Import resolution

[sveetch]

Currently Boussole is very strict about import resolution: it refuses to compile sources which have import path that resolve to more than one source.

Note this is only an issue with "watch" mode which make introspection on Sass sources to find main sources to rebuild. With the "compile" mode, there is not introspection and this libsass which does everything, no boussole code is involved in import resolution.

Current behavior

If a source contains @import "foo" and there are foo.css and foo.scss files, it raises an error about unclear resolution since foo can be understood as foo.css or foo.scss. This can happen also with identical source file (relative) path with included libraries.

Expected behavior

This is not the way other compiler works especially node-sass. Even Sass documentation define another behavior: https://sass-lang.com/documentation/at-rules/import#load-paths

Also, we should fit to the node-sass behaviors so Boussole could be a valid replacement. And so we may have to implement the "~" behavior which seek for path from "node_modules" which path will have to be configured in settings.

Filename in current directory win against similar names from include libraries. This should be the default behavior to adopt (and strict could stay as an option).

Still there is some details to study to go further:

• How it should work when the only conflict is the extension (scss, css, sass) ? Keep raising an error ? Or should be resolve by priorities (which extensions are highest and lowest priority) ?
• Libraries priority comes from includes paths order as defined from settings ?

This must not replace the current import behavior and must be introduced as a new optional resolution engine (depending a setting?) and current behavior will still be the default one for some time as a deprecation process.

[sveetch]

For sanity, i checked compilation with Foundation, Bootstrap and Bulma from their node modules and everything is fine for compile and watch mode.

But as stated from issue detail, an exception is raised for conflicts, if the Sass project import Foundation and also contains a components/_badge.scss file, it make a conflict with the one from Foundation.

[sveetch]

Plan:

• Error for conflict should stay as a feature which can be disabled from a setting, it seems safe to turn it off on the next version;
• Resolution for the same pattern should have order base on proximity (a source from project win again a source from imported module) and then format extension (scss > sass > css);
• Libraries priority comes from order in library paths setting, so user can force a library to win, no matter alphabetical order or anything else;
• There is no need of a new engine, since conflict resolution error will just be disabled. We will have to add some new code for resolution discovering in inntrospection when error is disabled;
• "~" feature will be added from a new settings like base_modules for a path to search from import pattern, not sure for final implementation with the introspection. If need it will be move to a distinct issue to avoid blocking this one;