Protobuf version check does not play well with semver

[cheme]

This line does not work well with semver cargo expectation:

rust-libp2p/core/src/keys_proto.rs

Line 27 in 1aeb264

const _PROTOBUF_VERSION_CHECK: () = ::protobuf::VERSION_2_8_1;

result in https://gitlab.parity.io/parity/substrate/-/jobs/341902
It would either require to have a fix versioning in cargo.toml or check over every version that match semver requirement. Not sure what is better.

[bltavares]

I've started a test project and found this issue. I've partially solved it by pinning the version of protobuf crate on my Cargo.toml

[dependencies]
libp2p = "0.13.1"
protobuf = "=2.8.1"

[tomaka]

#1353 fixed it for the stable-futures branch.
Should we release a version 0.13.2 with protobuf pinned down (cc #1365), or is it fine to wait for 0.14?

[cheme]

It seems to break substrate ci so I would +1 in favor of 0.13.2 with protobuf pinned down.

[tomaka]

Theoretically Substrate should only break if someone updates the Cargo.lock to use a new protobuf version.

[cheme]

Yes, that is the 'try_build' check that breaks: https://gitlab.parity.io/parity/substrate/-/jobs/341902 (it seems to use its own lock internally, I am not sure of the purpose of this test but it may be to detect such issue).