I realized that, if we're extremely vague about what the parser, plugin, and configs are, we can easily satisfy both the expected types fromdefineConfig() andtseslint.config(), without running into the many incompatibilities I experienced during previous attempts. While this sacrifices precision, the exact shapes of those objects aren't actually important at all to users; it's only important that they be usable within their configs. So, I think this is a worthwhile tradeoff.

It's possible that some plugin authors, or downstream consumers that use our tools in some way other than in their lint configuration might experience some type errors as a result of this. Fixing these errors should be quite simple, since one can use type assertions to get the previous (also quite vague) types:

tseslint.parserasFlatConfig.Parser;tseslint.pluginasFlatConfig.Plugin;tseslint.configs['foo']asFlatConfig.Config|FlatConfig.ConfigArray

provide compatible types

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typescript-eslintbot commentedAug 13, 2025

Thanks for the PR,@kirkwaiblinger!

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nx stuff?

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thernstig commentedAug 14, 2025

Shouldn't this also be updated?

typescript-eslint/docs/getting-started/Quickstart.mdx

Lines 54 to 63 inb2ee794

	<details>
	<summary>Aside on ESLint's`defineConfig()`</summary>

	ESLint also provides a`defineConfig()` helper similar to`tseslint.config()`.
	However, there is a types incompatibility issue that causes type errors to incorrectly be reported when mixing typescript-eslint's configs and`defineConfig()`.
	For now we recommend using`tseslint.config()` for use with typescript-eslint's configs.

	See[typescript-eslint#10899](https://github.com/typescript-eslint/typescript-eslint/issues/10899) for more details.

	</details>

Along with the example on that same page to start usingdefineConfig instead?

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kirkwaiblinger commentedAug 14, 2025

@thernstig

Shouldn't this also be updated?
typescript-eslint/docs/getting-started/Quickstart.mdx
Lines 54 to 63 inb2ee794
<details>
<summary>Aside on ESLint's`defineConfig()`</summary>
ESLint also provides a`defineConfig()` helper similar to`tseslint.config()`.
However, there is a types incompatibility issue that causes type errors to incorrectly be reported when mixing typescript-eslint's configs and`defineConfig()`.
For now we recommend using`tseslint.config()` for use with typescript-eslint's configs.
See[typescript-eslint#10899](https://github.com/typescript-eslint/typescript-eslint/issues/10899) for more details.
</details>

Possibly could... Though in the name of caution it might be worth releasing the types change and waiting a week to make sure it's doesn't end up messing up people's configs too before we take down the notice. Could go either way.

Along with the example on that same page to start usingdefineConfig instead?

This will for sure not happen as part of this PR, but endorsingdefineConfig()is tracked separately as#10935

bradzacher approved these changes

Aug 16, 2025

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packages/typescript-eslint/tests/type-compatibility.test-d.ts

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istest-d.ts run by vitest? TIL

bradzacher merged commit3426f0d intotypescript-eslint:main

Aug 16, 2025

114 of 121 checks passed

kirkwaiblinger deleted the fix-define-config-incompatibility branch

August 16, 2025 04:12

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Martinspire commentedAug 19, 2025

If another way of configuring the project is supported, shouldn't the overall readme have a way to do this? I mean, if you want people to start using it, it would be nice to know how it works...

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thernstig commentedAug 19, 2025

If another way of configuring the project is supported, shouldn't the overall readme have a way to do this? I mean, if you want people to start using it, it would be nice to know how it works...

See#10935