The Module System is Launched

The Sass team has known for years that the @import rule, one of the earliest additions to Sass, wasn’t as good as we wanted it. It caused a litany of problems for our users:

• It was next to impossible to figure out where a given variable, mixin, or function (collectively called “members”) was originally defined, since anything defined in one stylesheet was available to all stylesheets that were imported after it.
• Even if you chose to explicitly import every stylesheet that defined members you used, you’d end up with duplicate CSS and strange side-effects, because stylesheets were reloaded from scratch every time they were imported.
• It wasn’t safe to use terse and simple names because there was always a possibility that some other stylesheet elsewhere in your application would use the same name and mess up your logic. To be safe users had to manually add long, awkward namespaces to everything they defined.
• Library authors had no way to ensure that their private helpers wouldn’t be accessed…