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Fix type definitions for promises #10600

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merged 1 commit into from
Oct 6, 2020
Merged

Fix type definitions for promises #10600

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2 changes: 2 additions & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,8 @@

### Fixes

- `[jest-mock]` Fix typings for `mockResolvedValue`, `mockResolvedValueOnce`, `mockRejectedValue` and `mockRejectedValueOnce`

### Chore & Maintenance

### Performance
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22 changes: 12 additions & 10 deletions packages/jest-mock/src/index.ts
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Expand Up @@ -63,13 +63,15 @@ namespace JestMock {
mockReturnThis(): this;
mockReturnValue(value: T): this;
mockReturnValueOnce(value: T): this;
mockResolvedValue(value: T): this;
mockResolvedValueOnce(value: T): this;
mockRejectedValue(value: T): this;
mockRejectedValueOnce(value: T): this;
mockResolvedValue(value: Unpromisify<T>): this;
mockResolvedValueOnce(value: Unpromisify<T>): this;
mockRejectedValue(value: unknown): this;
mockRejectedValueOnce(value: unknown): this;
}
}

type Unpromisify<T> = T extends Promise<infer R> ? R : never;

/**
* Possible types of a MockFunctionResult.
* 'return': The call completed by returning normally.
Expand Down Expand Up @@ -661,20 +663,20 @@ class ModuleMockerClass {
// next function call will return this value or default return value
f.mockImplementationOnce(() => value);

f.mockResolvedValueOnce = (value: T) =>
f.mockImplementationOnce(() => Promise.resolve(value));
f.mockResolvedValueOnce = (value: Unpromisify<T>) =>
f.mockImplementationOnce(() => Promise.resolve(value as T));

f.mockRejectedValueOnce = (value: T) =>
f.mockRejectedValueOnce = (value: unknown) =>
f.mockImplementationOnce(() => Promise.reject(value));

f.mockReturnValue = (value: T) =>
// next function call will return specified return value or this one
f.mockImplementation(() => value);

f.mockResolvedValue = (value: T) =>
f.mockImplementation(() => Promise.resolve(value));
f.mockResolvedValue = (value: Unpromisify<T>) =>
f.mockImplementation(() => Promise.resolve(value as T));

f.mockRejectedValue = (value: T) =>
f.mockRejectedValue = (value: unknown) =>
f.mockImplementation(() => Promise.reject(value));

f.mockImplementationOnce = (
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21 changes: 21 additions & 0 deletions test-types/top-level-jest-namespace.test.ts
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Expand Up @@ -10,6 +10,7 @@
import {expectError, expectType} from 'mlh-tsd';
//eslint-disable-next-line import/no-extraneous-dependencies
import {jest} from '@jest/globals';
import type {Mock} from 'jest-mock';
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Ideally we'd allow access to this without having to explicitly go through jest-mock, but that's a problem for future us 🙂 For now this is a great improvement! 👍

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Yep, actually running into that in my own code as well, but unfortunately I don't know how to solve that...

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@SimenB SimenB Oct 6, 2020 •
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Yeah, solving that problem is a blocker for DefinitelyTyped/DefinitelyTyped#44365

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I wonder if just a @jest/utility-types would work, which re-export e.g. Mock, some pretty-format stuff for serializers, Config etc

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I don't have enough insight on the inner workings of Jest to have a valid opinion on that, but one challenge I am running into is that the Mock type from jest-mock (i.e. the type of the return value of jest.fn()) is different from the Mock type that's available as jest.Mock from @jest/globals, and it's not clear to me why. W.r.t. to importing it from jest-mock or from @jest/utility-types, either seems fine to me.

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import {jest} from '@jest/globals';
import jestMock = require('jest-mock');

jest.fn === jestMock.fn;

at least that's the intention. If that's not true, we've messed up somewhere 😅

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@Vinnl Vinnl Oct 6, 2020 •
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It doesn't seem to be true here: https://codesandbox.io/s/admiring-water-licv4?module=%2Fsrc%2Fjest.test.ts

Am I doing something wrong or should I report a bug?

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jest.Mock there comes from @types/jest not from the local jest import, so it's essentially what DefinitelyTyped/DefinitelyTyped#44365 is meant to solve

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Ah got it. Thanks!


expectType<void>(jest.addMatchers({}));
expectType<typeof jest>(jest.autoMockOff());
Expand Down Expand Up @@ -37,6 +38,26 @@ expectType<typeof jest>(jest.resetModuleRegistry());
expectType<typeof jest>(jest.resetModules());
expectType<typeof jest>(jest.isolateModules(() => {}));
expectType<typeof jest>(jest.retryTimes(3));
expectType<Mock<Promise<string>, []>>(
jest
.fn(() => Promise.resolve('string value'))
.mockResolvedValueOnce('A string, not a Promise'),
);
expectType<Mock<Promise<string>, []>>(
jest
.fn(() => Promise.resolve('string value'))
.mockResolvedValue('A string, not a Promise'),
);
expectType<Mock<Promise<string>, []>>(
jest
.fn(() => Promise.resolve('string value'))
.mockRejectedValueOnce(new Error('An error, not a string')),
);
expectType<Mock<Promise<string>, []>>(
jest
.fn(() => Promise.resolve('string value'))
.mockRejectedValue(new Error('An error, not a string')),
);

expectType<void>(jest.runAllImmediates());
expectType<void>(jest.runAllTicks());
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