I'm convinced making

str

also an

Iterable[str]

in typing-land is dangerous. We've had a long-standing bug in our graph traversal algorithm (for secondary ownership) it seems... With that hint, can you find the bug? https://github.com/pantsbuild/pants/blob/b7dee2e576beb5a49790cf5c1803418624631c1a/src/python/pants/engine/internals/graph.py#L904 (Answer in 🧵 )

Is someone setting

OwnersRequest.sources

to a str?

Inside of:

for secondary_owner_field in secondary_owner_fields:
                matching_files.update(
                    *secondary_owner_field.filespec_matcher.matches(list(sources_set))
                )

We're unpacking a list of strings.

set.update

takes

*s: Iterable[T]

, meaning we're updating it with each character...

I'd agree, with iterables of iterables, I generally don't follow my same typing conventions (for better or worse)

Oh uh, good job Google

this is a design mistake in python imo, the lack of a char type