#[cfg_attrs { ... }]
Provides an alternative syntax to #[cfg_attr(...)]
that is easier to use with doc
comments.
Syntax
CfgAttrsAttribute :
cfg_attrs
Attribute :
ConfigureAttribute | OuterAttributeConfigureAttribute :
#
[
configure
(
ConfigureMeta)
]
ConfigureMeta :
ConfigurationPredicate,
AttributesAttributes :
_Attribute_* (,
_Attribute_* )*,
?
Usage
Placing #[cfg_attrs]
on an item enables a #[configure(<condition>, <attributes>)]
helper
attribute to be used on that item.
The syntax of that #[configure(...)]
attribute is much like #[cfg_attr(...)]
, except
the configured attributes use full attribute syntax. The advantage of this is that doc comments,
which expand to #[doc = "..."]
attributes, can be used in the #[configure(...)]
syntax.
Examples
/// This is an example struct.
This will expand to the following usage of #[cfg_attr(...)]
:
/// This is an example enum.
Which, if debug assertions are active, would be expanded to:
/// This is an example enum.
///
/// Hello! These are docs that only appear when
/// debug assertions are active.
Or, if the magic
feature is enabled:
/// This is an example enum.
#[cfg_attrs(...)]
may also be used with attributes other than doc comments, though there is
no real benefit to doing this:
With that example expanding to:
And expanding, if the magic
feature is enabled, to: