How to specify multiple flags for an optional dep in Cargo.toml?

eee · March 21, 2025, 5:50pm

how can I enable multiple feature flags of a dependency if a certain feature flag of my crate is enabled?

I know how to do this for enabling a single feature flag, as demonstrated here:

tests/testsuite/publish.rs

307cbfda3


      
          foo_feature = [
              "normal-only/cat",
              "build-only/cat",
              "dev-only/cat",
              "renamed-dev-only01/cat",
              "normal-and-dev/cat",
              "target-normal-only/cat",
              "target-build-only/cat",
              "target-dev-only/cat",
              "target-normal-and-dev/cat",
              "optional-dep-feature/cat",
              "dep:optional-namespaced",
              "optional-renamed-dep-feature10/cat",
              "dep:optional-renamed-namespaced10",
          ]
          
          [dependencies]
          normal-only = { version = "1.0", features = ["cat"] }
          normal-and-dev = { version = "1.0", features = ["cat"] }
          optional-dep-feature = { version = "1.0", features = ["cat"], optional = true }
          optional-namespaced = { version = "1.0", features = ["cat"], optional = true }

and described here:

github.com/rust-lang/cargo

Allow specifying dependencies per feature

opened 07:59AM - 31 Aug 18 UTC

closed 12:41AM - 24 Oct 23 UTC

sdroege

A-features A-optional-dependencies

Most feature-dependency correspondences can currently be modeled by making the d…ependency optional but having the feature depend on this. This is not possible (from what I see) if "feature-a" and "feature-b" depend on the same crate but in different versions, as each crate can only be specified once. A syntax like the following would seem consistent for that case (and could also provide another way of specifying feature-dependant dependencies in general). ```toml [target.'cfg(feature = "feature-a")'.dependencies] foobar = "0.1" [target.'cfg(feature = "feature-b")'.dependencies] foobar = "0.2" ```

But is there some convenient syntax for writing a list of flags to enable? Or do I have to repetitively list them out like?;

my_feature = ["dep:mydep", "mydep/feature1", "mydep/feature2", "mydep/feature3"]

what I would like is:

my_feature = ["dep:mydep", "mydep/feature1,feature2,feature3"]

But I don't see that documented anywhere. Is it possible?

jwodder · March 21, 2025, 6:10pm

I believe "repetitively list[ing] them out" is your only option.

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How to specify multiple flags for an optional dep in Cargo.toml?

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