UP028 false positive when a target variable is global or nonlocal #16445
Description
Summary
The fix for yield-in-for-loop (UP028) is incorrect when the for loop’s target list includes a global or nonlocal variable. Rewriting the loop with yield from means the variable isn’t updated. This is similar to #15725. The fix is already marked unsafe, but because in this context it is so likely to break the program, no fix should be provided.
$ cat >up028.py <<'# EOF'
CURRENT_ELEMENT = None
def f(iterable):
global CURRENT_ELEMENT
for CURRENT_ELEMENT in iterable:
yield CURRENT_ELEMENT
list(f("xyz"))
print(CURRENT_ELEMENT)
# EOF
$ python up028.py
z
$ ruff --isolated check --select UP028 up028.py --unsafe-fixes --fix
Found 1 error (1 fixed, 0 remaining).
$ cat up028.py
CURRENT_ELEMENT = None
def f(iterable):
global CURRENT_ELEMENT
yield from iterable
list(f("xyz"))
print(CURRENT_ELEMENT)
$ python up028.py
NoneVersion
ruff 0.9.9 (091d0af 2025-02-28)