Black cannot parse list unpacking

[ThGaskin]

Describe the bug

The following snippet blocks git commits:

    # Get the counts and the bin centres
    counts, bin_centres = np.take(res, 0, axis=axis), np.take(res, 1, axis=axis)
    sel = [0] * len(np.shape(bin_centres))
    sel[axis] = None
    bin_centres = bin_centres[*sel].flatten() # <---- Error!

with error

error: cannot format model_plots/data_ops.py: Cannot parse: 462:30:     bin_centres = bin_centres[*sel].flatten()

• Black's version: black==23.10.1
• OS and Python version:macOS Ventura 13.4.1, Python 3.11.6

[JelleZijlstra]

Note this is new syntax in Python 3.11, introduced by PEP 646. See python/cpython#31018 for the Python grammar changes; we'll need something similar.

[hauntsaninja]

I cannot reproduce. Black already fully supports PEP 646 as far as I can tell, see https://github.com/psf/black/pull/3071/files/ Are you sure you're using 23.10.1?

λ cat xx.py
counts, bin_centres = np.take(res, 0, axis=axis), np.take(res, 1, axis=axis)
sel = [0] * len(np.shape(bin_centres))
sel[axis] = None
bin_centres = bin_centres[*sel].flatten() # <---- Error!

λ python -m black xx.py --check --diff
--- xx.py	2023-10-26 05:26:40.021527+00:00
+++ xx.py	2023-10-26 05:30:33.375899+00:00
@@ -1,4 +1,4 @@
 counts, bin_centres = np.take(res, 0, axis=axis), np.take(res, 1, axis=axis)
 sel = [0] * len(np.shape(bin_centres))
 sel[axis] = None
-bin_centres = bin_centres[*sel].flatten() # <---- Error!
+bin_centres = bin_centres[*sel].flatten()  # <---- Error!
would reformat xx.py

Oh no! 💥 💔 💥
1 file would be reformatted.

[henriholopainen]

Also can't repro.

% black --version
black, 23.10.1 (compiled: no)
Python (CPython) 3.11.3
% black --diff t.py
--- t.py	2023-10-27 09:11:03.653578+00:00
+++ t.py	2023-10-27 09:11:04.873324+00:00
@@ -1,5 +1,5 @@
 # Get the counts and the bin centres
 counts, bin_centres = np.take(res, 0, axis=axis), np.take(res, 1, axis=axis)
 sel = [0] * len(np.shape(bin_centres))
 sel[axis] = None
-bin_centres = bin_centres[*sel].flatten() # <---- Error!
+bin_centres = bin_centres[*sel].flatten()  # <---- Error!
would reformat t.py

All done! ✨ 🍰 ✨
1 file would be reformatted.

[JelleZijlstra]

Also can't reproduce, so closing.

It's possible there's another syntax issue later in the file that makes Black try falling back to a grammar without PEP 646 support, though I can't reproduce that either.

[ThGaskin]

The error occurs when committing via git:

sort imports.............................................................Passed
black code formatting....................................................Failed
- hook id: black
- exit code: 123

error: cannot format model_plots/data_ops.py: Cannot parse: 383:34:         bin_centres = bin_centres[*sel].flatten()

Oh no! 💥 💔 💥
6 files left unchanged, 1 file failed to reformat.

check RST backticks..................................(no files to check)Skipped
fix end of files.........................................................Passed
fix trailing whitespace..................................................Passed

When I run black path/to/file it reformats the file just fine.

[henriholopainen]

@ThGaskin is the pre-commit hook running a different version/configuration of black? Could you share the full file file or try to isolate the issue and share a minimal snippet where it reproduces?