ESLint Plugin: Ship type declarations for the public API - #82739

What?

Closes #82494

Adds TypeScript type declarations to @wordpress/eslint-plugin, so it can be used from a type-checked eslint.config.ts without a declare module shim.

Why?

The package ships no declarations, so importing it in a typed flat config fails:

TS7016: Could not find a declaration file for module '@wordpress/eslint-plugin'.

With typescript-eslint strict rules on, the resulting any also triggers no-unsafe-member-access and no-unsafe-assignment in the config itself. Consumers currently work around it with an ambient module shim.

How?

Adds three declaration files under packages/eslint-plugin/types/:

• shared.d.ts: the ConfigName and RuleName unions, PluginMeta and Rules, shared by both entry points.
• index.d.ts: the main export, with configs typed as Record<ConfigName, Linter.Config[]>.
• eslintrc.d.ts: the same for the deprecated /eslintrc export, using Linter.LegacyConfig.

Config and rule names are string literal unions, so only names the plugin actually exports are accepted. ESLint.Plugin was not reused directly because it types configs as Record<string, unknown>, which loses that precision. The plugin object is still assignable to ESLint.Plugin.

Also:

• package.json: adds the types field, a types condition on both export subpaths, and types to files.
• Drops the @types/eslint dev dependency. ESLint ships its own types since 9.10, and having both risks checking against the older DefinitelyTyped shapes. Only this package declared it.
• tsconfig.json: adds the declarations to files and widens rootDir to . so they are type checked.
• README: documents typed config usage.

Testing Instructions

1. npm install
2. npm run typecheck passes.
3. npm run lint:js and npm run lint:pkg-json pass.

To check the consumer side:

1. npm pack --workspace @wordpress/eslint-plugin

2. Install the tarball in a scratch project with eslint@^10, typescript, jiti and typescript-eslint.

3. Add an eslint.config.ts:

   import { defineConfig } from 'eslint/config';
   import wordpress from '@wordpress/eslint-plugin';
   
   export default defineConfig( {
   	extends: [ wordpress.configs.recommended ],
   } );

4. tsc --noEmit reports TS7016 before this change and passes after.

5. wordpress.configs[ 'not-a-config' ] and wordpress.rules[ 'not-a-rule' ] should be type errors.

6. eslint . still works the same. No rule or config code changed.

Testing Instructions for Keyboard

N/A, no UI changes.

Screenshots or screencast

N/A, types only.

Use of AI Tools

Claude Code was used to draft the declaration files, the config wiring and this description. I reviewed everything manually and tested on latest version of eslint.