[heft-jest-plugin] update to jest 27

[rzyns]

Summary

This updates the Jest dependency to the latest (~27.3.1) jest libraries.

Details

There are some breaking changes, which is to be expected when jumping two whole major versions. I'm not sure I've uncovered them all, the only one that seems to have affected the projects I've tested this on is disallowing done() callbacks in tests defined by asynchronous functions. I haven't measured performance quantitatively, but it feels like my builds are running faster with this change :)

How it was tested

• ran rush update && rush rebuild in a fresh clone
• proxied the package in my own Rush project of 27 packages (mix of browser and node), and ran rush update && rush rebuild many times to iteratively address the breaking changes in jest 27
• ran rush rebuild several times after addressing the breaking changes, and it consistently builds cleanly now

[ghost]

All CLA requirements met.

[ErikMikkelson]

Would it be worth updating jest-build-transform.ts to iterate over jestOptions.config.roots instead of hardcoding to package src? I have a modified version of the jest plugin for 27. which does that so we can keep our deployment code separate from our shipping code.

[rzyns]

Would it be worth updating jest-build-transform.ts to iterate over jestOptions.config.roots instead of hardcoding to package src? I have a modified version of the jest plugin for 27. which does that so we can keep our deployment code separate from our shipping code.

Yeah, that's a good idea, @ErikMikkelson. Maybe that should be done in a separate PR, though? At this point, I just really, really want modern Jest support in main-line Rush, so I figured I'd try to change as little as possible in this PR. But if you have a specific example of what you want to see and you're inclined to share it, please do send it my way. In either case, I'll poke around a bit more in jest-build-transform.ts and see what I can do

[ErikMikkelson]

Yeah, that's a good idea, @ErikMikkelson. Maybe that should be done in a separate PR, though?

You're right, @rzyns , I don't want to derail your PR. I can set up a PR later.

If you're curious, the code was in jest-build-transform, you just wrap the process with something like

// CHANGECHANGE: Looping through all jestOptions.roots instead of assuming 'src' for (const root of (jestOptions.config.roots || [])) { const [subdir] = root.split('/').slice(-1); // Is the input file under the "src" folder? const srcFolder: string = path.join(jestOptions.config.rootDir, subdir);

The only other place to change is the jest config, of course.

[D4N14L]

Hey @rzyns thanks for the PR! So I took some inspiration from this and created a separate PR with some additional changes. Feel free to take a look and try out this branch? #3076

[iclanton]

Jest 27 has been released with @rushstack/heft-jest-plugin@0.2.0