Always use a sequence in args to subprocess.Popen()

[fridex]

According to docs, it is recommended to pass args as a sequence.

[fridex]

Without this fix I'm experiencing the following issue:

In [1]: import delegator

In [2]: delegator.run(['echo', 'hello']).out
Out[2]: '\n'

In [3]: 

According to docs (see args section):

Unless otherwise stated, it is recommended to pass args as a sequence. On POSIX, if args is a string, the string is interpreted as the name or path of the program to execute. However, this can only be done if not passing arguments to the program.

[fridex]

ping @kennethreitz, any change to get this reviewed/in? thanks!

[timofurrer]

@fridex do you mind resolving the merge conflicts to get a step further to know if this can/should be merged?

[fridex]

@timofurrer done, thanks for refresh.

[timofurrer]

Awesome, @fridex - thanks. Can you have a look at the feedback from @akshaykumar90.

[fridex]

The reason your code example above doesn't work is the shell argument being set to True in _default_popen_kwargs. Further below in the docs:

The shell argument (which defaults to False) specifies whether to use the shell as the program to execute. If shell is True, it is recommended to pass args as a string rather than as a sequence.

This is because

If args is a sequence, the first item specifies the command string, and any additional items will be treated as additional arguments to the shell itself.

This translates to the following code in your example, and a bare echo is run which correctly returns '\n'.

Popen(['/bin/sh', '-c', 'echo', 'hello', ...])

That's is true - but this is based on the internal behavior relying on how delegator.py is implemented. Following my example:

In [1]: import delegator

In [2]: delegator.run(['echo', 'hello']).out
Out[2]: '\n'

I would expect "hello" to be printed relying solely on delegator's API (as a consumer of delegator library).