! Disclaimer !: This repository is no longer maintained and our advice is to use https://crates.io/crates/cargo-semver-checks instead.
cargo-breaking compares a crate's public API between two different branches,
shows what changed, and suggests the next version according to semver.
Suppose you're building a crate that, for any reason, deals with users. The
crate version is 2.4.3. You remove the User::from_str method, add a new public
field to User, implement Debug for it and add the User::from_path
function.
When invoked, the following text should be printed:
$ cargo breaking
- user::User::from_str
≠ user::User
+ user::User::from_path
+ user::User: Debug
Next version is: 3.0.0
against, an arg to specify the github ref (a tag, a branch name or a commit) against which we can compare our current crate version.
- use:
cargo breaking -a branch_name
- default: "main"
cargo-breaking aims to detect most breaking changes, but deliberately chooses
to ignore the most subtle ones. This includes, but is not limited to:
- when the size of a type changes (playground example),
- when a public trait is implemented for a type (see
assert_not_impl_any).
By default, cargo-breaking compares the public API of the crate against what
is exposed in the main branch. This can be changed with the --against
(abbreviated by -a) parameter. The value can be a branch name, a tag name, or
a commit SHA-1.
It currently detects the following:
- functions,
- struct fields and generic parameters,
- enum variants, fields and generic parameters,
- methods when the implemented type is simple enough.
As we compare parts of the crate AST, it reports a lot of false positives:
- renaming an argument is reported as a breaking change,
- renaming a generic type is reported as a breaking change,
- adding a generic type with a default value is a breaking change,
- depending on the situation, adding a trailing comma may be a breaking change.
A book is maintained to help understanding how the crate works, and what are its inner parts and their behaviour.
It can be found here : book