Allow use ~/ in the kernel's command or it's arguments

[svetlyak40wt]

After this patch you'll be able to do this
in a kernel spec:

{
    "argv": ["~/the-project/jupyter/kernel/run", "-f", "{connection_file}"],
    "display_name": "The Project (dev)",
    "language": "python"
}

This can be useful when you are installing kernel with --user option
into /home/my-name/.local/share/jupyter/kernels/ and having your jupyter
notebooks in different subdirectories of ~/the-project/ folder.

In this case kernel for each notebook is started in the notebook's
subdirectory and without ~/ in the spec Jupyter is unable to find a
file for running a custom kernel.

[davidbrochart]

Thanks for the PR!
Does it mean every part of the command is treated as a potential path? Isn't there a chance we change something that was not a path?

[svetlyak40wt]

os.path.expanduser expands ~ only at the beginning of the string:

In [1]: import os.path

In [2]: os.path.expanduser('~/bin')
Out[2]: '/Users/art/bin'

In [3]: os.path.expanduser('Some~/bin')
Out[3]: 'Some~/bin'

In [4]: os.path.expanduser('Some~/bin~')
Out[4]: 'Some~/bin~'

There is only a very small probability that somebody will create a command-line program which wants arguments like ~some not being path names.

[davidbrochart]

Thanks!

[svetlyak40wt]

👍