Getting test public keys is really expensive on debug builds

[eskimor]

This innocently looking line of code takes around 700ms on my machine on a debug build.

We should quickly check (if it is not obvious) why it takes that long and if there is nothing to do about it, provide caching via lazy_static as this would quite likely speed up test suits quite a bit.

[bkchr]

This is already a lazy_static 🤔

[burdges]

As a rule, deserializing a public key is never free because it involves operations like this inverse square root https://docs.rs/curve25519-dalek/3.1.0/src/curve25519_dalek/ristretto.rs.html#284 in sr25519, or much worse subgroup checks for pairing friendly curves. Is the .into() perhaps deserializing?

[eskimor]

Thanks @burdges ! @bkchr - haha, you are right! It is still slow as .... It likely is the into() call, that is slow.

[burdges]

After creation you could keep the keys in a deserialized state then somehow I guess, maybe breaks the key store abstraction somehow, but maybe some caching layer.

If this is what's happening then it'll get worse with the grandpa BLS key, which incurs an on-curve tests that takes much longer.