faq.md

What about semverver?

semverver uses a compiler driver to diff rlibs:

• This will thoroughly catch breaking changes for a given target and feature set.
• By being a compiler driver, it is coupled to a specific nightly toolchain (highly unstable APIs) and can be finicky to install.
• At the moment, this is limited to diffing rlibs and won't catch breaking changes in your Cargo.toml

What about cargo-breaking?

cargo-breaking's current release is built on the equivalent of cargo-expand and then parsing the resulting output with syn:

• Requires recreating Rust's pub rules (at this time it is [severely lacking](Requires recreating all )).
• Technically, this is using nightly features behind the scenes but they are fairly static, being compatible with a wide range of nightly versions.
• It only supports different against a previous git revision and wipes away your working tree in doing so.

There is a branch to switch to rustc. This seems like it'd make fairly similar to semverer.

So how is cargo-crate-api different?

cargo-crate-api started in a conversation with cargo-breaking authors on alternative approaches. The idea of building on top of rustdoc -wjson came up. cargo-crate-api started as a proof-of-concept for the idea. Further collaboration is still being determined.

Highlights:

• Leverages rustdoc for visibility logic
• Coupled to nightly for rustdoc json output but we are hoping this has a lower rate of churn than rustc APIs
• Can diff against git revisions (without destroying your working tree) and other paths
• Includes checking for breaking changes in Cargo.toml

Why not report back a suggested version?

cargo-breaking can output what version to bump to. For now we forego this out of concern for people exclusively relying on cargo-crate-api to determine whether there are breaking changes, rather than using it as a safety to catch unexpected breaking changes.