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by jesseryoung
1838 days ago
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"Don't change the function signature" and semver are things that are absolutely hammered into devs who work on library code. I'd be hard pressed to find somebody even tangentially involved in software development who doesn't understand this. Semver doesn't cover changes in behavior. What a "breaking change" is when it comes to behavior changes is up to the person who implemented it. |
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It does:
https://semver.org/
"Software using Semantic Versioning MUST declare a public API. This API could be declared in the code itself or exist strictly in documentation. However it is done, it SHOULD be precise and comprehensive."
If the API changes semantics between different releases, it is a breaking change. It does not matter whether the types in the function signature is identical. If
prints a report in version 1.0, and deletes the database or launches nuclear weapons in version 1.1, it does not follow semantic versioning.But the core problem with semantic versioning is that it somehow legitimizes to make breaking changes all the time. It is not OK to beat somebody up in a bar. It is also not OK to tell somebody that he is going to be beaten up, and then beat him up.
Now, semantic versioning holds the idea that it is OK to make breaking changes, if only you tell people before. And this is a lousy idea. Breaking changes break other people's code, especially if they use it in deep graphs of dependencies. And they can't necessarily do anything about it, because they might have two dependencies which are depending on your library, only that the first one now requires version 2.0 at least, while the second one will not work with anything newer than version 1.99.17. And thus the whole project is broken. Actually, requiring the new version 2.0 in the first dependency is a breaking change, too, because it breaks backwards-compatibility.
And this is something which the Python devs just did not comprehend - that this kind of breakage trickles up dependency graphs and makes it extremely difficult for users with a limited budget to make upgrades, even if most of their features are highly desired.