fix(fixtures): prevent a fixture named "then" from being awaited

packages/playwright/src/worker/fixtureRunner.ts

@@ -228,7 +228,7 @@ export class FixtureRunner {
       throw firstError;
   }
 
-  async resolveParametersForFunction(fn: Function, testInfo: TestInfoImpl, autoFixtures: 'worker' | 'test' | 'all-hooks-only', runnable: RunnableDescription): Promise<object | null> {
+  async resolveParametersForFunction(fn: Function, testInfo: TestInfoImpl, autoFixtures: 'worker' | 'test' | 'all-hooks-only', runnable: RunnableDescription): Promise<{ result: object } | null> {
     const collector = new Set<FixtureRegistration>();
 
     // Collect automatic fixtures.
@@ -264,7 +264,8 @@ export class FixtureRunner {
         return null;
       params[name] = fixture.value;
     }
-    return params;
+    // Wrap in an object to avoid returning a thenable if a fixture is named 'then'.
+    return { result: params };
   }
 
   async resolveParametersAndRunFunction(fn: Function, testInfo: TestInfoImpl, autoFixtures: 'worker' | 'test' | 'all-hooks-only', runnable: RunnableDescription) {
@@ -273,7 +274,7 @@ export class FixtureRunner {
       // Do not run the function when fixture setup has already failed.
       return null;
     }
-    await testInfo._runWithTimeout(runnable, () => fn(params, testInfo));
+    await testInfo._runWithTimeout(runnable, () => fn(params.result, testInfo));
   }
 
   private async _setupFixtureForRegistration(registration: FixtureRegistration, testInfo: TestInfoImpl, runnable: RunnableDescription): Promise<Fixture> {

packages/playwright/src/worker/workerMain.ts

@@ -391,7 +391,10 @@ export class WorkerMain extends ProcessRunner {
         await this._runEachHooksForSuites(suites, 'beforeEach', testInfo);
 
         // Setup fixtures required by the test.
-        testFunctionParams = await this._fixtureRunner.resolveParametersForFunction(test.fn, testInfo, 'test', { type: 'test' });
+        const params = await this._fixtureRunner.resolveParametersForFunction(test.fn, testInfo, 'test', { type: 'test' });
+        if (params !== null)
+          testFunctionParams = params.result;
+
       });
 
       if (testFunctionParams === null) {

tests/playwright-test/fixtures.spec.ts

@@ -834,3 +834,19 @@ test('should error if use is not called', async ({ runInlineTest }) => {
   expect(result.failed).toBe(1);
   expect(result.output).toContain(`use() was not called in fixture "fixture"`);
 });
+
+test('should not treat fixtures as thenable promise', async ({ runInlineTest }) => {
+  const { results } = await runInlineTest({
+    'a.test.ts': `
+      import { test as base, expect } from '@playwright/test';
+      const test = base.extend({
+        then: async ({}, use) => await use(() => 'test-function'),
+      });
+
+      test('should not treat fixtures as thenable promise', async ({ then }) => {
+        expect(typeof then).toBe('function');
+      });
+    `,
+  });
+  expect(results[0].status).toBe('passed');
+});