crash with the wrong number of spaces before a type-comment for a typed-function

[15r10nk]

Black f7174b

Playground link

Options

--line-length=88
--safe

Input

def name_4[**name_0](): # type: ignore
    pass

Output

cannot use --safe with this file; failed to parse source file AST: invalid syntax (<unknown>, line 1)
This could be caused by running Black with an older Python version that does not support new syntax used in your source file.

Expected

black should be able to format the code.
The problem is the number of spaces before the #.
There is no problem with two spaces before # or if --fast is used.

This works:

def name_4[**name_0]():  # type: ignore
    pass

[JelleZijlstra]

I can't reproduce this locally running Black with Python 3.12. The --safe check relies on ast.parse and therefore only works with syntax understood by the host Python, even if Black's parser can understand the syntax.

When you run this code on Black running on Python < 3.12, you'll see that it succeeds only if Black won't make any changes to the code:

% python -m black --version
python -m black, 23.10.1 (compiled: no)
Python (CPython) 3.11.1
% python -m black -c '''def name_4[**name_0]():               
    pass
'''
def name_4[**name_0]():
    pass

But fails if Black does change the code:

% python -m black -c '''def name_4[**name_0]( ):
    pass
'''
def name_4[**name_0]( ):
    pass
error: cannot format <string>: cannot use --safe with this file; failed to parse source file AST: expected '(' (<unknown>, line 1)
This could be caused by running Black with an older Python version that does not support new syntax used in your source file.

That's because Black skips the safety check if it didn't change anything, on the assumption that its input code is already safe.

[15r10nk]

Yes you are right. I used locally black which was installed with pipx on 3.11.

I believed that it was a bug because I could reproduce it in the online playground.