feat(jest-util): add requireOrImportModule util for importing CJS or ESM

packages/jest-config/src/readConfigFileAndSetRootDir.ts

@@ -6,11 +6,10 @@
  */
 
 import * as path from 'path';
-import {pathToFileURL} from 'url';
 import * as fs from 'graceful-fs';
 import type {Register} from 'ts-node';
 import type {Config} from '@jest/types';
-import {interopRequireDefault} from 'jest-util';
+import {interopRequireDefault, requireOrImportModule} from 'jest-util';
 import {
   JEST_CONFIG_EXT_JSON,
   JEST_CONFIG_EXT_TS,
@@ -35,33 +34,10 @@ export default async function readConfigFileAndSetRootDir(
     if (isTS) {
       configObject = await loadTSConfigFile(configPath);
     } else {
-      configObject = require(configPath);
+      configObject = await requireOrImportModule<any>(configPath);
     }
   } catch (error) {
-    if (error.code === 'ERR_REQUIRE_ESM') {
-      try {
-        const configUrl = pathToFileURL(configPath);
-
-        // node `import()` supports URL, but TypeScript doesn't know that
-        const importedConfig = await import(configUrl.href);
-
-        if (!importedConfig.default) {
-          throw new Error(
-            `Jest: Failed to load mjs config file ${configPath} - did you use a default export?`,
-          );
-        }
-
-        configObject = importedConfig.default;
-      } catch (innerError) {
-        if (innerError.message === 'Not supported') {
-          throw new Error(
-            `Jest: Your version of Node does not support dynamic import - please enable it or use a .cjs file extension for file ${configPath}`,
-          );
-        }
-
-        throw innerError;
-      }
-    } else if (isJSON) {
+    if (isJSON) {
       throw new Error(
         `Jest: Failed to parse config file ${configPath}\n` +
           `  ${jsonlint.errors(fs.readFileSync(configPath, 'utf8'))}`,

packages/jest-transform/src/ScriptTransformer.ts

@@ -7,7 +7,6 @@
 
 import {createHash} from 'crypto';
 import * as path from 'path';
-import {pathToFileURL} from 'url';
 import {transformSync as babelTransform} from '@babel/core';
 // @ts-expect-error: should just be `require.resolve`, but the tests mess that up
 import babelPluginIstanbul from 'babel-plugin-istanbul';
@@ -23,6 +22,7 @@ import {
   createDirectory,
   interopRequireDefault,
   isPromise,
+  requireOrImportModule,
   tryRealpath,
 } from 'jest-util';
 import handlePotentialSyntaxError from './enhanceUnexpectedTokenMessage';
@@ -252,28 +252,9 @@ class ScriptTransformer {
     await Promise.all(
       this._config.transform.map(
         async ([, transformPath, transformerConfig]) => {
-          let transformer: Transformer;
-
-          try {
-            transformer = interopRequireDefault(require(transformPath)).default;
-          } catch (error) {
-            if (error.code === 'ERR_REQUIRE_ESM') {
-              const configUrl = pathToFileURL(transformPath);
-
-              // node `import()` supports URL, but TypeScript doesn't know that
-              const importedConfig = await import(configUrl.href);
-
-              if (!importedConfig.default) {
-                throw new Error(
-                  `Jest: Failed to load ESM transformer at ${transformPath} - did you use a default export?`,
-                );
-              }
-
-              transformer = importedConfig.default;
-            } else {
-              throw error;
-            }
-          }
+          let transformer: Transformer = await requireOrImportModule(
+            transformPath,
+          );
 
           if (!transformer) {
             throw new TypeError('Jest: a transform must export something.');

packages/jest-util/src/index.ts

@@ -23,3 +23,4 @@ export * as preRunMessage from './preRunMessage';
 export {default as pluralize} from './pluralize';
 export {default as formatTime} from './formatTime';
 export {default as tryRealpath} from './tryRealpath';
+export {default as requireOrImportModule} from './requireOrImportModule';

packages/jest-util/src/requireOrImportModule.ts

@@ -0,0 +1,50 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import {isAbsolute} from 'path';
+import {pathToFileURL} from 'url';
+import type {Config} from '@jest/types';
+import interopRequireDefault from './interopRequireDefault';
+
+export default async function requireOrImportModule<T>(
+  filePath: Config.Path,
+): Promise<T> {
+  let module: T;
+  if (!isAbsolute(filePath) && filePath[0] === '.') {
+    throw new Error(`Jest: requireOrImportModule path must be absolute`);
+  }
+  try {
+    module = interopRequireDefault(require(filePath)).default;
+  } catch (error) {
+    if (error.code === 'ERR_REQUIRE_ESM') {
+      try {
+        const configUrl = pathToFileURL(filePath);
+
+        // node `import()` supports URL, but TypeScript doesn't know that
+        const importedConfig = await import(configUrl.href);
+
+        if (!importedConfig.default) {
+          throw new Error(
+            `Jest: Failed to load ESM at ${filePath} - did you use a default export?`,
+          );
+        }
+
+        module = importedConfig.default;
+      } catch (innerError) {
+        if (innerError.message === 'Not supported') {
+          throw new Error(
+            `Jest: Your version of Node does not support dynamic import - please enable it or use a .cjs file extension for file ${filePath}`,
+          );
+        }
+        throw innerError;
+      }
+    } else {
+      throw error;
+    }
+  }
+  return module;
+}