I have a question about

mypy

and how

pants

is using it. We are using

mypy

with protobufs (with

mypy-protobuf

, so it generates

pyi

files). But

pants check

, using

mypy

will actually output errors about the

pyi

files, which is not something we want. The issue is that

mypy

follows files, and it follows any imports that it can find in

MYPYPATH

. Which the generated protobuf files have to be in, otherwise other errors happen. But anything in

MYPYPATH

is considered fair game for following and checking. But if I understand how

pants

is working, it is just running

mypy

individually on each target, so I think there's no need to follow anything - essentially

pants

takes care of making sure our codebase is covered instead. So we can solve the problem of

mypy

analyzing

pyi

files by passing in

--follow-imports=skip

, but that's strongly discouraged by

mypy

documentation. However, in this case, with

pants

, I think it's the right thing to do. Is this way of thinking reasonable?

I think so. I mean, does it work if you do?

It does work, yes (at least when I reproduce on the command line). Thanks for confirming

Well the generated files aren't ever materialized in your repo, so the glob is immaterial

@happy-kitchen-89482, what controls what files Pants is feeding to

mypy

for processing? I was expecting it to be controlled by the glob, but as you say, maybe by the time we're in the sandbox, the glob has already done its work and is not useful anymore. There may not be a difference between the command-line vs not. I'm testing the command-line of a file that uses the protobufs that have the

pyi

files, and my command-line run for that file is successful. However, my success means nothing if Pants is actually also calling

mypy

on the

pyi

files (or doing the equivalent via the

mypy

daemon).

What controls the files Pants feeds to mypy is what you specify on the command line. The

globs

in BUILD files just group files together for the purpose of applying target metadata to them (and if you add an explicit dependency on the target then that's as if you added one for each of the files in the target)

Thank you, will definitely do that and report back!

Ooof

@happy-kitchen-89482 exactly!

I feel like Pants could work around that somehow

I'll see what I can figure out; it isn't obvious right now what Pants could be doing here. My only thought is maybe autogenerating the per-module mypy configs that were one of the workarounds, but that seems dangerous. Or, more in the realm of pure hacks, inserting that mypy ignore-errors bit manually for every

pyi

file

mypy-protobuf

generates.

We run mypy by passing it a list of newline-separated input files with

@__files.txt

. I have a feeling that we put those generated files in that list, and we shouldn't.

Yes, I did see those, but it looked correct. It did not include pyi files.

Huh, OK, so Pants is doing the right thing