Support ESLint 9 and Flat config

[brettz9]

Description

Please add support for ESLint 9, including Flat config support.

See:

1. https://eslint.org/docs/latest/use/configure/configuration-files-new
2. https://eslint.org/blog/2022/08/new-config-system-part-1/
3. https://eslint.org/blog/2022/08/new-config-system-part-2/
4. https://eslint.org/docs/latest/use/configure/migration-guide

Thanks!

[erichosick]

Want to try and work on this a bit. Trying to follow the pattern in eslint-plugin-n

import promise from 'eslint-plugin-promise';

/// TODO: Get the package name and version from package.json
const mod = {
  meta: {
    name: 'eslint-plugin-promise', /// pkg.name,
    version: '6.1.1', /// pkg.version,
  },
  rules: promise.rules, /// the rule definitions
}

const recommendedConfig = {
  flat: {
    languageOptions: {}, /// no language options for promise that I know of
    rules: promise.configs.recommended.rules, /// the rules we are applying
  }
}

/// really not sure how the eslint-plugin-promise wants to expose their
/// but here is a sort of guess.
mod.configs = {
  "flat/recommended": [
    {
      plugins: {
        promise: mod
      },
      files: ["**/*.js", "**/*.mjs", "**/*.cjs"],
      ...recommendedConfig.flat
    },
  ],
}

export default mod;

usage in flat file is something like:

// files: eslint.config.mjs

import promise from './eslint-plugin-promise-flat.mjs';
const flatConfig = promise.configs["flat/recommended"];

const eslintConfigObjects = [
  ...flatConfig,
];

export default eslintConfigObjects;

but when actually linting say no-promise-in-callback, getAncestors is undefined.

The line of code is here.

So, not quite sure why this is happening.

[brettz9]

Some of the APIs have been dropped in ESLint 9. context.getAncestors should be changed to SourceCode#getAncestors(node). See https://eslint.org/docs/latest/extend/custom-rules for the already deprecated items which are being dropped in ESLint 9.

[erichosick]

Heads up that the above link sends us to the older docs (at this time). Maybe this link instead? https://eslint.org/blog/2023/09/preparing-custom-rules-eslint-v9/#context.getancestors()

[brettz9]

Sure, I just meant the older docs for the fact that it had already been deprecated and a replacement was indicated there too. But yours is presumably even more current.

[erichosick]

Just one more note that the above example code does work for eslint v8. So, may be helpful for anyone wanting to use flat config in V8.

[TheElegantCoding]

+1 to this support

[doberkofler]

eslint v9 has just been released and support for v9 would be greatly appreciated

[voxpelli]

I'll try to find time to implement this if no-one beats me to it 👍

[crystalfp]

FYI. The rules that I had to disable to have eslint succeed are:

        "promise/no-return-wrap": "warn",
        "promise/no-promise-in-callback": "warn",
        "promise/no-nesting": "warn",
        "promise/no-callback-in-promise": "warn",