sass/accepted/remove-feature-exists.md

feature-exists removal: Draft 1.0

(Issue)

This proposal removes feature-exists in the built-in sass:meta module.

Table of Contents

• Background
• Summary
• Deprecation Process
  • feature-exists

Background

This section is non-normative.

feature-exists is ill-defined as nothing specifies what each feature actually requires to be considered as supported. The shared sass-spec testsuite does not cover this either. Thus, no new feature identifier has been added in it for years.

New Sass features essentially fall into one of three categories:

1. New built-in functions or mixins, which are easy to detect using other sass:meta functions.
2. Language-level features which are relatively easy to detect on their own (for example, first-class calc can be detected with calc(1 + 1) == 2).
3. New syntax which can't even be parsed in implementations that don't support it, for which feature detection isn't particularly useful anyway.

Summary

This section is non-normative.

The feature-exists function of sass:meta and its global alias will be removed without any direct replacement.

Deprecation Process

The feature-exists function will be supported until the next major version with a deprecation warning.

feature-exists

During the deprecation period, when invoking the feature-exists function, emit a deprecation warning named feature-exists.