provide type support for .eslintrc.js

[tadhgmister]

I really appreciate my IDE's suggestions and intellisense, and it always bugged me that the eslintrc had no support.

Today I found that the basic structure of the eslintrc format is present in Linter.ts so today I added this to my .eslintrc.js for my personal repo:

// @ts-check
/** @type {import("@typescript-eslint/experimental-utils/dist/ts-eslint/Linter").Linter.Config} */
const config = {
     ...
};
module.exports = config;

This internal type doesn't contain any rule information but I think an official version of this would be desirable:

• it could be generated with a similar script to generate-configs.ts
• both type check, and give auto-complete for specifying options
• can make configuration for base rules that don't work so users get errors like this:

(code that produces above message)

As well with namespace merging it should be possible to provide an easy way for other packages to define a .d.ts file to define their own rule options, something like this would be useful:

declare namespace ESLINT {
    type Severity = 0 | 1 | 2 | "off" | "warn" | "error";
    type RuleOption<Settings extends unknown[] = []> = Severity | [Severity, ...Settings];
    interface Rules extends Record<string, RuleOption<unknown[]>> {
        "no-shadow": "off";
        "@typescript-eslint/no-shadow": RuleOption<[]>;
    }
}
// in another library:
declare namespace ESLINT {
    interface Rules {
        "import/first": RuleOption; // specific options specified
    }
}

I think there might be a way to allow this without polluting the global namespace but it'd require some investigation.

In any case I do think this is worth some consideration and I am more than happy to implement It.

[tadhgmister]

never mind, duplicate of #1296,