feat(typescript-estree): add maximumDefaultProjectFileMatchCount and wide allowDefaultProjectForFiles glob restrictions

[JoshuaKGoldberg]

PR Checklist

• Addresses an existing open issue: fixes Enhancement: ban wide globs in parserOptions.useProjectService.allowDefaultProjectForFiles #8923
• That issue was marked as accepting prs
• Steps in Contributing were taken

Overview

Adds the two safety checks for allowDefaultProjectForFiles as suggested in the issue:

• A new maximumDefaultProjectFileMatchCount_THIS_WILL_SLOW_DOWN_LINTING option with a default value of 8
• A check that allowDefaultProjectForFiles doesn't include **
  • Intentionally allows slightly more permissive matches like ./*.*s, as that's what I'd expect to be convenient & reasonable alongside the count maximum

Adds an FAQs blog post to explain them.

💖

[typescript-eslint]

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[JoshuaKGoldberg]

Aside: filed #8926 to reduce the scale of this kind of huge FAQs list.

[JoshuaKGoldberg]

Aside: we'll definitely want more explanation here 😄 but quickly noted this in the meantime. Once this & a few more v8 milestone PRs are in, #7350 tracks a full blog post / explainer / revamp.

[me4502]

Is this meant to impact situations where EXPERIMENTAL_useProjectService is set to true? Not sure if it's a bug (will make an issue if it is), but I'm now seeing Parsing error: Too many files (>8) have matched the default project. for every single file in each workspaces' lint run as of 7.8.0.

From my understanding the project service should be loading the closest tsconfig.json in the file tree, and using the default if it doesn't match an included file, correct? It seems to be either ignoring the tsconfig.json file per workspace or ignoring the includes values in each one.

[JoshuaKGoldberg]

Hmm, every single file hitting this does sound like a bug. I'd appreciate an issue - yes please!

[me4502]

Will do, thanks. I haven't managed to reproduce this outside of one specific large & complex monorepo, so I'll see if I can narrow it down to reproduce.

[ehoogeveen-medweb]

I'm also seeing this match every file when linting a directory containing a project config, even after setting allowDefaultProjectForFiles: []. I'll try to get a minimal reproduction.

[ehoogeveen-medweb]

Here's a simple reproduction:

1. Clone https://github.com/ehoogeveen-medweb/glob-too-wide.git
2. Run npm ci
3. Run npx eslint --ext ts .

You should see something like this:

path/to/foo08.ts
  0:0  error  Parsing error: Too many files (>8) have matched the default project.

Having many files run with the default project is known to cause performance issues and slow down linting.

See https://typescript-eslint.io/troubleshooting/#allowdefaultprojectforfiles-glob-too-wide

Matching files:
- path/to/foo00.ts
- path/to/foo01.ts
- path/to/foo02.ts
- path/to/foo03.ts
- path/to/foo04.ts
- path/to/foo05.ts
- path/to/foo06.ts
- path/to/foo07.ts
- path/to/foo08.ts

If you absolutely need more files included, set parserOptions.EXPERIMENTAL_useProjectService.maximumDefaultProjectFileMatchCount_THIS_WILL_SLOW_DOWN_LINTING to a larger value

✖ 1 problem (1 error, 0 warnings)

[stepankuzmin]

Having the same issue with Too many files (>8) have matched the default project after upgrading to 7.8.0.

Setting maximumDefaultProjectFileMatchCount_THIS_WILL_SLOW_DOWN_LINTING to a large number helps.

[JoshuaKGoldberg]

Heyall, per our PR contributing guide please don't post on resolved PRs. The comments tend to get lost and this isn't an effective way to discuss issues. Please file a new issue with the appropriate template if you've got something to report that hasn't yet been reported.

#9032 tracks the general case of this error. Nobody's investigated to see what the actual issue is (if you have time, please do!). That would be the issue to subscribe to for updates. If you've got any new information to add such as investigation results or a new kind of reproduction, please add it there. Saying "I also have this issue!" doesn't give us any information and just gives an unnecessary notification to everyone in the thread.

maximumDefaultProjectFileMatchCount_THIS_WILL_SLOW_DOWN_LINTING is appropriately obnoxiously named. It's a "bandaid" solution to files being unmatched by the project service. A better solution is to figure out why they're unmatched and fix that bug - which is either in the ESLint config being used or in typescript-eslint.

Thanks for trying out the new project service though! Very exciting to see folks using it & giving feedback. Even if it's a bug on our end. 😄 ❤️