This ticket asks FESCo to consider whether the new ty package should be granted a permanent exception under the Updates Policy.

The ty Python type checker and language server is built from the same Rust sources as the ruff linter and formatter, which already has such an exception, and the implementations are tightly entangled, but the version schemes and the release schedules are independent. While ruff has been popular for some time, ty was only recently announced as ready for “beta” usage by early adopters.

Although ty is still in rapid and relatively early development, we can expect from the example set by ruff and uv (also developed by Astral) that breaking changes will be relatively small and well-considered rather than disruptive and haphazard. Indeed, from ty 0.0.1 to 0.0.15, there has so far been only one documented breaking change: a single diagnostic rule was renamed in 0.0.8, affecting people who had it in their suppression files.

It’s my opinion that the risk and inconvenience posed to Fedora users by these occasional small breaking changes will be consistently outweighed by the benefits of new features and bugfixes, including support for new Python language versions. This is especially true considering that ty will primarily be used directly by developers rather than as a dependency for other distribution packages. This is basically the same rationale as for other Python development tools that were already granted similar exceptions, like ruff, uv, and tox and black (previously, previously).

If this exception is granted, ty package maintainers may still choose to keep an old version in certain branches – for example, if the branch is near its end-of-life date, or if the breaking changes in a new version appear too disruptive – and the usual care should be taken to avoid impacting any Fedora packages that do end up depending on ty.