[import/order] Regression in 2.20.1

[South-Paw]

Installed 2.20.1, started getting ordering errors like the following;

Our rule for import/order is

'import/order': [
  'error',
  {
    groups: ['builtin', 'external', 'parent', 'sibling', 'index'],
    'newlines-between': 'never',
  },
],

Rolling back eslint-plugin-import to 2.20.0 resolves the issue.

[yoyo837]

Seems to be seen only on Windows. 🤔

[ljharb]

That makes testing for it difficult; appveyor tests are currently failing for unrelated reasons.

[targos]

What I found by debugging:

• The import type of an external module is not determined as such
• The reason is that the path passed to isSubpath contains Windows separators (backslashes) and the function expects slashes.

https://github.com/benmosher/eslint-plugin-import/blob/45f08609e0dd79f2a061c3411a43169c20e80d3a/src/core/importType.js#L31-L41

[ljharb]

path.normalize and path.sep might help us here?

[kryops]

This also seems to affect import/no-extraneous-dependencies: As the import type is reported as internal instead of external due to the path containing backslashes, the rule never reports any errors on Windows.

[kryops]

I tried to create a minimal reproduction for the import/order and import/no-extraneous-dependencies rules: https://github.com/kryops/eslint-plugin-import-issue1643

[ljharb]

A PR with a failing test case would be most welcome; I can add a fix to that (altho a PR that has both is even better!)

[targos]

I think the existing tests should already fail on Windows. I was unable to run the tests on that platform when I tried today, though.