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Cannot format code with local variable name `match` in same line as match pattern matching expression

Open CelestialGuru opened this issue 2 years ago • 1 comments

Describe the bug

Take this code:

import re
match = re.match(r"(?P<grade>LD|MD|HD)(?P<material>AL|SS)", "HDSS")
match (match.group("grade"), match.group("material")):
    case ("MD" | "HD", "SS" as code):
        print("You will get here")

And run it with these arguments:

$ black file.py --target-version py310 # or --target-version py311

The resulting error is:

cannot format foo.py: Cannot parse: 3:0: match (match.group("grade"), match.group("material")):

Expected behavior

Sure, the local variable name should be something else, but it's valid python and Python will run it perfectly fine. If Python is cool with it, then black should support it. (Even if it's poor taste in variable names; valid Python should not break black)

Environment

  • Black's version: 22.12.0
  • OS and Python version: docker run -it --rm python:3.11 bash

Workarounds

Black works if you use a different variable name:

the_match = re.match(r"(?P<grade>LD|MD|HD)(?P<material>AL|SS)", "HDSS")
match (the_match.group("grade"), the_match.group("material")):
    case _:
        pass

This simply proves the issue is with the variable name being match.

Black works also if you refactor the code to separate the local variable match and the keyword match:

match = re.match(r"(?P<grade>LD|MD|HD)(?P<material>AL|SS)", "HDSS")
grade, material = match.group("grade"), match.group("material")
match (grade, material):  # local variable `match` not used here
    case _:
        pass

An interesting case where Black works with match in the same line is:

match re.match(r"(?P<grade>LD|MD|HD)(?P<material>AL|SS)", "HDSS").groups():
    case _:
        pass

CelestialGuru avatar Jan 09 '23 22:01 CelestialGuru

cc @isidentical

JelleZijlstra avatar Jan 09 '23 22:01 JelleZijlstra

I think #3950 fixed this. I'll send a PR with a regression test.

JelleZijlstra avatar Oct 28 '23 04:10 JelleZijlstra