We have an audit that checks each formula's dependency tree for multiple
versions of the same software. We have an allowlist that allows us to
ignore this audit, but this allowlist requires each formula with a
conflict in its dependency tree to be listed there.
Here, I propose the reverse: if formula `foo` appears in the
`versioned_formula_dependent_conflicts_allowlist`, then all its
dependents will not fail the versioned dependencies conflict because of
a conflict with formula `foo`.
I'd like to do this in the case of `python`, where I think the versioned
dependencies conflict check hurts us more than helps us. Versioned
dependency conflicts are most problematic in the case of libraries with
the same install name but incompatible ABIs. This is almost never a
problem with Python: almost no formulae link with the Python framework
on macOS (in part due to one of our audits that disallows Python
framework linkage in Python modules). Moreover, the various Python
frameworks that we ship have the version in the install name.
The above _might_ be a problem on Linux, since we allow unrestricted
linkage with `libpython`. However, we don't even check versioned
conflicts on Linux, so we aren't as concerned about this in the first
place.
This is also a lot more convenient than adding the dependents of some
Python formula one by one as they acquire conflicts due to changes in
other formulae.
I've also amended `tap_auditor` to allow the use of formula aliases in
an allowlist, to allow us to add `python` to this allowlist instead of
each individual versioned Python formula.
See also discussion at Homebrew/homebrew-core#108307.
