[jest-expo] expo's jest-preset is called twice, leading to warnings in console and a corrupted jest-preset

[alex-fournier]

🐛 Bug Report

Summary of Issue (just a few sentences)

Since upgraded to Expo SDK 38, I noticed some warnings in console when executing jest. The jest-preset.js file in jest-expo is called twice, it is due to a change since jest@25.

The preset is built by mutating the react-native preset, leading to warnings on the second pass and a corrupted output. The preset should be built in a immutable way.

Environment - output of expo diagnostics & the platform(s) you're targeting

  Expo CLI 3.21.13 environment info:
    System:
      OS: Windows 10 10.0.19041
    Binaries:
      Node: 12.16.1 - D:\Programs\nodejs\node.EXE
      Yarn: 1.22.4 - D:\Programs\Yarn\bin\yarn.CMD
      npm: 6.13.4 - D:\Programs\nodejs\npm.CMD
    npmPackages:
      expo: ^38.0.0 => 38.0.8
      react: 16.11.0 => 16.11.0
      react-native: https://github.com/expo/react-native/archive/sdk-38.0.0.tar.gz => 0.62.2

Reproducible Demo

1. expo init -t tabs jest-demo
2. cd jest-demo
3. yarn test

Warnings showing in console:

Expected react-native/jest-preset to define transform[^.+\.(bmp|gif|jpg|jpeg|mp4|png|psd|svg|webp)$]
react-native/jest-preset contained different transformIgnorePatterns than expected

Workaround

1. yarn add jest@^24.0.0
2. Launch tests using this command: node ./node_modules/jest/bin.jest.js

[byCedric]

Hi @alex-fournier! Thanks for the issue report and a PR 😄 Do you know what change could cause this? I went over the changelog for 25.x.x, but I can't find anything that might have affected this.

[alex-fournier]

I think this commit is causing the issue : jestjs/jest#8894

Fix Jest multi project runner still cannot handle exactly one project in the CHANGELOG of 25.1.0.

[brunohkbx]

+1
This change here introduced the issue:
https://github.com/facebook/jest/pull/8894/files#diff-9787071c48fc2896fbe36394532b7288R294

[alex-fournier]

Any news on this? The PR is ready but still not merged.

[renanmav]

@alex-fournier I can confirm that it works for me (patched jest-expo here)