I've been trying to replicate an issue today & finally I have something by hacking around in my node_modules directory.

Basically, including a LESS file without an extension works, we know this... but... including without an extension from a node_modules directory fails.

I've created a simple repo demonstrating the following: https://github.com/robhuzzey/lessimporttest

@import './one/two/three/four/test'; works

as does: @import 'thisisinnodemodules/one/two/three/four/test.less';
(note that's including from node_modules with an extension)

However:

@import 'thisisinnodemodules/one/two/three/four/test';
(note that's including from node_modules without extension)

does not work and yields the following error:

$ npm run buildStyles

> lessissue@1.0.0 buildStyles /Users/robert.huzzey/Sites/test/lessissue
> lessc styles.less styles.css

FileError: 'thisisinnodemodules/one/two/three/four/test' wasn't found. Tried - /Users/robert.huzzey/Sites/test/lessissue/thisisinnodemodules/one/two/three/four/test.less,/Users/robert.huzzey/Sites/test/lessissue/thisisinnodemodules/one/two/three/four/test.less,/Users/robert.huzzey/Sites/test/lessissue/node_modules/thisisinnodemodules/one/two/three/four/test,thisisinnodemodules/one/two/three/four/test.less in /Users/robert.huzzey/Sites/test/lessissue/styles.less on line 5, column 1:
4 // This does NOT work
5 @import 'thisisinnodemodules/one/two/three/four/test';
6 

I've made a couple of branches to show this appears to be an issue with v3 but NOT v2... can anybody confirm if this is expected or undesired behaviour (I can't seem to find anything about this online).