s2n-quic 1.45 is semver breaking

[SergioBenitez]

The s2n_quic::application::Error type implements From<VarInt> from s2n-quic-core. In 1.44, VarInt was from version 0.44 of s2n_quic_core. In 1.45, VarInt is from the semver incompatible s2n_quic_core 0.44 resulting in a breaking change for any users of the public From<VarInt> impl.

The only correct fix is to provide an implementation of From<VarInt> for the 0.44 version of VarInt as well. Turning back time, VarInt should either be hidden entirely from public APIs or reexported from the s2n-quic crate.

[camshaft]

We don't currently have any guarantees around breaking changes for our 0.x crate, in this case s2n-quic-core. Only types accessible by the s2n-quic crate are considered for semver.

Is there a reason you're needing to depend on s2n-quic-core?

[SergioBenitez]

This a breaking change in s2n_quic, not s2n_quic_core, though it is precipitated by a change to the latter. The use of core occurs through the h3 integration.

Only types accessible by the s2n-quic crate are considered for semver.

I'm not quite sure what this means. The s2n-quic crate exposes a public API that uses types from another crate. Irrespective of whether you export those types or not, they become part of your public API and are subject to the same semver rules.

[WesleyRosenblum]

Our s2n-quic-h3 crate should not have depended on s2n-quic-core, given the recommendation from the readme:

This is an internal crate used by s2n-quic. The API is not currently stable and should not be used directly.

I've gone ahead and removed that dependency in #2325, and would suggest you make a similar change to your code.