Fixes xargs partition length on Windows for EXE hooks

[amarvin]

Closes #3124

[asottile]

I don't think this is the right fix or really the problem

I've verified the length computation is correct on my windows machine so something is different about yours (and it's not this)

you'll need to do some more debugging on your end too figure out what's happening

and usually when the length is exceeded there's an error. if that's not happening there's likely something else at play!

[amarvin]

Can you confirm that in your system the pretty-format-json hook in pre_commit.xargs.xargs() gets shebang normalized to a .bat or .cmd file? For me:

> cmd[0]
'C:\\Users\\alexm\\.cache\\pre-commit\\repodli143ao\\py_env-python3.12\\Scripts\\pretty-format-json.EXE'

so then _max_length stays at the default of 30720, which is too long for Windows batch file lines.

[asottile]

batch is not in play on my system, no

[amarvin]

Huh? All I'm saying is that on my system Windows 11, this if-statement is never entered:

because for pretty-format-json, it's an EXE

[amarvin]

The length of the first command sent to cmd_fn was 15440 characters. I can't even paste that long of a string into cmd.exe.

[amarvin]

You're right that neither batch files nor cmd.exe are being used in this case / on my system by the subprocess.Popen() in pre_commit.util. Not sure where this differing behavior is coming or why shorting the partitioning max length fixes it.

[asottile]

yes that's why I'm saying you need to do some debugging to figure out why. I'm not blindly changing the code