Bug: Type incompatibility with `fixupPluginRules()` from `@eslint/compat` about typescript-eslint

[bradzacher]

Wow they committed the cardinal sin of using Object.

https://github.com/eslint/rewrite/blob/d5a04961b99e4e3e529d631089a51b68581bb741/packages/compat/src/types.ts#L13-L15

Honestly I think that this is a bug in their types, not ours. You'll find that their types also don't work with @types/eslint.

They've ultimately defined these super loose janky types that nobody can align with.

We already define super loose types for this assignment to be permissive and accept many things - but they're even looser than we are which is insane to consider.

typescript-eslint/packages/utils/src/ts-eslint/Rule.ts

Lines 667 to 688 in 510153b

	export type LooseRuleDefinition =
	// TODO - ESLint v9 will remove support for RuleCreateFunction
	| LooseRuleCreateFunction
	| {
	meta?: object | undefined;
	create: LooseRuleCreateFunction;
	};
	/*
	eslint-disable-next-line @typescript-eslint/no-explicit-any --
	intentionally using `any` to allow bi-directional assignment (unknown and
	never only allow unidirectional)
	*/
	export type LooseRuleCreateFunction = (context: any) => Record<
	string,
	/*
	eslint-disable-next-line @typescript-eslint/ban-types --
	intentionally use Function here to give us the basic "is a function" validation
	without enforcing specific argument types so that different AST types can still
	be passed to configs
	*/
	Function | undefined
	>;

So yeah I'd file an issue upstream and get them to define something that'll work with the existing ecosystem.

((separately they should consider using our recommended rule set on their TS files to catch such issues))

[karlhorky]

Good point, thanks! I also was able to confirm that the @eslint/compat types are incompatible with the Linter.FlatConfig[] type from @types/eslint.

I reported it over here:

• eslint/rewrite#25

[bradzacher]

I'll close this out then as there's nothing for us to action from our side.