AttributeError calling subprocess.check_output(input=None) with encoding or errors args

[akulakov]

Bug report

subprocess.check_output(input=None) raises an AttributeError when called with encoding or errors args.

Example:

>>> check_output(['ls'], input=None, encoding='utf-8')
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 File "/Users/ak/opensource/cpython4/Lib/subprocess.py", line 466, in check_output
 return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 File "/Users/ak/opensource/cpython4/Lib/subprocess.py", line 549, in run
 stdout, stderr = process.communicate(input, timeout=timeout)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 File "/Users/ak/opensource/cpython4/Lib/subprocess.py", line 1206, in communicate
 stdout, stderr = self._communicate(input, endtime, timeout)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 File "/Users/ak/opensource/cpython4/Lib/subprocess.py", line 2035, in _communicate
 self._save_input(input)
 File "/Users/ak/opensource/cpython4/Lib/subprocess.py", line 2115, in _save_input
 self._input = self._input.encode(self.stdin.encoding,
 ^^^^^^^^^^^^^^^^^^
AttributeError: 'bytes' object has no attribute 'encode'. Did you mean: 'decode'?

Your environment

• CPython versions tested on: 3.12 (the issue is also present in 3.10 and 3.11)
• Operating system and architecture: MacOS M1, 11.5

I will create a PR a bit later today.

[gpshead]

thanks! That this bug has probably been present for so long I guess means people don't use this combination of args very often?

[akulakov]

I think input=None maybe isn't used much, and the workaround of input='' is not too hard to find.

Thanks for reviewing @gpshead @JelleZijlstra !