gh-129707: Check Tools/build/compute-changes.py with mypy

[sobolevn]

There was one error locally:

» mypy --config-file Tools/build/mypy.ini Tools/build/compute-changes.py:90: error: Incompatible return value type (got "frozenset[Path]", expected "set[Path]") [return-value] return frozenset(map(Path, filter(None, map(str.strip, changed_files)))) ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Found 1 error in 1 file (checked 2 source files) 

• Issue: New compute-changes.py should be checked with mypy #129707

[AA-Turner]

Please use Set rather than the concrete class.

A

[bedevere-app]

When you're done making the requested changes, leave the comment: I have made the requested changes; please review again.

[AA-Turner]

Can we make this a multi-line list? Ideally we could use a TOML file, does MyPy support mypy.toml or .mypy.toml?

[sobolevn]

It supports pyproject.toml, but it can affect stuff. + Our CI expects all folders to have mypy.ini. Current version of mypy does not support multiline strings here. But, I will fix that upstream. So, we can expect this in 1.16.0 somewhere.

[hugovk]

Seems to work like this?

Suggested change

	files = Tools/build/generate_sbom.py, Tools/build/compute-changes.py
	files =
	Tools/build/compute-changes.py,
	Tools/build/generate_sbom.py

(Unfortunately can't add a trailing comma to the last entry.)

[AA-Turner]

I've created a MyPy issue to request support for mypy.toml or similar: python/mypy#18617

[sobolevn]

I will fix it shortly, sorry for the , bug 😢
I've fixed it several times already, but it is very persistent for some reason.

[sobolevn]

I don't quite agree about the Set change, since we work with concrete types in our conrete case, but I won't debate about it :)

[AA-Turner]

I don't quite agree about the Set change, since we work with concrete types in our conrete case

True! My rationale is that it might make sense in some future change to use set internally rather than frozenset in some functions, but the only interface we promise is a non-mutable set. We could perhaps even change to Iterable[Path], as we only iterate over the collection at present.