F821 Undefined name item when assigning a set comprehension in an if-clause

[kurellajunior]

import logging
from itertools import groupby


class MonocausalTransformer:
    for key, tuples in groupby([("a",1),("a", 2),("b",3)], lambda t: t[0]):
        if len(replacements := {item[1] for item in tuples}) > 1:
            logging.error("Multiple replacements for %s: %s", key, replacements)

When running ruff . --fix on the whole project it gives this error message: F821 Undefined name `item`
But it works just as expected when executed
And extracting the set to a separate variable a line above works also fine

$ ruff --version
ruff 0.1.7
$ ruff --fix item.py 
item.py:7:33: F821 Undefined name `item`
Found 1 error.

[tool.ruff]
target-version = "py311"
line-length = 120
select = ["ALL"]
ignore = [
    "A003",
    "ARG002",  # unused method arguments, e.g. when implementing an interface
    "D10",  # TODO: Add doc messages to public api, or make private
    "D203",  # Conflicting with D211
    "D213",  # Conflicting with D212
    "TD002", "TD003", "FIX002",  # TODO: Fix all todo comments
    "PLC1901",  # We have to distinguish between None and ""
    "RUF012",  # Ignored already for pydantic models, but we use our own base class
    "S311",  # No cryptography happening here
]

https://play.ruff.rs/27d1104c-b86e-45dc-98c6-fc6eac195bcb

[charliermarsh]

Thanks! Does look like a bug.

[charliermarsh]

Is this the complete snippet? I'm unable to reproduce in the playground: https://play.ruff.rs/dd91b36b-c177-4e84-b190-368de569f6a4

[kurellajunior]

Is this the complete snippet? I'm unable to reproduce in the playground: play.ruff.rs/dd91b36b-c177-4e84-b190-368de569f6a4

You are right, I extracted only a small snippet, thought it was enough. I extracted now a larger snippet, stripped it down to the actual minimum: https://play.ruff.rs/27d1104c-b86e-45dc-98c6-fc6eac195bcb
This now gives on my console, in my poetry environment with ruff 0.1.7 the documented error:

$ ruff --fix item.py 
item.py:26:33: F821 Undefined name `item`
Found 1 error.

As soon as I remove the class context, the error is gone

Also, when I put everything inside __init__() the error is gone

Also updated the original post

[charliermarsh]

Thanks! Assume this has to do with accessing from within a class scope. We will fix.