import/extensions ignores extension overrides if ignorePackages is set in object options

[le0nik]

node: v10.14.1
eslint: v5.10.0
eslint-plugin-import: v2.14.0

.eslintrc.js

module.exports = {
  plugins: ['import'],
  rules: {
    'import/extensions': ['error', 'always', {
      ignorePackages: true,
      js: 'never',
    }]
  }
}

./src/index.js

import app from './app';

Running eslint results in an error:

/Volumes/Projects/project/src/index.js
1:22  error  Missing file extension "js" for "./app"  import/extensions

The problem seems to be here https://github.com/benmosher/eslint-plugin-import/blob/1cd82eb27df85768fbd076e4ff6b7f36d6f652ce/src/rules/extensions.js#L36-L45

Plugin expects extensions overrides to be specified inside pattern property inside the options object if ignorePackages property is also specified. It's not documented here though.

So this configuration works correctly:

{
  rules: {
    'import/extensions': ['error', 'always', {
      ignorePackages: true,
      pattern: { // wrap extensions in the `pattern` object
        js: 'never',
      }
    }]
  }
}

Either documentation is lacking or pattern property should not be expected in options.

[ljharb]

Ths doesn’t seem resolved yet?

[ivo-stefchev]

Oh, how I love explicit configs.
So the reason why this doesn't work:

module.exports = {
  plugins: ['import'],
  rules: {
    'import/extensions': ['error', 'always', {
      ignorePackages: true,
      js: 'never',
    }]
  }
}

is because in order to apply the js part - you need to have ingnorePackages to be undefined. So basically if ignorePackages is present in the object - it disables all extension specific options. For me at least this makes very little sense

[ivo-stefchev]

Also this defaultConfig is enum of three possible values.

"import/extensions": [<severity>, "never" | "always" | "ignorePackages"]

ignorePackages doesn't do anything when you set it, hence I propose to be removed from the enumValues and left only as boolean property part of the object.

[ljharb]

Seems like a good PR.