PR: Fix issue getting user environment variables on Posix systems and pass them to the IPython console

[mrclary]

Description of Changes

• Use a shell script in Spyder's config directory to retriev user environment variables on posix systems.
• The shell script is created on Spyder startup and only for posix systems.

To get user environment variables from login and interactive startup files on posix, both -l and -i flags must be used. Parsing the environment list is problematic if the variable has a newline character, but Python's os.environ can do this for us. However, executing Python in an interactive shell in a subprocess causes Spyder to hang on Linux. Using a shell script resolves the issue. Note that -i must be in the sha-bang line; if -i and -l are swapped, Spyder will hang.

Also note that for environment variables for KernelSpec objects are first set to the user's environment variables, then updated with os.environ. Thus user login and interactive variables are ensured to be present, but values in os.environ may override user variable values.

Issue(s) Resolved

Part of #3891

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[ccordoba12]

Thanks @mrclary for your work on this!

[ccordoba12]

Note: This doesn't completely solve issue #3891 because that would require adding a tab to the IPython console preferences so that users can add env vars without editing their bashrc or similar files.

[mrclary]

Note: This doesn't completely solve issue #3891 because that would require adding a tab to the IPython console preferences so that users can add env vars without editing their bashrc or similar files.

I suppose this is a UX issue and maybe we could discuss it more at one of our dev meetings. I see a few additional ideas:

1. We could modify the user's ~/.bashrc, similar to how we add the aliases for the Linux installer. We could just delimit a section like conda does, e.g. >>> Spyder Injected Variables >>> ... <<< Spyder Injected Variables <<<, or similar. This would then provide similar functionality to the user environment variables widget as we have for Windows.
2. Alternatively, we could treat the user environment variables similar to how we manage the PYTHONPATH. We could show what is provided by the system, allow the user to add and/disable variables, but these don't get applied upstream to the system, only to downstream processes. The current Windows functionality does not conform to this, so maybe we consider changing it in this scenario.

[ccordoba12]

I suppose this is a UX issue and maybe we could discuss it more at one of our dev meetings

Agreed. We need to solve that in another PR.

Alternatively, we could treat the user environment variables similar to how we manage the PYTHONPATH.

I like this idea. That way the env vars managed by us would be propagated to the LSP, IPython console and all other things we run in external processes.

[ccordoba12]

Great work here @mrclary! I tested this locally and it's working as expected.