Update to Jest 24

[lorenzorapetti]

Things to notice before merging

• There's currently a bug for which jest 24 crashes if it's called programmatically. Until a bugfix comes out, i've added require('jest-cli/build/cli') before require('jest') like this comment suggests. This has been fixed in version 24.1 🎉

• The current version of jest-pnp-resolver doesn't work because jest changed the file names of jest-resolve. They already have the fix in their code but it isn't published yet. I've filed an issue, but in the meantime i've created pnpResolver.js just to make things work. Fixed in jest-pnp-resolver 1.1.0 🎉

• Jest 24 comes with a new setupFilesAfterEnv option that replaces setupTestFrameworkScriptFile. It now accepts an array of files instead of a single one. I'm wondering if we should allow multiple setup files?

[rally25rs]

I think (based on the comments in the issue) that jest@24 would fix #2393 so it would be really nice to get this working.

[marcoadkins]

Maybe rather than this here you modify the assignment of setupTestsFile above to potentially allow multiple files to be assigned:

function setupTestsFiles(rootDir) {
    const setupTestsFiles = [];
    if(fs.existsSync(paths.testsSetup)){
      const setupTestsMatches = paths.testsSetup.match(/src[/\\]setupTests\.(.+)/);
      const setupTestsFileExtension = (setupTestsMatches && setupTestsMatches[1]) || 'js';
      setupTestsFiles.push(`${rootDir}/src/setupTests.${setupTestsFileExtension}`)
    }
    return setupTestsFiles
}

...
module.exports = (resolve, rootDir, isEjecting) => {
...

setupFilesAfterEnv: setupTestsFiles(rootDir),

[lorenzorapetti]

I can totally do this, although i think that most users would use setupFilesAfterEnv like:

setupFilesAfterEnv: [
  'jest-dom/extend-expect',
  'react-testing-library/cleanup-after-each'
]

rather than creating multiple file themselves.

IMO we should allow overriding setupFilesAfterEnv in package.json if we really want to support this.

[SimenB]

Config for typescript can probably be simplified whenever this lands (jest uses babel-jest for ts automatically and finds tests). And if babel-core@bridge is only here for Jest, it can be removed

[mrmckeb]

Just a side-note/reminder: Once this is done we'll merge in #4176.

[lorenzorapetti]

I don't get why npx create-react-app --scripts-version=@latest test-app-dist-tag errors out with You have provided more than one argument for <project-directory>. in Travis 🤔

[iansu]

This is related to a recent change. I think if you swap the arguments it should work. Please try that and let us know if that doesn't resolve the issue.

[lorenzorapetti]

This is related to a recent change. I think if you swap the arguments it should work. Please try that and let us know if that doesn't resolve the issue.

It works now but there are 2 more failing builds that i can't get my head around. Can you help me with that? It appears that it fails only with latest node

[crubier]

This is super welcome for us, we want to start a monorepo project with CRA + Typescript + Jest, and we will not start until we get jest 24 working nicely with this dream stack :-)

[ianschmitz]

It works now but there are 2 more failing builds that i can't get my head around. Can you help me with that? It appears that it fails only with latest node

Yeah we're having some issues with the latest node builds in Travis on master as well.

[iansu]

Looks like we just have one failing test left: https://github.com/facebook/create-react-app/blob/master/test/fixtures/issue-5176-flow-class-properties/index.test.js

I'm not exactly sure why it's failing but let me know if you need any help looking into it.

[lorenzorapetti]

Looks like we just have one failing test left: /test/fixtures/issue-5176-flow-class-properties/index.test.js@master

I'm not exactly sure why it's failing but let me know if you need any help looking into it.

I'm not quite sure how to takle this, it passes in my local machine (i'm on node 10.15).

Right now i'm trying to debug what's happening on travis

[lorenzorapetti]

Aaaaand we have green lights 🎉🎉

[Domino987]

Awesome, when can we expect a release ?

[SimenB]

You should wait for jestjs/jest#8088

[crubier]

No, please please don't wait anymore lol, the pain is intense here without this merged, you have no idea!

I understand the problem with jestjs/jest#8088 , but this is a relatively rare bug that happens when you don't want to install watchman...

However having jest 24 (which supports typescript more easily) in create react app is a big deal for many of us.

[iansu]

We're going to merge this as is and release it in an alpha of version 3.0. I've created a follow up issue to make sure we update Jest before releasing the final version of 3.0.

[iansu]

@loryman The yarn.lock.cached file in react-scripts should not be part of your PR. Can you revert that file? Otherwise I think we're ready to merge this.

[lorenzorapetti]

@loryman The yarn.lock.cached file in react-scripts should not be part of your PR. Can you revert that file? Otherwise I think we're ready to merge this.

Yeah sorry, just reverted it!

[crubier]

We're going to merge this as is and release it in an alpha of version 3.0. I've created a follow up issue to make sure we update Jest before releasing the final version of 3.0.

Nice! Do you have an ETA on this v3 alpha release ? Thank you

[ianschmitz]

Nice! Do you have an ETA on this v3 alpha release ? Thank you

We're hoping in the next couple days to have a first cut alpha out.

[iansu]

Thanks!