Bug: Nested rule names don't work with flat config

[meeroslav]

Environment

Node version: v20
npm version: v10
Local ESLint version: 8.48.0
Global ESLint version: -
Operating System: MacOS Ventura (M1)

What parser are you using?

Default (Espree)

What did you do?

We have an ESlint plugin that dynamically adds users' rules as a nested rules using the convention @nx/workspace/{ruleName}. All the other static rules follow the typical convention @nx/{ruleName}.

You can see the code for it here:
https://github.com/nrwl/nx/blob/master/packages/eslint-plugin/src/index.ts#L40

What did you expect to happen?

This works fine with old configs/CLI.

What actually happened?

Running the same plugin with flat configs and environment flag returns following error:

TypeError: Key "rules": Key "@nx/workspace/demo-rule": Could not find plugin "@nx/workspace".

Link to Minimal Reproducible Example

https://github.com/beaussan/repro-nx-workspace-rule-with-flat-config

Participation

• I am willing to submit a pull request for this issue.

Additional comments

Changing resolution logic to name dynamic rules like @nx/workspace-{ruleName} works. Is this accidental omission on ESLint's side or are the nested rules names not supported anymore?

[meeroslav]

I realized this is by design https://github.com/eslint/eslint/blob/main/lib/config/flat-config-helpers.js#L25-L29 to support plugin names such as @scope/name. Not sure how/why this works in non-flat config.

Additionally, the logic above seems a bit odd as it converts string like @scope/foo/bar/baz into:

{ pluginName: '@scope/foo/bar', ruleName: 'baz' }

How can can plugin be named @scope/foo/bar? I would expect the logic to be something like:

        if (ruleId.startsWith("@")) {
            pluginName = ruleId.slice(0, ruleId.indexOf("/", ruleId.indexOf("/") + 1));
        } else {
            pluginName = ruleId.slice(0, ruleId.indexOf("/"));
        }

which would map above string to:

{ pluginName: '@scope/foo', ruleName: 'bar/baz' }

[nzakas]

Yes, you can't have a plugin namespace of @nx, as in your example, as this isn't a valid plugin name in eslintrc. We carried that behavior over for compatibility reasons. I'd expect you to still use @nx/eslint-plugin as the plugin namespace.

[meeroslav]

Yes, we use the @nx/eslint-plugin so each rule is scoped under @nx:

• @nx/enforce-module-boundaries
• @nx/dependency-checks

And I have renamed the old @nx/workspace/{rule} to @nx/workspace-{rule}. This works fine now in both classic and flat config.

Can you comment on my second message @nzakas? How come is @scope/foo/bar/baz parsed to:

{ pluginName: '@scope/foo/bar', ruleName: 'baz' }

The tests explicitly check this, so it must be intentional. That 3-segment name doesn't seem to be valid, though.

[nzakas]

This is consistent with how eslintrc normalized plugin names:

plugins:
- @scope/foo/bar

ESLint would expand it to @scope/eslint-plugin-foo/bar. See this test.

[meeroslav]

Feel free to change this from bug to question