Initial analysis of the codecov/patch code coverage issue:

@tmadlener From looking at the report diff, the red background color of the line number and the hover text of the 🛈 symbol left to the red line number indicates that Line 1420 is not covered by tests: https://app.codecov.io/gh/spack/spack/compare/27167/diff#D1L1420
Adding a test to run with spack unit-test would be needed to make it pass.
Since the new line is in def _get_overwrite_specs() I'm assuming a test which uses spack install --overwrite should cover it, and there are appear to be some, according to grep -r overwrite lib/spack/spack/test. Maybe you have an idea why none of them appears to cover that line (assuming everything else I see is correct).

If we're not able to figure out why the codecov is dropping, another option would be to avoid memoizing and just precompute the set of all specs we need to check. Something like:

def _get_overwrite_specs(self):
    specs_to_check = set()
    for dag_hash in self.concretized_order:
        root_spec = self.specs_by_hash[dag_hash]
        specs_to_check.update(root_spec.traverse(root=True))
    return [s for s in specs_to_check if self._spec_needs_overwrite(s)]

Since specs are appropriately hashable, that should eliminate the duplicate work that memoizing eliminated.

If we're not able to figure out why the codecov is dropping, another option would be to avoid memoizing and just precompute the set of all specs we need to check.

That sounds like an overall nicer solution in any case in my opinion. I will give that a go and see if it works.

Ah, I just realized why I went with the memoization. _spec_needs_overwrite calls itself as well to figure out if dependent packages need to be rebuilt because (dev) dependencies have changed. Only having the set that collects all specs upfront doesn't help because only the first layer of dependency tree walking is removed, but below that nothing changes.

I have not been able yet to come up with some clever changes to _spec_needs_overwrite yet, that would work without the memoization and still respect the dependencies.

I found an alternative solution that avoids memoizing internal function calls. In my testing it seems to be only slightly slower compared to the memoized version (order of roughly 10 %).

The basic principle now is:

• Get a unique list of all specs in the environment (i.e. root specs and their dependencies)
• Check which ones of those are dev builds and have changed w.r.t. to the installed version
• Use the list of changed dev build specs as input to the _spec_needs_overwrite function

This still does a bit more work than it would need to, but at least it skips the costly part of repeatedly going to the file system to check time stamps for the same files over and over again, as that is done only once now per each dev build package.

@tmadlener, the CI Pipeline failure seems to be from:

Error: Pipeline generation failed due to the presence of the following specs that are known to be broken in develop:
[email protected]%[email protected]cuda+examples+exercisesipo+openmprocm+sharedtests

raja might have been fixed by: 6f8fd5b

Just to be one the safe side: Maybe could to rebase this PR to the current develop? (Just rerunning the CI could work too, but maybe it's a good idea to also rebase it)