Breaking Change: meta.feature-exists()
Themeta.feature-exists() function hasn’t had any new features added in a long time, and is now deprecated. Users should use other methods to determine if a new feature is available.
Historically, Sass used themeta.feature-exists() function (also available asthe globalfeature-exists() function) to allow authors to detect whethervarious new language features were available when compiling stylesheets.However, as time has gone on it’s turned out that the vast majority of new Sassfeatures are either possible to detect in a more straightforward way, or elsearen’t very useful to detect at all.
This function is now deprecated and will be removed in Dart Sass 2.0.0. SinceDart Sass is now the only officially supported Sass implementation, and allversions of Dart Sass support all the features supported bymeta.feature-exists(), all existing uses of it can safely be removed.
Many new features can be detected usingmeta.function-exists(),meta.mixin-exists(), or [meta.global-variable-exists()]. Others can bedetected using expression-level syntax, such as usingcalc(1) == 1 todetermine if the current version of Sass supports first-class calculations.
Transition PeriodTransition Period permalink
- Dart Sass
- since 1.78.0
- LibSass
- ✗
- Ruby Sass
- ✗
First, we’ll emit deprecation warnings for all usages offeature-exists.
In Dart Sass 2.0.0,meta.feature-exists() will no longer exist. Attempts tocall it will throw an error, and attempts to call the globalfeature-exists()function will be treated as a plainCSS function call.
Can I Silence the Warnings?Can I Silence the Warnings? permalink
Sass provides a powerful suite of options for managing which deprecationwarnings you see and when.
Terse and Verbose ModeTerse and Verbose Mode permalink
By default, Sass runs in terse mode, where it will only print each type ofdeprecation warning five times before it silences additional warnings. Thishelps ensure that users know when they need to be aware of an upcoming breakingchange without creating an overwhelming amount of console noise.
If you run Sass in verbose mode instead, it will printevery deprecationwarning it encounters. This can be useful for tracking the remaining work to bedone when fixing deprecations. You can enable verbose mode usingthe--verbose flag on the command line, ortheverbose option in the JavaScript API.
⚠️ Heads up!
When running from theJSAPI, Sass doesn’t share any information acrosscompilations, so by default it’ll print five warnings foreach stylesheetthat’s compiled. However, you can fix this by writing (or asking the author ofyour favorite framework’s Sass plugin to write) acustomLogger that onlyprints five errors per deprecation and can be shared across multiple compilations.
Silencing Deprecations in DependenciesSilencing Deprecations in Dependencies permalink
Sometimes, your dependencies have deprecation warnings that you can’t doanything about. You can silence deprecation warnings from dependencies whilestill printing them for your app usingthe--quiet-deps flag on the command line, orthequietDeps option in the JavaScript API.
For the purposes of this flag, a "dependency" is any stylesheet that’s not justa series of relative loads from the entrypoint stylesheet. This means anythingthat comes from a load path, and most stylesheets loaded through custom importers.
Silencing Specific DeprecationsSilencing Specific Deprecations permalink
If you know that one particular deprecation isn’t a problem for you, you cansilence warnings for that specific deprecation usingthe--silence-deprecation flag on the command line, orthesilenceDeprecations option in the JavaScript API.