chacha: fix wasm32-unknown-unknown build

[ordian]

rand_chacha pulls rand_core/getrandom feature, which it doesn't seem to require.
This breaks wasm32-unknown-unknown builds.

[newpavlov]

Ideally, in addition to the std feature, I think it will be worth to add an enabled by default getrandom feature, which will enable rand_core/getrandom, so users will be able to use SeedableRng::from_entropy without enabling the std feature. It's also worth to check the other RNG crates and introduce similar changes.

[josephlr]

rand_core/std enables rand_core/getrandom, so I don't think we need to have rand_core/getrandom listed separately here?

[ordian]

Thanks, I find it a bit surprising though. Extracted getrandom in a separate feature now in 19de8ba.
Let me know if there is anything else that needs to be changed.

[newpavlov]

Looks good!

[dhardy]

I'm not actually sure how this helps — are you sure it isn't another dependency which depends on rand_core/std or rand_core/getrandom? (Assuming you are already disabling default features for rand_chacha in your build.)

Regarding adding the getrandom feature I don't see any harm, but it's also not really difficult to depend on rand_core/getrandom directly where required.

[dhardy]

rand_core doesn't have any default features, so this change does nothing IIUC

[ordian]

I'm not actually sure how this helps — are you sure it isn't another dependency which depends on rand_core/std or rand_core/getrandom? (Assuming you are already disabling default features for rand_chacha in your build.)

Regarding adding the getrandom feature I don't see any harm, but it's also not really difficult to depend on rand_core/getrandom directly where required.

Oh, you're right. I somehow overlooked the lack of default features. In my case the problem was caused by cargo's feature resolver v1 pulling optional crates it shouldn't have.