Remaining excess recompilation #3760
Description
General summary/comments (optional)
Following resolution of #3732, there is still some unnecessary recompilation going on in some situations, as noted in the PR #3750. Not sure if this will be resolved by per component builds, or whether it should be attacked in the meantime, so I thought I'd note it in this issue. It seems to me the solution will require some reworking of constructPlan. I'm happy to take a look at it but if you think it's more appropriate for somebody else that's fine too!
Steps to reproduce
Have a project with 2 packages where bar depends on foo. Compile foo with tests (e.g. stack build foo:foo-test bar). Edit a foo test module is edited bar will be unregistered and recompiled.
Expected
foo's test suite is recompiled but no action for bar is necessary.
Actual
bar will also be unregistered and recompiled, despite the fact that none of the code that it depends on changed.
Stack version
Local build of branch for the fix for #3732.