Add setting for specifying internal module directories

[Whoaa512]

Closes #807

[coveralls]

Coverage increased (+0.01%) to 96.004% when pulling f2f689c on Whoaa512:custom-internal-modules into cd77133 on benmosher:master.

[jjshammas]

Any movement on this? Would love to have this feature so we can properly order the import/order rule.

[ljharb]

How should this setting interact with https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-internal-modules.md and other rules?

Please add tests for any impacted rules, ideally both a valid and an invalid one.

[Whoaa512]

I don't have time to work on this in the next few months.

@jjshammas Feel free to pick it up and make the necessary changes.

[ljharb]

@jjshammas please don’t make a duplicate PR; either post a link here to your branch and i can pull in the commits, or, @Whoaa512 can add you as a collaborator on their fork, and you can make changes directly there.

[stramel]

@ljharb Did you have any thought or preference on how you think it should handle no-internal-modules?

[ljharb]

@stramel I'm not sure - it's probably a lot of complexity, and I think that the research needs to be done before making a change here.

[robatwilliams]

Matching using folder name startsWith wouldn't identify an internal module imported from a sibling: ../anInternalModule. Does it need to do something similar to isExternalPath?

New setting needs to be documented in the readme, and linked to from the "related" section of the order rule's docs page, as has been done with the import/external-module-folders setting.

[rodrigobdz]

@stramel Did you gain any insights into how to handle no-internal-modules?

[JuHwon]

fyi: this implementation does not work, when configuring internal-module-folders with something like src/. src/ will still be recognized as external module.

[benmosher]

closing on account of staleness + I would rather not add global settings just for this, would prefer the suggestion in this comment