重大变化：meta.feature-exists()

从历史上看，Sass 使用 meta.feature-exists() 函数（也可用作全局 feature-exists() 函数）允许作者在编译样式表时检测各种新语言功能是否可用。但是，随着时间的推移，事实证明绝大多数新的 Sass 功能要么可以通过更直接的方式检测，要么根本检测不到。

¥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.

此功能现已弃用，将在 Dart Sass 2.0.0 中删除。由于 Dart Sass 现在是唯一官方支持的 Sass 实现，并且所有版本的 Dart Sass 都支持 meta.feature-exists() 支持的所有功能，因此可以安全地删除所有现有的使用。

¥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.

可以使用 meta.function-exists()、meta.mixin-exists() 或 [meta.global-variable-exists()] 检测许多新功能。可以使用表达式级语法检测其他功能，例如使用 calc(1) == 1 来确定当前版本的 Sass 是否支持一流计算。

¥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.

过渡期过渡期 permalink

¥Transition Period

兼容性:

Dart Sass

since 1.78.0

LibSass

✗

Ruby Sass

✗

首先，我们将针对所有 feature-exists 的使用发出弃用警告。

¥First, we’ll emit deprecation warnings for all usages of feature-exists.

在 Dart Sass 2.0.0 中，meta.feature-exists() 将不再存在。尝试调用它将引发错误，并且尝试调用全局 feature-exists() 函数将被视为普通的 CSS 函数调用。

¥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.

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.