Can you test if a feature of a dependency is set using the `cfg!` macro?

help
1

Can you test if a feature of a dependency is set using the cfg! macro? Something like:

if cfg!(feature = "some-dependency/some-feature") {
    println!("SET");
} else {
    println!("NOT SET");
}

Here is the question on stack overflow.

2

Yes.

3

Oh sorry, I didn't read the SO post which had more details. No it's not possible for dependencies.

4

Thanks, is there a fundamental reason that makes this functionality not possible? It seems odd that we can set them from the Cargo.toml files and the command line, but not read them with cfg.

5

I'm not at my pc so I can't test it, but if you run cargo build -vv it should show you the command line that cargo uses to call rustc. Since there's no --cfg argument for the dependency features, the compiler has no way of knowing. Sure, someone could add this feature to cargo, but this is how it is now.

6

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