chore: add support private methods in TS (#12051)

packages/playwright-test/src/transform.ts

@@ -158,6 +158,7 @@ export function transformHook(code: string, filename: string, isModule = false):
         [require.resolve('@babel/plugin-proposal-logical-assignment-operators')],
         [require.resolve('@babel/plugin-proposal-nullish-coalescing-operator')],
         [require.resolve('@babel/plugin-proposal-optional-chaining')],
+        [require.resolve('@babel/plugin-proposal-private-methods')],
         [require.resolve('@babel/plugin-syntax-json-strings')],
         [require.resolve('@babel/plugin-syntax-optional-catch-binding')],
         [require.resolve('@babel/plugin-syntax-async-generators')],

tests/playwright-test/babel.spec.ts

@@ -0,0 +1,38 @@
+/**
+ * Copyright (c) Microsoft Corporation.
+ *
+ * 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.
+ */
+
+import { test, expect } from './playwright-test-fixtures';
+
+test('should succeed', async ({ runInlineTest }) => {
+  const result = await runInlineTest({
+    'one-success.spec.ts': `
+      const { test } = pwt;
+
+      class Foo {
+        #logger = 2;
+        get #log() { return this.#logger; }
+        value() { return this.#log; };
+      }
+
+      test('succeeds', () => {
+        expect(new Foo().value()).toBe(2);
+      });
+    `
+  });
+  expect(result.exitCode).toBe(0);
+  expect(result.passed).toBe(1);
+  expect(result.failed).toBe(0);
+});