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Unify weak and namespaced features. by ehuss · Pull Request #9574 · rust-lang/ca...

 3 years ago
source link: https://github.com/rust-lang/cargo/pull/9574
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ehuss commented 20 days ago

This unifies weak and namespaced features in order to simplify the syntax and semantics. Previously there were four different ways to specify the feature of a dependency:

  • package-name/feature-name — Enables feature package-name on self and enables feature-name on the dependency. (Today's behavior.)
  • package-name?/feature-name — Only enables feature-name on the given package if it that package is enabled and will also activates a feature named package-name (which must be defined implicitly or explicitly).
  • dep:package-name/feature-name — Enables dependency package-name, and enables feature-name on that dependency. This does NOT enable a feature named "package-name".
  • dep:package-name?/feature-name — Only enables feature-name on the given package if it that package is enabled. This does NOT enable a feature named "package-name".

This changes it so there are only two:

  • package-name/feature-name — Today's behavior.
  • package-name?/feature-name — Only enables feature-name on the given package if it that package is enabled. This does NOT enable a feature named "package-name" (the same behavior as dep:package-name?/feature-name above).

This is a fairly subtle change, and in most cases probably won't be noticed. However, it simplifies things which helps with writing documentation and explaining how it works.


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