It is quite simple conceptually to decide. Simply examine all the functions of the API between two versions. If the signatures are equivalent, increment the patch version. If there are new signatures, but the existing ones are the same, it’s a minor version. If any function signatures change, it’s a major version.
Then you also need to examine trait impls and such but the basic idea is the same.
That oversimplifies and misses a lot of edge cases, such as:
- change the meaning of an existing parameter - e.g. an Integer timeout changes from seconds to milliseconds
- dependency changes, and this package exposes exposes types from that dependency
- internal refactor changes the order of execution of existing uses (say, a scheduler change in an async library, or event order in a GUI library)
Each of those would be, imo, a breaking change, but an automated semver tool would probably mark them as patch releases. I could come up with more examples, but hopefully the point is clear.
Maybe it’s correct 90% of the time, but the last 10% of the time can be really impactful. I think there should be less sigma against major releases. If in doubt, mark it as a major release.
change the meaning of an existing parameter - e.g. an Integer timeout changes from seconds to milliseconds
Ideally you should change the type if you do such a thing, which would cause it to become a breaking change. In this specific instance, you should take std::time::Duration obviously.
dependency changes, and this package exposes exposes types from that dependency
I think that should be automatically detectable?
But yes you’re right, in general it’s not possible to detect all forms of semver changes. But perhaps at least detecting violations when they weren’t meant to be there would be good.
And yea 100% agree with you, people should use the power that is 2.0.0 way more than they currently do.
Ideally you should change the type if you do such a thing
But that’s not always possible or desirable. For example, maybe you’re largely just passing it through to another library, and that library made a breaking change.
So I don’t think we should have semver always handled automatically, it should instead prompt the developer with its best guess, and the developer would ideally only move from patch -> minor, patch -> major, or minor -> major, and never the other direction. But the developer should always be involved in picking the version. So don’t just throw it into CI and call it a day, but instead have a CLI tool that suggests it and requires developer approval before making the PR for the version bump.
