Typing failure on expect().toThrow(Error) with explicit imports

[momocow]

🐛 Bug Report

Here's the minimum reproducible snippet.

My project is written in Typescript and I'm using jest along with ts-jest.

// test.ts
import { test, expect } from '@jest/globals'

test('error', () => {
  function throwError (): never { throw new Error() }
  expect(throwError).toThrow(Error)
})

After running the test file, an error is shown.

error TS2345: Argument of type 'ErrorConstructor' is not assignable to parameter of type 'string | RegExp | Error | Constructable | undefined'.
      Type 'ErrorConstructor' is not assignable to type 'Constructable'.
        Types of parameters 'message' and 'args' are incompatible.
          Type 'unknown' is not assignable to type 'string | undefined'.
            Type 'unknown' is not assignable to type 'string'.

However, if I remove the first line which makes the test using jest globals, everything works fine.

That is,

// test.ts
test('error', () => {
  function throwError (): never { throw new Error() }
  expect(throwError).toThrow(Error)
})

I found that source definition of expect is different between two tests.

With explicit imports, the definition is coming from node_modules\expect\build\types.d.ts, while with implicit imports, the definition is coming from node_modules\@types\jest\index.d.ts.

To Reproduce

Steps to reproduce the behavior:

• Create a test file with the snippet above.
• Run the test.

Expected behavior

No typing errors.

envinfo

  System:
    OS: Windows 10 10.0.18362
    CPU: (8) x64 Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz
  Binaries:
    Node: 12.16.0 - <Program Files>\nodejs\node.EXE
    Yarn: 1.9.4 - <Program Files>\Yarn\bin\yarn.CMD
    npm: 6.13.4 - <Program Files>\nodejs\npm.CMD
  npmPackages:
    jest: ^26.0.1 => 26.0.1

[josh-berry]

This is reproducible with just the expect package by itself. Here's how to setup a minimal test:

$ mkdir repro
$ cd repro
$ npm init
$ npm i --save-dev typescript expect
$ vi test.ts

Write the following into the test.ts file:

import expect from 'expect';

function oops() {
    throw new Error('oops');
}

expect(oops).toThrow(Error);

Then try to compile it with --strict --esModuleInterop (the latter option is needed to allow the use of import):

$ ./node_modules/.bin/tsc --strict --esModuleInterop test.ts

test.ts:7:22 - error TS2345: Argument of type 'ErrorConstructor' is not assignable to parameter of type 'string | RegExp | Error | Constructable | undefined'.
  Type 'ErrorConstructor' is not assignable to type 'Constructable'.
    Types of parameters 'message' and 'args' are incompatible.
      Type 'unknown' is not assignable to type 'string | undefined'.
        Type 'unknown' is not assignable to type 'string'.

7 expect(oops).toThrow(Error);
                       ~~~~~

  test.ts:7:22
    7 expect(oops).toThrow(Error);
                           ~~~~~
    Did you mean to use 'new' with this expression?


Found 1 error.

[SimenB]

PR welcome 🙂

[github-actions]

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