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feat(jest): add mocked property #57775

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feat(jest): add mocked property #57775

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2ba2c5b
feat(jest): add `mocked` property
G-Rath Dec 19, 2021
e615bc7
fix(jest): update version header
G-Rath Dec 19, 2021
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3 changes: 2 additions & 1 deletion types/jest/index.d.ts
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@@ -1,4 +1,4 @@
// Type definitions for Jest 27.0
// Type definitions for Jest 27.4
// Project: https://jestjs.io/
// Definitions by: Asana (https://asana.com)
// Ivo Stratev <https://github.com/NoHomey>
Expand Down Expand Up @@ -73,6 +73,7 @@ type ExtractEachCallbackArgs<T extends ReadonlyArray<any>> = {
];

declare namespace jest {
const mocked: typeof import('jest-mock').mocked;
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since we adding jest-mock dependency here
should we need to import all types/functions exported by jest-mock like this. No ?
so that it looks consistent :)
or it doesn't matter

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@G-Rath G-Rath Dec 19, 2021 •
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For now it doesn't matter as this is a new API whereas the existing types are slightly different from what's provided in jest-mock so need to be checked first and that's not as important as typing the new api.

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@SimenB SimenB Dec 20, 2021 •
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won't this break for people who have e.g.

function doSomething(jest.Mock<something, somethingElse>) {
}

doSomething(jest.mocked({}));

?

(Long term I want @types/jest to import all of its things from Jest itself (#44365), but as long as that's not the case, mixing seems less than ideal?)

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What you've provided isn't actually valid because jest.Mock is actually sort of poorly named jest.MockedFunction, where as jest.mocked({}) returns jest.MockedObject.

However no it won't because the types should all be compatible.

here's some code showcasing this 
import { mocked as tsJestMocked } from 'ts-jest/utils';
// import { jest } from '@jest/globals';
import * as MockTypes from 'jest-mock';
import * as jestMock from 'jest-mock';

// type MockTypes = jest;
// type MockTypes = typeof jestMock;
const mocked = jestMock.mocked;
// const mocked = jest.mocked;
// const mocked = tsJestMocked;

class Greeter {
  private readonly _greeting: string;

  public constructor(greeting: string) {
    this._greeting = greeting;
  }

  public get greeting() {
    return this._greeting;
  }

  public sayHello(target: string) {
    console.log(`${this._greeting} ${target}`);
  }
}

interface Point {
  x: string;
  y: number;
}

const makePoint = (x: string, y: number): Point => {
  return { x, y };
};

declare function doSomethingWithMockedFn(
  fn: jest.Mock<Point, [string, number]>
): void;
declare function doSomethingWithMockedMakePoint(
  fn: jest.Mocked<typeof makePoint>
): void;

declare function doSomethingWithMockedObject(fn: jest.Mocked<Point>): void;

declare function doSomethingWithMockedClass(
  fn: jest.MockedClass<typeof Greeter>
): void;

doSomethingWithMockedFn(mocked(makePoint));
doSomethingWithMockedMakePoint(mocked(makePoint));
doSomethingWithMockedObject(mocked({ x: '', y: 1 }));
doSomethingWithMockedClass(mocked(Greeter));

Regardless of what combination you use (e.g. types from jest-mocked + mocked from the jest global, everything from jest-mocked, everything from ts-jest, renaming the jest.<type> to be MockTypes.<type>, etc) the errors and passes are the same.

The first and last doSomething method calls have errors because of type issues (which basically boil down to the conditional typing of mocked resulting in a more accurate type than what's being used) while the middle two calls don't.

Long term I want @types/jest to import all of its things from Jest itself (#44365), but as long as that's not the case, mixing seems less than ideal?

That was part of my goal here, as we're already mixing types with jest-diff and pretty-format - but I didn't want to change the existing types in this PR because of the size of that work.

However looking at it with fresh eyes, it'll be a better IDE experience anyway to go with #57776 so let's do that.

https://github.com/DefinitelyTyped/DefinitelyTyped/pull/57776/files#r772003152

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(the problem with #57776 is it is mixing types too, but it's more subtle because they have slightly different names)

/**
* Disables automatic mocking in the module loader.
*/
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6 changes: 6 additions & 0 deletions types/jest/jest-tests.ts
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Expand Up @@ -1572,3 +1572,9 @@ test(`returns a Promise<any> and takes done`, (done) => {
test(`async function takes done`, async (done) => {
done();
});

// $ExpectError
jest.mocked();

// $ExpectType MockedObject<{}>
jest.mocked({});
1 change: 1 addition & 0 deletions types/jest/package.json
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Expand Up @@ -2,6 +2,7 @@
"private": true,
"dependencies": {
"jest-diff": "^27.0.0",
"jest-mock": "^27.4.0",
"pretty-format": "^27.0.0"
},
"exports": {
Expand Down