Add failing test for pre-release and backtracking behavior #3038
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Hi, I have been spending a lot of time on a Rust port of pubgrub and stumbled upon a tricky case regarding handling of pre-releases and backtracking behavior. In particular, due to the creation of
NoVersions
incompatibilities potentially preventing the selection of a pre-release version after backtracking.So I've checked how pub handles this by adding a test and it seems that pub fails to solve dependencies in that situation. Here is the test I've added:
It consists of putting the solver on the wrong track by making it pick
a 1.1.0
followed byb 1.0.0
then realizing that there is no compatiblec
. At that moment, it should backtrack and remember the wrong decision withNoVersions
incompatibilities. The issue is that it seems to create knowledge preventing it to pick theb 1.1.0-alpha
pre-release while it's a totally valid version after backtracking.What are your thoughts on this?