cli: Fix handling of dynamic imports in esm.js files

Co-authored-by: Fredrik Adelöw <freben@gmail.com>
Co-authored-by: blam<ben@blam.sh>
Co-authored-by: Patrik Oldsberg <poldsberg@gmail.com>

packages/cli/config/jest.js

@@ -83,10 +83,8 @@ async function getConfig() {
       },
     },
 
-    // We build .esm.js files with plugin:build, so to be able to load these in tests they need to be transformed
-    // TODO: jest is working on module support, it's possible that we can remove this in the future
     transform: {
-      '\\.esm\\.js$': require.resolve('jest-esm-transformer'),
+      '\\.esm\\.js$': require.resolve('./jestEsmTransform.js'), // See jestEsmTransform.js
       '\\.(js|jsx|ts|tsx)$': require.resolve('ts-jest'),
       '\\.(bmp|gif|jpg|jpeg|png|frag|xml|svg)$': require.resolve(
         './jestFileTransform.js',

packages/cli/config/jestEsmTransform.js

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2020 Spotify AB
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const babel = require('@babel/core');
+
+// We build .esm.js files with plugin:build, so to be able to load these in tests they need to be transformed
+// TODO: jest is working on module support, it's possible that we can remove this in the future
+module.exports = {
+  process(src) {
+    const result = babel.transform(src, {
+      babelrc: false,
+      compact: false,
+      plugins: [
+        // This transforms the regular ESM syntax, import and export statements
+        require.resolve('@babel/plugin-transform-modules-commonjs'),
+        // This transforms dynamic `import()`, which is not supported yet in the Node.js VM API
+        require.resolve('babel-plugin-dynamic-import-node'),
+      ],
+    });
+
+    return result.code;
+  },
+};