fix(custom-webpack): register ts-node only once (#1035)

* test(custom-webpack): add failing test for #1031

* fix(custom-webpack): actual fix for #1031

Closes #1031

packages/custom-webpack/src/transform-factories.spec.ts

@@ -0,0 +1,43 @@
+jest.mock('ts-node', () => ({
+  register: jest.fn(),
+}));
+jest.mock('tsconfig-paths', () => ({
+  loadConfig: jest.fn().mockReturnValue({}),
+}));
+import * as utils from './utils';
+jest.spyOn(utils, 'tsNodeRegister');
+
+import { getTransforms } from './transform-factories';
+
+describe('getTransforms', () => {
+  beforeEach(() => {
+    jest.resetModules();
+  });
+  it('should call ts-node register once with typescript index-html-transform & custom-webpack-config', () => {
+    jest.mock('test/index-transform.test.ts', () => jest.fn(), { virtual: true });
+    jest.mock('test/webpack.test.config.ts', () => jest.fn(), { virtual: true });
+    const tsNode = require('ts-node') as jest.Mocked<typeof import('ts-node')>;
+
+    const transforms = getTransforms(
+      {
+        customWebpackConfig: {
+          path: 'webpack.test.config.ts',
+        },
+        indexTransform: 'index-transform.test.ts',
+        tsConfig: 'tsconfig.test.json',
+      },
+      { workspaceRoot: './test' } as any
+    );
+    transforms.webpackConfiguration({});
+
+    expect(utils.tsNodeRegister).toHaveBeenCalledWith(
+      'test/webpack.test.config.ts',
+      'test/tsconfig.test.json'
+    );
+    expect(utils.tsNodeRegister).toHaveBeenCalledWith(
+      'index-transform.test.ts',
+      'test/tsconfig.test.json'
+    );
+    expect(tsNode.register).toHaveBeenCalledTimes(1);
+  });
+});

packages/custom-webpack/src/utils.ts

@@ -1,11 +1,16 @@
-/**
- * check for TS node registration
- * @param file: file name or file directory are allowed
- * @todo tsNodeRegistration: require ts-node if file extension is TypeScript
- */
-export function tsNodeRegister(file: string = '', tsConfig?: string) {
-  if (file && file.endsWith('.ts')) {
-    // Register TS compiler lazily
+const _tsNodeRegister = (() => {
+  let lastTsConfig: string | null | undefined;
+  return (tsConfig?: string) => {
+    // Check if the function was previously called with the same tsconfig
+    if (typeof lastTsConfig !== 'undefined' && (tsConfig ?? null) !== lastTsConfig) {
+      throw new Error('Called with multiple tsconfigs.');
+    }
+    if (lastTsConfig) {
+      return;
+    }
+    lastTsConfig = tsConfig ?? null;
+
+    // Register ts-node
     require('ts-node').register({
       project: tsConfig,
       compilerOptions: {
@@ -22,5 +27,17 @@ export function tsNodeRegister(file: string = '', tsConfig?: string) {
     if (baseUrl && paths) {
       tsconfigPaths.register({ baseUrl, paths });
     }
+  };
+})();
+
+/**
+ * check for TS node registration
+ * @param file: file name or file directory are allowed
+ * @todo tsNodeRegistration: require ts-node if file extension is TypeScript
+ */
+export function tsNodeRegister(file: string = '', tsConfig?: string) {
+  if (file && file.endsWith('.ts')) {
+    // Register TS compiler lazily
+    _tsNodeRegister(tsConfig);
   }
 }