fix global setup and teardown for jest multi-project setups

[ajwootto]

Fix the issue created by #389
Update the global setup and teardown to support having Jest "projects" specified. If specified, the preset will write a globalSetup.json file to each project directory, and remove all of them during teardown.

If the "projects" option is not in use, it will continue with the behaviour introduced in the above PR by writing a single globalSetup.json file to the rootDir.

This behaviour attempts to accommodate the use-case described in that PR without breaking the functionality for test setups using projects.

Edit:
Updated to instead use the globalConfig's "rootDir" field rather than the projectConfig in environment.ts. This field is set even when the projects option is in use. We only need to write one globalConfig.json file per Jest execution.

[Grmiade]

Thanks a lot @ajwootto for your help on this 👍 Just one remark.

[Grmiade]

config.projects can also be a list of sub-config. See https://jestjs.io/docs/configuration#projects-arraystring--projectconfig
We should probably have something like that:

Suggested change

	const projects = config.projects.length ? config.projects : [config.rootDir];
	const globalConfigPaths = projects.map(project => join(project, 'globalConfig.json'));
	const projects = config.projects.length ? config.projects : [config];
	const globalConfigPaths = projects.map(project.rootDir => join(project, 'globalConfig.json'));

What do you think?

[ajwootto]

@Grmiade looks like you are correct, if I set up a jest config using a combination of "string" projects and objects with project configuration, the setup function is called with that same array. I can definitely fix it for that, but I'm struggling with the type definition to use here. The Jest source shows this function being called with an object of type "GlobalConfig"
https://github.com/facebook/jest/blob/aae0d3ac3498ece4673ec29277dc040234f9f643/packages/jest-core/src/runGlobalHook.ts#L58

but that type only specifies projects as being an array of strings, which seems incorrect:
https://github.com/facebook/jest/blob/aae0d3ac3498ece4673ec29277dc040234f9f643/packages/jest-types/src/Config.ts#L392

it's defined correctly in "InitialOptions" but I don't think that represents the rest of what's passed in there correctly either...
https://github.com/facebook/jest/blob/aae0d3ac3498ece4673ec29277dc040234f9f643/packages/jest-types/src/Config.ts#L280

[ajwootto]

disregard all that, updated the PR to just use the globalConfig rootDir field (which is always set and works for both use-cases as well.)

[Grmiade]

Thanks 🙏

[harazdovskiy]

@ajwootto, thanks for contributing to jest-mongodb, your changes were published in v4.1.6!

[ajwootto]

thanks @harazdovskiy !