Mutually Exclusive Features Unsupported By Cargo

[krakow10]

This crate uses mutually exclusive features compile-time-rng, runtime-rng, and no-rng. The default behaviour of cargo is to enable the superset of all enabled features of all dependencies in the tree. There should be some kind of compile error if a conflicting set of features are enabled to prevent other people from having the same difficult-to-diagnose issue as me.

[tkaitchuck]

What was the issue you saw? It should default to the strongest enabled, So if you had all three on that would be runtime-rng.

[krakow10]

Indeed, but my requirements were the weakest, I was using it for a hash at compile time, no-rng. The other crates in the tree caused multiple feature flags to be enabled at once, and then all users of ahash got runtime-rng. I ended up dropping all the feature flags and manually specifying a specific RandomState.

[tkaitchuck]

Yes, if you want a fixed seed, it's best to pass it in directly.

[krakow10]

My point is that the surprising behaviour still lurks there for others to run into. I didn't know that cargo uses the superset of all requested features in the tree until I ran into this issue. Perhaps they should be RandomState constructors rather than feature flags.