From 3d895067047176b01a2cca78b4c243dadad162d0 Mon Sep 17 00:00:00 2001
From: Dmitry Gozman <dgozman@gmail.com>
Date: Thu, 28 Jul 2022 12:57:05 -0700
Subject: [PATCH] fix(fixtures): make undefined option mean "default value"
 (#16026)

In the following example, `locale` inside the `describe`
would be reverted to the default value:

```js
test.use({ locale: 'en-GB' });

test.decsribe(() => {
  test.use({ locale: undefined });
});
```
---
 packages/playwright-test/src/fixtures.ts  | 11 +++++-
 tests/playwright-test/test-extend.spec.ts | 46 +++++++++++++++--------
 2 files changed, 40 insertions(+), 17 deletions(-)

diff --git a/packages/playwright-test/src/fixtures.ts b/packages/playwright-test/src/fixtures.ts
index a3b1d8f1cc..32f4410d8b 100644
--- a/packages/playwright-test/src/fixtures.ts
+++ b/packages/playwright-test/src/fixtures.ts
@@ -203,7 +203,7 @@ export class FixturePool {
           };
           value = value[0];
         }
-        const fn = value as (Function | any);
+        let fn = value as (Function | any);
 
         const previous = this.registrations.get(name);
         if (previous && options) {
@@ -222,6 +222,15 @@ export class FixturePool {
         if (options.scope === 'worker' && disallowWorkerFixtures)
           throw errorWithLocations(`Cannot use({ ${name} }) in a describe group, because it forces a new worker.\nMake it top-level in the test file or put in the configuration file.`, { location, name });
 
+        // Overriding option with "undefined" value means setting it to the default value
+        // from the original declaration of the option.
+        if (fn === undefined && options.option && previous) {
+          let original = previous;
+          while (original.super)
+            original = original.super;
+          fn = original.fn;
+        }
+
         const deps = fixtureParameterNames(fn, location);
         const registration: FixtureRegistration = { id: '', name, location, scope: options.scope, fn, auto: options.auto, option: options.option, timeout: options.timeout, customTitle: options.customTitle, deps, super: previous };
         registrationId(registration);
diff --git a/tests/playwright-test/test-extend.spec.ts b/tests/playwright-test/test-extend.spec.ts
index ab385337dd..8fd3b0af5a 100644
--- a/tests/playwright-test/test-extend.spec.ts
+++ b/tests/playwright-test/test-extend.spec.ts
@@ -230,35 +230,49 @@ test('test.use() with undefined should not be ignored', async ({ runInlineTest }
   const result = await runInlineTest({
     'playwright.config.ts': `
       module.exports = {
-        use: { option: 'config' },
+        use: { option1: 'config' },
       };
     `,
     'a.test.js': `
-      const test = pwt.test.extend({ option: [ 'default', { option: true } ] });
-      test('test1', async ({ option }) => {
-        console.log('test1-' + option);
+      const test = pwt.test.extend({
+        option1: [ 'default', { option: true } ],
+        option2: [ 'default', { option: true } ],
       });
+      test('test1', async ({ option1, option2 }) => {
+        console.log('test1: option1=' + option1);
+        console.log('test1: option2=' + option2);
+      });
+
       test.describe('', () => {
-        test.use({ option: 'foo' });
-        test('test2', async ({ option }) => {
-          console.log('test2-' + option);
+        test.use({ option1: 'foo', option2: 'foo' });
+        test('test2', async ({ option1, option2 }) => {
+          console.log('test2: option1=' + option1);
+          console.log('test2: option2=' + option2);
         });
+
         test.describe('', () => {
-          test.use({ option: undefined });
-          test('test3', async ({ option }) => {
-            console.log('test3-' + option);
+          test.use({ option1: undefined, option2: undefined });
+          test('test3', async ({ option1, option2 }) => {
+            console.log('test3: option1=' + option1);
+            console.log('test3: option2=' + option2);
           });
         });
       });
-      test.extend({ option: undefined })('test4', async ({ option }) => {
-        console.log('test4-' + option);
+
+      test.extend({ option1: undefined, option2: undefined })('test4', async ({ option1, option2 }) => {
+        console.log('test4: option1=' + option1);
+        console.log('test4: option2=' + option2);
       });
     `,
   });
   expect(result.exitCode).toBe(0);
   expect(result.passed).toBe(4);
-  expect(result.output).toContain('test1-config');
-  expect(result.output).toContain('test2-foo');
-  expect(result.output).toContain('test3-undefined');
-  expect(result.output).toContain('test4-undefined');
+  expect(result.output).toContain('test1: option1=config');
+  expect(result.output).toContain('test1: option2=default');
+  expect(result.output).toContain('test2: option1=foo');
+  expect(result.output).toContain('test2: option2=foo');
+  expect(result.output).toContain('test3: option1=config');
+  expect(result.output).toContain('test3: option2=default');
+  expect(result.output).toContain('test4: option1=config');
+  expect(result.output).toContain('test4: option2=default');
 });