 import type {Config} from '@jest/types';
 import {tryRealpath} from 'jest-util';
 
@@ -43,6 +47,8 @@ export default function defaultResolver(
     ...options,
     isDirectory,
     isFile,
+    packageFilter:
+      options.packageFilter ?? createPackageFilter(options.conditions),
     preserveSymlinks: false,
     readPackageSync,
     realpathSync,
@@ -149,3 +155,31 @@ function realpathSync(file: Config.Path): Config.Path {
 function readPackageSync(_: unknown, file: Config.Path): PkgJson {
   return readPackageCached(file);
 }
+
+function createPackageFilter(conditions?: Array<string>) {
+  const options: ResolveExportsOptions = conditions
+    ? {
+        // `resolve.exports` adds `node` unless `browser` is `true`, so let's add this ugly thing
+        browser: conditions.includes('browser'),
+        conditions,
+        // `resolve.exports` adds `import` unless `require` is `true`, so let's add this ugly thing
+        require: conditions.includes('require'),
+      }
+    : // no conditions were passed - let's assume this is Jest internal and it should be `require`
+      {browser: false, require: true};
+
+  function attemptExportsFallback(pkg: PkgJson) {
+    try {
+      return resolveExports(pkg, '.', options);
+    } catch {
+      return undefined;
+    }
+  }
+
+  return function packageFilter(pkg: PkgJson) {
+    return {
+      ...pkg,
+      main: pkg.main ?? attemptExportsFallback(pkg),
+    };
+  };
+}

yarn.lock

@@ -13026,6 +13026,7 @@ fsevents@^1.2.7:
     jest-util: ^27.2.4
     jest-validate: ^27.2.4
     resolve: ^1.20.0
+    resolve.exports: ^1.0.2
     slash: ^3.0.0
   languageName: unknown
   linkType: soft
@@ -18944,6 +18945,13 @@ react-native@0.64.0:
   languageName: node
   linkType: hard
 
+"resolve.exports@npm:^1.0.2":
+  version: 1.0.2
+  resolution: "resolve.exports@npm:1.0.2"
+  checksum: 012a46e3ae41c53762abf5b50ea1b4adf2de617bbea1dbc7bf6e609c1ceaedee7782acbc92d443951d5dd0c3a8fb1090ce73285a9ccc24b530e33b5e09ae196f
+  languageName: node
+  linkType: hard
+
 "resolve@^1.1.6, resolve@^1.10.0, resolve@^1.14.2, resolve@^1.15.0, resolve@^1.19.0, resolve@^1.20.0, resolve@^1.3.2":
   version: 1.20.0
   resolution: "resolve@npm:1.20.0"