Rule proposal: `no-submodule-import`

[fisker]

Description

A repo can contain many submodules, they should only share code via the entries, but not import internal files directly.

This rule should require a configuration step, it should look like

{
  'unicorn/this-rule-name': [
    'error',
    [
      {
        module: "a-module", // path to the module directory
        entries: [
          "index.js",
          "another-private-entry.js",
        ],
        message: "Please import functionality from `index.js` or `another-private-entry.js`"
      },
      // ... another submodule
    ]
  ]
}

Examples

// ❌
import {functionality} from "../a-module/internal-functionality.js"

// ✅
import {functionality} from "../a-module/index.js"

Proposed rule name

no-submodule-import

Additional Info

This is just the basic idea, open for discussion.

We should only support module with ./ or ../, we don't want to dive into the module resolution hell.

[fregante]

This setup is pretty project-specific IMHO. My attempt at this was a custom rule that blocked imports between specific folders as they were meant to be standalone: https://github.com/pixiebrix/pixiebrix-extension/blob/main/applications/browser-extension/eslint-local-rules/noCrossBoundaryImports.js

In your monorepo case, I think the rule could be implemented as a generic "don't import outside the root", with the "root" being defined by the location of package.json. Such a rule would be pretty reasonable even as a default, and I'm pretty sure it already exists in eslint-plugin-import if you want to take inspiration.