fix(jest): support more config file formats

[nicojs]

Support all config file formats for jest using jest's native config reading (including jest.config.ts). See https://jestjs.io/docs/configuration for a list of all available config formats.

Stryker only uses jest's native functionality if it finds jest@>=29.2, otherwise, it falls back on its custom config file reading algorithm.

This also adds support for exporting an async function from your jest config file even for jest@<29.2, because of added functionality in the custom config loading logic.

See jestjs/jest#13356

Fixes #3710
Fixes #3480
Fixes #3476

[nicojs]

There is a complication with this approach. It might result in this error:

Cannot read properties of undefined (reading 'testEnvironmentOptions') TypeError: Cannot read properties of undefined (reading 'testEnvironmentOptions')

For both running regular unit tests as running stryker-js.

This happens when a user installed jest@<=27. See https://stackoverflow.com/questions/72078160/jest-testenvironmentoptions-cannot-be-read.

This happens because jest-config@>29.3 is now a direct dependency of @stryker-mutator/jest-runner. It has jest-environment-node and jest-environment-jsdom listed as transient dependencies. This results in roughly this tree:

.
└── node_modules
    ├── @stryker-mutator
    │   └── jest-runner
    ├── jest@27
    │   └── node_modules
    │       └── jest-environment-node@27
    └── jest-environment-node@29.3

(or jest-environment-jsdom equivalent)

The way to solve this is actually not that big of a deal: install jest-environment-node@27 yourself (or jsdom equivalent). This results in the following tree:

.
└── node_modules
    ├── @stryker-mutator
    │   └── jest-runner
    │       └── node_modules
    │           └── jest-environment-node@29
    ├── jest
    │   └── node_modules
    └── jest-environment-node@27

I still like the solution proposed in this PR.

An alternative might be to use the preinstalled version of jest-config when jest@>29.3 is detected. The downsides of that are:

• ⛔ reading jest.config.ts and other formats won't be supported for jest@<29.3.
• ⛔ a more significant maintenance burden on us.

@jimCresswell @bmordue @chaouiyounes11 what would you guys prefer?

@SimenB feel free to pitch in as well 😅

[jimCresswell]

Thanks @nicojs !

The way to solve this is actually not that big of a deal: install jest-environment-node@27 yourself (or jsdom equivalent).

I prefer this solution as well, it is more transparent to the end user, and also gives them the opportunity to solve the problem by updating their dependencies.

I think the only caveat is that it needs to be well documented in a way that is easy to find with a quick search.

[SimenB]

I'd try to load jest-config via the jest installation (meaning "reading jest.config.ts and other formats won't be supported for jest@<29.3" which is fine I think? Just document it).

const {createRequire} = require('module');
const requireFromJest = createRequire(require.resolve('jest'));
const requireFromJestCli = createRequire(requireFromJest.resolve('jest-cli'));
const jestConfigFromJest = requireFromJestCli('jest-config');
// or  requireFromJestCli('jest-config/package.json'); if you wanna look at e.g. the exact version

---

We've talked about splitting out defaults from jest-config before, so that it can be used without also loading the envs etc.. Never got around to doing it, tho.

[nicojs]

Thanks, @SimonB, and @jimCresswell for the advice.

I'm tempted to go with @SimonB's approach, simply because it would save a lot of headaches for existing users. One big downside is that create-react-app users don't have the luxury of choosing when to update jest... 😑

[SimenB]

RN and Metro recently upgraded to Jest 29, so CRA might be able to as well 🙂 (assuming the holdup is Meta and not CRA itself).

EDIT: Seems like it's CRA 😛 facebook/create-react-app#12662

[jimCresswell]

Either way, I am very excited about being able to validate the unit tests in Next.js projects.

[nicojs]

I've implemented @SimenB 's suggestion. I also added custom support for exporting an async function from jest config, even when using older versions (implemented that while I was at it ;)).

[jimCresswell]

💥

[nicojs]

Released in v6.3 🎉
https://github.com/stryker-mutator/stryker-js/releases/tag/v6.3.0

[nicojs]

Thanks for all help and feedback everyone! ♥