docs: blog post on parserOptions.projectService

[JoshuaKGoldberg]

PR Checklist

• Addresses an existing open issue: fixes Docs: Add blog post for EXPERIMENTAL_useProjectService #7350
• That issue was marked as accepting prs
• Steps in Contributing were taken

Overview

Adds a blog post that describes using parserOptions.projectService (what we currently call parserOptions.EXPERIMENTAL_useProjectService). It sets up a plan to call it projectService in v7, then replace project in v8.

Note that this is blocked on:

• feat(typescript-estree): add allowDefaultProjectForFiles project service allowlist option #7752: for locking down how an "additional files / to be given default program type info" should look
• feat: add support for flat configs #7935: for example flat configs in the post
• Creating a set of example configs on a new, not-yet-created https://github.com/typescript-eslint/examples
• Enhancement: Finalize naming for EXPERIMENTAL_useProjectService #9004
• Creating and running performance comparisons on a new, not-yet-created https://github.com/typescript-eslint/project-apis-performance-comparison

This is where my mindset is for the option.

💖

[typescript-eslint]

Thanks for the PR, @JoshuaKGoldberg!

typescript-eslint is a 100% community driven project, and we are incredibly grateful that you are contributing to that community.

The core maintainers work on this in their personal time, so please understand that it may not be possible for them to review your work immediately.

Thanks again!

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[bradzacher]

🤞 hopefully

[JoshuaKGoldberg]

Heh if we don't support flat config by the time this rolls out I will be in a lot of emotional pain...

[JoshuaKGoldberg]

Note: before un-drafting, I"ll want to revisit this and align it to how our flat config support ended up looking.

[bradzacher]

I personally don't like this advice because it's a lot wider than we might otherwise intend and will match all files in the root.
I think it's better to not suggest ./* and instead suggest being explicit to keep things narrow and cleaner.

[JoshuaKGoldberg]

Blurgh, I'm torn. It's rather inconvenient having to specify files by name. It's pretty common to have >=3 files there. https://github.com/JoshuaKGoldberg/create-typescript-app has ESLint, tsup, and Vitest right now.

Having a ['./*'] be the starting recommending means users can copy+paste without having to pause to tinker with individual file names. IMO the much smoother onboarding there is a pretty big value prop.

Given that #7752 has it throw an error if a file is redundantly included, what are the practical downsides of having a permissive glob?

[bradzacher]

note for before landing - this doesn't exist yet.

[JoshuaKGoldberg]

babel/babel#16192 ❤️ - would be nice to have a "success stories" section...

[Josh-Cena]

Great to see exciting features

[JoshuaKGoldberg]

Maybe also good to have - #7906 ...

[Jack-Works]

__dirname is not available inside an NodeJS ES Module.

Use import.meta.dirname (since v21.2.0) or join(fileURLToPath(import.meta.url), '..')

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