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Importing jest returns undefined - TypeError: Cannot read property 'run' of undefined #8080

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blackdynamo opened this issue Mar 7, 2019 · 2 comments 路 Fixed by #8081
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@blackdynamo
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馃挜 Regression Report

The switch to use Typescript introduced a regression in a minor version change.

9fa3268#diff-153503da41d156755e19c0aedcd2eb43R10

The change is now throwing an error:

TypeError: Cannot read property 'run' of undefined

The actual default export of jest no longer has anything on it. Users now have to import the exact named exports. To work around the issue, you must now do this:

import * as jest from "jest";

console.log(jest);
console.log(jest.getVersion());

// or

import {getVersion} from "jest";

console.log(getVersion());

NOTE: This is specific you using ES6 import

Last working version

Worked up to version: 24.0.0 & 24.1.0

Stopped working in version: 24.3.0

To Reproduce

See included repo link below:

import jest from "jest";

console.log(jest);
console.log(jest.getVersion());

Expected behavior

Expected jest to be defined, but it's undefined.
Expected jest to look like this:

{ SearchSource: [Function: SearchSource],
  TestScheduler: [Function: TestScheduler],
  TestWatcher: [Function: TestWatcher],
  getVersion: [Function: getVersion],
  run: [Function: run],
  runCLI: [Function: runCLI] }

Link to repl or repo (highly encouraged)

https://github.com/blackdynamo/jest-24.3.0-import-regression

24.1.0 Working
image

24.3.0 Not Working
image

Run npx envinfo --preset jest

Paste the results here:

  System:
    OS: macOS 10.14.3
    CPU: (8) x64 Intel(R) Core(TM) i7-4980HQ CPU @ 2.80GHz
  Binaries:
    Node: 10.15.2 - ~/.nvm/versions/node/v10.15.2/bin/node
    npm: 6.4.1 - ~/.nvm/versions/node/v10.15.2/bin/npm
  npmPackages:
    jest: 24.3.0 => 24.3.0 
@SimenB
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SimenB commented Mar 7, 2019

Thanks for the report! I've opened up #8081 which fixes it.

However, I recommend you to do import {run} from 'jest' - it doesn't really have a default export. Also see #5048 for discussions about a programmatic API

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