feat!: Switch to flat config

[nzakas]

• Switch recommended config to flat config format
• Rename old recommended config to recommended-legacy
• Updated documentation
• Upgraded ESLint and associated plugins
• Updated tests

fixes #231

[nzakas]

Ping @eslint/eslint-team

[mdjermanovic]

Which versions of ESLint will be officially supported? Per this sentence and the CI update, it looks like only >=8. However, there are still instructions for v6 and v7 below, and package.json still has "peerDependencies": { "eslint": "^6.0.0 || ^7.0.0 || ^8.0.0" } .

[nzakas]

I'm going to update the supported ESLint versions in another PR.

[aladdin-add]

this also dropped some node.js/eslint versions support. To reflect this in the generated changelog：

1. update the PR title.
2. put these changes to a separate PR.

[nzakas]

These changes are necessary to make CI pass. I'll officially change the Node.js supported versions in a separate PR.

[mdjermanovic]

If we want to drop support for Node < 16, we should also update the engines field in package.json.

[nzakas]

As previously mentioned, I'm going to update Node.js support in a separate PR so it comes out in the changelog.

[mdjermanovic]

Now that the eslint config for this project enables reporting unused disable directives, this directive is reported when linting is run after npm test, which is confusing. It might be best to allow requiring eslint-plugin-markdown from this file and remove this directive (and the same one on line 1065).

// in eslint.config.js
{
    files: ["tests/lib/plugin.js"],
    rules: {
        "n/no-missing-require": ["error", {
            allowModules: ["eslint-plugin-markdown"]
        }]
    }
}

[mdjermanovic]

Actually, we can now just remove the whole try-catch (lines 73-95 and 1059-1081) as there's no need to install eslint-plugin-markdown in node_modules.

As of ESLint v8.1.0 (eslint/eslint@a1f7ad7), plugin implementations passed to the constructor are used when resolving extends:["plugin:plugin-name/config-name"] as well. In this case, eslint-plugin-markdown implementation we're already passing to the ESLint constructor will be used to get the "plugin:markdown/recommended-legacy" config from.

[nzakas]

Ah good catch!

[mdjermanovic]

As of v7.32.0, eslint-plugin-react has an additional export for the recommended config in flat config format, so we could use that for this example:

require('eslint-plugin-react/configs/recommended') // this is a flat config object

[mdjermanovic]

Suggested change

plugins: { markdown: plugin },

This doesn't seem necessary as the config files load the plugin.

[mdjermanovic]

LGTM, thanks!