Address Impact of Frequent Deprecations and MSRV Increases

[sujalsalekar]

Description

Recent versions of rust-libp2p have introduced significant breaking changes and deprecated core features, alongside frequent increases in the Minimum Supported Rust Version (MSRV). While continuous development and improvement are expected, the pace and nature of these changes, as seen in the CHANGELOGs (e.g., libp2p/CHANGELOG.md), pose challenges for users trying to maintain compatibility and upgrade their dependencies. Specific examples include the removal of Transport::with_bandwidth_logging, SwarmBuilder::with_bandwidth_logging, and TransportExt in 0.56.0, the removal of the mplex module, and MSRV bumps from 1.65 to 1.73 to 1.83.0 in relatively short periods.

Motivation

The current approach can lead to:

• Difficulty for users in upgrading dependencies due to unexpected breaking changes and removed features.
• Increased maintenance burden for downstream projects that need to constantly adapt to API changes and MSRV requirements.
• Potential for users to remain on older, unsupported versions to avoid migration complexities.
• Fragmentation within the ecosystem if users cannot keep up with the required Rust versions.

Addressing this issue is crucial for fostering a stable and accessible library that encourages broad adoption and reduces friction for contributors and users alike.

Current Implementation

The changes and deprecations are documented in the CHANGELOG.md files across the various crates (e.g., rust-libp2p/libp2p/CHANGELOG.md). The deprecated features have been removed or replaced, and the MSRV is enforced based on the Cargo.toml settings and CI. The current implementation requires users to make potentially significant code modifications and upgrade their Rust toolchains when updating to newer rust-libp2p versions.

Are you planning to do it yourself in a pull request?

Yes

[jxs]

Hi, and thanks for the feedback.
We make an effort to soft deprecate items, and give users of rust-libp2p time to upgrade, from the items you mention:

• with_bandwidth_logging was soft deprecated on version 0.53, which was released in December 2023
• the decision to deprecate mplex was taken by the libp2p community 2 years ago and also, the only difference with rust-libp2p is that it has to be explicitly depended on, but we still release it to match the recent libp2p dependencies, the last release was 5 months ago.
• MSRV, we have definitely jumped some versions recently due to the assumption that with Rust not introducing breaking changes updating the Rust version should be seamless.

Can you elaborate on what is specifically affecting your case, namely the MSRV?