On Apple M1, Black often drops the ":9]=" out of f"{...[:9]=}", as Internal Error #4446
Description
Describe the bug
Black running on M1 MacBooks does drop a few Characters of Python Source Code, when given these particular 120 Characters, but only sometimes. Sometimes you call Black and it works. Sometimes you call, and it chokes
To Reproduce
Visit an M1 MacBook and feed these 4 Lines of Python Code into Black
For example, take these 4 Lines, formatted exactly as shown
import argparse
import string
S1 = f"{argparse.OPTIONAL[:9]=}"
S2 = (string.ascii_uppercase + string.ascii_lowercase)And try calling Black, more than once, on this same input with no arguments
black file.pyThe resulting error is:
INTERNAL ERROR: Black produced code that is not equivalent
It drops the : 9 ] = part of the F String Slice. Oops
Expected behavior
No Internal Error
Environment
- Black's version: 24.8.0 (compiled: yes)
- OS and Python version: Python (CPython) 3.12.5 at macOS 14.6.1 23G93 on Apple M1 Pro Chip inside MacBook Pro 16-inch, 2021
Additional context
Below is a Terminal transcript of reproducing this occasional Internal Error
Look closely and you'll see some runs on the same input fail like this, but some runs don't fail. This bug combines ( a ) that the results can and are inconsistent, and ( b ) that some of the results are Internal Errors
(PIPS) %
(PIPS) %
(PIPS) % cp -p p1.py p2.py && black p2.py
error: cannot format p2.py: INTERNAL ERROR: Black produced code that is not equivalent to the source. Please report a bug on https://github.com/psf/black/issues. This diff might be helpful: /var/folders/6j/yj_0gg5d7dg02zhp0vwfx0580000gp/T/blk_kyph83rd.log
Oh no! 💥 💔 💥
1 file failed to reformat.
(PIPS) %
(PIPS) % cat /var/folders/6j/yj_0gg5d7dg02zhp0vwfx0580000gp/T/blk_kyph83rd.log
--- src
+++ dst
@@ -34,11 +34,11 @@
values=
Constant(
kind=
None, # NoneType
value=
- 'argparse.OPTIONAL[:9]=', # str
+ 'argparse.OPTIONAL[', # str
) # /Constant
FormattedValue(
conversion=
114, # int
format_spec=
(PIPS) %
(PIPS) % cat p1.py
import argparse
import string
S1 = f"{argparse.OPTIONAL[:9]=}"
S2 = (string.ascii_uppercase + string.ascii_lowercase)
(PIPS) %
(PIPS) %
(PIPS) % cp -p p1.py p2.py && black p2.py
error: cannot format p2.py: INTERNAL ERROR: Black produced code that is not equivalent to the source. Please report a bug on https://github.com/psf/black/issues. This diff might be helpful: /var/folders/6j/yj_0gg5d7dg02zhp0vwfx0580000gp/T/blk_wzw1ae9e.log
Oh no! 💥 💔 💥
1 file failed to reformat.
(PIPS) %
(PIPS) % cp -p p1.py p2.py && black p2.py
reformatted p2.py
All done! ✨ 🍰 ✨
1 file reformatted.
(PIPS) %
(PIPS) % black --version
black, 24.8.0 (compiled: yes)
Python (CPython) 3.12.5
(PIPS) %
(PIPS) % md5sum p1.py
+ openssl dgst -md5 p1.py
+ tr '()=' ' '
+ awk '{print $3, $2}'
ee23bcabee4f1f5677c443bd6b4b2449 p1.py
(PIPS) %
This Bug only repros for me on my M1 MacBook
I've not found anywhere else where it will repro. I tried a Linux, but it didn't repro there. Every time I've tried it three times in a row at my M1 MacBook, I do repro 1 or 2 or 3 Failures
I first saw this go boom on 962 Lines
Thank you for believing I could help. Am I helping? Can I help more?