subprocess.run throws exception when input and stdin are passed as kwargs

[aecant]

BPO	34886
Nosy	@gpshead, @serhiy-storchaka, @MojoVampire, @miss-islington, @remilapeyre, @aecant
PRs	bpo-34886: Fix subprocess.run handling of exclusive arguments #11727 bpo-34886: Fix subprocess.run handling of exclusive arguments #11727 bpo-34886: Fix subprocess.run handling of exclusive arguments #11727 [3.8] bpo-34886: Fix subprocess.run handling of exclusive arguments (GH-11727) #13916 [3.7] bpo-34886: Fix subprocess.run handling of exclusive arguments (GH-11727) #13917
Files	subprocess_run_bug.py: Minimal working example

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/gpshead'
closed_at = <Date 2019-06-11.04:55:33.824>
created_at = <Date 2018-10-03.18:50:38.319>
labels = ['3.7', '3.8', 'type-bug', 'library', '3.9']
title = 'subprocess.run throws exception when input and stdin are passed as kwargs'
updated_at = <Date 2019-06-11.04:55:33.810>
user = 'https://github.com/aecant'

bugs.python.org fields:

activity = <Date 2019-06-11.04:55:33.810>
actor = 'gregory.p.smith'
assignee = 'gregory.p.smith'
closed = True
closed_date = <Date 2019-06-11.04:55:33.824>
closer = 'gregory.p.smith'
components = ['Library (Lib)']
creation = <Date 2018-10-03.18:50:38.319>
creator = 'aecant'
dependencies = []
files = ['47847']
hgrepos = []
issue_num = 34886
keywords = ['patch', 'patch', 'patch']
message_count = 11.0
messages = ['327002', '327003', '327004', '327008', '327009', '327011', '334728', '345042', '345046', '345049', '345179']
nosy_count = 6.0
nosy_names = ['gregory.p.smith', 'serhiy.storchaka', 'josh.r', 'miss-islington', 'remi.lapeyre', 'aecant']
pr_nums = ['11727', '11727', '11727', '13916', '13917']
priority = 'normal'
resolution = 'fixed'
stage = 'commit review'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue34886'
versions = ['Python 3.7', 'Python 3.8', 'Python 3.9']

[aecant]

If input and stdin parameters are passed as keyword arguments to subprocess.run, an exception is thrown even if input and stdin are both None.

The exception is ValueError: stdin and input arguments may not both be used.

I attach a minimal working example of the bug

[serhiy-storchaka]

What is wrong with this?

[aecant]

subprocess.run('ls', input=b'', stdin=None) # this is ok

kwargs = {'input': b'', 'stdin': None}
subprocess.run('ls', **kwargs) # this throws exception

The two calls should have the same behaviour, but one throws exception and the other doesn't. I think the exception shouldn't be thrown, because stdin is None.

[MojoVampire]

I just tried:

    subprocess.run('ls', input=b'', stdin=None)

and I got the same ValueError as for passing using kwargs. Where did you get the idea subprocess.run('ls', input=b'', stdin=None) worked?

[MojoVampire]

The actual code receives input by name, but stdin is received in **kwargs. The test is just:

    if input is not None:
        if 'stdin' in kwargs:
            raise ValueError(...)
        kwargs['stdin'] = PIPE

Perhaps just change `if 'stdin' in kwargs:` to:

    if kwargs.get('stdin') is not None:

so it obeys the documented API (that says stdin defaults to None, and therefore passing stdin=None explicitly should be equivalent to not passing it at all)?

[aecant]

and I got the same ValueError as for passing using kwargs. Where did you get the idea subprocess.run('ls', input=b'', stdin=None) worked?

Sorry, the example was wrong. Both calls have the same behaviour.

so it obeys the documented API (that says stdin defaults to None, and therefore passing stdin=None explicitly should be equivalent to not passing it at all)?

The actual problem is this. The fix you propose works for me.

[remilapeyre]

I opened a PR with @josh.r proposed change.

[gpshead]

New changeset 8cc605a by Gregory P. Smith (Rémi Lapeyre) in branch 'master':
bpo-34886: Fix subprocess.run handling of exclusive arguments (GH-11727)
8cc605a

[miss-islington]

New changeset 6324ac1 by Miss Islington (bot) in branch '3.8':
bpo-34886: Fix subprocess.run handling of exclusive arguments (GH-11727)
6324ac1

[miss-islington]

New changeset 10b4fd9 by Miss Islington (bot) in branch '3.7':
bpo-34886: Fix subprocess.run handling of exclusive arguments (GH-11727)
10b4fd9

[gpshead]

thanks!