From 0ab4a345d0302647ece2f5409fdd7b7a50ee306c Mon Sep 17 00:00:00 2001
From: Dmitry Gozman <dgozman@gmail.com>
Date: Fri, 24 Sep 2021 12:51:40 -0700
Subject: [PATCH] feat(test runner): improve fixture typings for function
 fixtures

When fixture value `R` is a function, TypeScript sometimes confuses
function `R` and function `async ({}, use) => {}`. This leads to
`any` types in the latter because it could be either of the functions
as TS thinks.

The solution is to only accept the second syntax, assuming that noone
passes fixture value that is a function as is:

```js
// This will stop working.
test.extend<{ foo: (x: number) => number }>({
  foo: x => 2 * x,
});

// This will get inferred types and autocomplete.
test.extend<{ foo: (x: number) => number }>({
  foo: async ({}, use) => {
    await use(x => 2 * x);
  },
});
```
---
 tests/playwright-test/types.spec.ts      | 12 ++++++++++++
 types/test.d.ts                          |  4 ++--
 utils/generate_types/overrides-test.d.ts |  4 ++--
 3 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/tests/playwright-test/types.spec.ts b/tests/playwright-test/types.spec.ts
index 234eb9b23b764..91329580c4e65 100644
--- a/tests/playwright-test/types.spec.ts
+++ b/tests/playwright-test/types.spec.ts
@@ -82,6 +82,18 @@ test('should check types of fixtures', async ({runTSC}) => {
         // @ts-expect-error
         }, { scope: 'test' } ],
       });
+
+      type AssertNotAny<S> = {notRealProperty: number} extends S ? false : true;
+      type AssertType<T, S> = S extends T ? AssertNotAny<S> : false;
+      const funcTest = pwt.test.extend<{ foo: (x: number, y: string) => Promise<string> }>({
+        foo: async ({}, use) => {
+          await use(async (x, y) => {
+            const assertionX: AssertType<number, typeof x> = true;
+            const assertionY: AssertType<string, typeof y> = true;
+            return y;
+          });
+        },
+      })
     `,
     'playwright.config.ts': `
       import { MyOptions } from './helper';
diff --git a/types/test.d.ts b/types/test.d.ts
index 8375c4f8e3077..708087b0d48a8 100644
--- a/types/test.d.ts
+++ b/types/test.d.ts
@@ -2282,8 +2282,8 @@ export interface TestType<TestArgs extends KeyValue, WorkerArgs extends KeyValue
 type KeyValue = { [key: string]: any };
 export type TestFixture<R, Args extends KeyValue> = (args: Args, use: (r: R) => Promise<void>, testInfo: TestInfo) => any;
 export type WorkerFixture<R, Args extends KeyValue> = (args: Args, use: (r: R) => Promise<void>, workerInfo: WorkerInfo) => any;
-type TestFixtureValue<R, Args> = R | TestFixture<R, Args>;
-type WorkerFixtureValue<R, Args> = R | WorkerFixture<R, Args>;
+type TestFixtureValue<R, Args> = Exclude<R, Function> | TestFixture<R, Args>;
+type WorkerFixtureValue<R, Args> = Exclude<R, Function> | WorkerFixture<R, Args>;
 export type Fixtures<T extends KeyValue = {}, W extends KeyValue = {}, PT extends KeyValue = {}, PW extends KeyValue = {}> = {
   [K in keyof PW]?: WorkerFixtureValue<PW[K], W & PW> | [WorkerFixtureValue<PW[K], W & PW>, { scope: 'worker' }];
 } & {
diff --git a/utils/generate_types/overrides-test.d.ts b/utils/generate_types/overrides-test.d.ts
index 0dc3004bd10d0..48f9c0074c2d7 100644
--- a/utils/generate_types/overrides-test.d.ts
+++ b/utils/generate_types/overrides-test.d.ts
@@ -265,8 +265,8 @@ export interface TestType<TestArgs extends KeyValue, WorkerArgs extends KeyValue
 type KeyValue = { [key: string]: any };
 export type TestFixture<R, Args extends KeyValue> = (args: Args, use: (r: R) => Promise<void>, testInfo: TestInfo) => any;
 export type WorkerFixture<R, Args extends KeyValue> = (args: Args, use: (r: R) => Promise<void>, workerInfo: WorkerInfo) => any;
-type TestFixtureValue<R, Args> = R | TestFixture<R, Args>;
-type WorkerFixtureValue<R, Args> = R | WorkerFixture<R, Args>;
+type TestFixtureValue<R, Args> = Exclude<R, Function> | TestFixture<R, Args>;
+type WorkerFixtureValue<R, Args> = Exclude<R, Function> | WorkerFixture<R, Args>;
 export type Fixtures<T extends KeyValue = {}, W extends KeyValue = {}, PT extends KeyValue = {}, PW extends KeyValue = {}> = {
   [K in keyof PW]?: WorkerFixtureValue<PW[K], W & PW> | [WorkerFixtureValue<PW[K], W & PW>, { scope: 'worker' }];
 } & {