If version 0.7 turned out to hit the right API and not require backward incompatible changes, releasing a version 1.0 would be as disruptive as a major version change to your users and communicate through version semantics that it is a breaking change.
Semver declares that version 0.x is for initial development where there is no stability guarantee at all. This is the right semantics for a versioning system, but Cargo doesn't follow this part of semver. Providing stability guarantees throughout the 0.x cycle inevitably results in projects getting stuck in 0.x.
This is one of my biggest gripes with Cargo. But Rust people seem to universally consider it a non-issue so I don't think it'll ever be fixed.
That’s a feature of semver, not a bug :)
Long answer: You are right to notice that minor versions within a major release can introduce new APIs and changes but generally, should not break existing APIs until the next major release.
However, this rule only applies to libraries after they reach 1.0.0. Before 1.0.0, one shouldn’t expect any APIs to be frozen really.
> Major version zero (0.y.z) is for initial development. Anything MAY change at any time. The public API SHOULD NOT be considered stable.
Cargo is explicitly breaking with Semver by considering 0.3.5 compatible with 0.3.6.
In practice, there's no real issue with using the first non-zero component to define the group of API-compatible releases and most package managers agree on the semantics.
Eventually this will get cleared up. I’m close than I’ve ever been to actually handling this, but it’s been 9 years already, so what’s another few months…
Nope, this is what the semver trick is for: https://github.com/dtolnay/semver-trick
TL;DR: You take the 0.7 library, release it as 1.0, then make a 0.7.1 release that does nothing other than depend on 1.0 and re-export all its items. Tada, a compatible 1.0 release that 0.7 users will get automatically when they upgrade.
Even more interesting is that you can use this to coordinate only partially-breaking changes, e.g. if you have 100 APIs in your library but only make a breaking change to one, you can re-export the 99 unbroken APIs and only end up making breaking changes in practice for users who actually use the one API with breaking changes.
Such a stupid state of affairs.
If you didn't want people to depend on your package (hence the word "dependency") then why release it? If your public interface changes, bump that major version number. What are you afraid of? People taking your project seriously?
1.x communicates (to me at least) you are pretty happy with the current state of the package and don't see any considerable breaking changes in the future. When 2.x comes around, this is often after 1.x has been in use for a long time and people have raised some pain points that can only be addressed by breaking the API.
Because this comment, "The project is still in development, it might be stable enough for use in "real projects(tm)", but it might also still significantly change." That describes every project. Every project is always in development. Every project is stable until it isn't. And when it isn't, you bump the major number.
Nobody cares that Chrome's major version is 147.
By releasing a library with version 0.x, I communicate: "I consider this project to be under initial development and would advice people not to depend on in unless you want to participate in its initial development".
I don't understand why people find this difficult or controversial.
For example, sometimes projects that have a 0.y version get depended on a lot, and so moving to 1.0.0 can be super painful. This is the case with the libc crate in Rust, which the 0.1.0 -> 0.2.0 transition was super painful for the ecosystem. Even though it should be a 1.0.0 crate, it is not, because the pain of causing an ecosystem split isn't considered to be worth the version number change.
The only time you run into a problem is if you try and use values with a type from 0.1 with a function that takes a 0.2 as an argument, or whatever. Then you get a type error.
Easy, just add bloat code so it will use 5GB of RAM by default, that's instant adoption by MS.