Omitting the '.less' file extension causes problems in environments where you are importing different types of files. Currently the code
@import 'foo';
in a folder with 'foo.css' and 'foo.less' will import the latter (foo.less). In Webpack or any JS bundler, it will throw an error as it will assume it is a package with an index.css or index.js file meaning the code cannot be used.
I would thus propose we change this convention. In the web team, we've been using code outside ResourceLoader, for example to create this storybook instance: https://doc.wikimedia.org/MobileFrontend/master/js/ui/?path=/story/*
To workaround this issue in the meantime we have to create extension-less files like this one: https://github.com/wikimedia/mediawiki-extensions-MobileFrontend/blob/master/.storybook/resolve-less-imports/mediawiki.ui/variables I would rather not do that.