Breaking Change: meta.feature-exists()
The meta.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 the meta.feature-exists() function (also available as
the global feature-exists() function) to allow authors to detect whether
various new language features were available when compiling stylesheets.
However, as time has gone on it’s turned out that the vast majority of new Sass
features are either possible to detect in a more straightforward way, or else
aren’t very useful to detect at all.
This function is now deprecated and will be removed in Dart Sass 2.0.0. Since
Dart Sass is now the only officially supported Sass implementation, and all
versions of Dart Sass support all the features supported by
meta.feature-exists(), all existing uses of it can safely be removed.
Many new features can be detected using meta.function-exists(),
meta.mixin-exists(), or [meta.global-variable-exists()]. Others can be
detected using expression-level syntax, such as using calc(1) == 1 to
determine 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 of feature-exists.
In Dart Sass 2.0.0, meta.feature-exists() will no longer exist. Attempts to
call it will throw an error, and attempts to call the global feature-exists()
function will be treated as a plain CSS function call.
Can I Silence the Warnings?Can I Silence the Warnings? permalink
Sass provides a powerful suite of options for managing which deprecation warnings 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 of deprecation warning five times before it silences additional warnings. This helps ensure that users know when they need to be aware of an upcoming breaking change without creating an overwhelming amount of console noise.
If you run Sass in verbose mode instead, it will print every deprecation
warning it encounters. This can be useful for tracking the remaining work to be
done when fixing deprecations. You can enable verbose mode using the
--verbose flag on the command line, or the verbose option in the
JavaScript API.
⚠️ Heads up!
When running from the JS API, Sass doesn’t share any information across
compilations, so by default it’ll print five warnings for each stylesheet
that’s compiled. However, you can fix this by writing (or asking the author of
your favorite framework’s Sass plugin to write) a custom Logger that only
prints 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 do
anything about. You can silence deprecation warnings from dependencies while
still printing them for your app using the --quiet-deps flag on the command
line, or the quietDeps option in the JavaScript API.
For the purposes of this flag, a "dependency" is any stylesheet that’s not just a series of relative loads from the entrypoint stylesheet. This means anything that 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 can
silence warnings for that specific deprecation using the
--silence-deprecation flag on the command line, or the silenceDeprecations
option in the JavaScript API.
⚠️ Heads up!
This option is only available in the modern JS API.