Invoke: Allow arbitrary shells

[brejoc]

Make sure users can determine which local shell is used when executing commands.

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Was: _Only Bash as shell?_

I've only had a quick peek at the code, but I think the bash shell is hardcoded in the runner. Would be nice to let the user define the the shell in tasks.py, since some shells don't share the same syntax.

[bitprophet]

That's totally on the roadmap, yea. I'll mutate this issue's title/desc to reflect that it's an intended line item, so to speak :) Thanks!

[bitprophet]

N.B. this is only hardcoded in one spot, invoke/runner.py; it shows up in our vendorized pexpect but all of those bash mentions are in docstrings, so not a problem.

[brejoc]

Yes, that was the place I saw it. The best place to make this editable would be the tasks.py in my opinion. What do you think? Just like make does it:

SHELL := /bin/bash

[bitprophet]

I've been working up to actual config, my general idea is like so:

• Bottom level is a run kwarg, like echo and friends, so it can be overridden per-execute in any use case.
• Mid level is a Context object which acts as a config holder & allows one to pass configs around.
  
  
  
  • This is implemented, though the "edit it at the Python level" angle isn't beautiful - it's just dict attributes on Context objects, and I need to figure out how best to 'merge' CLI level settings (below) with in-task-module settings (what you want).
  
  
• Top level is CLI options, i.e. inv --shell=/bin/zsh mytask. These require use of contextualized tasks to take effect - again see echo.

Adding a CLI flag is easy, just follow #32 / #27 re: --echo; having a useful task-module-level way of merging stuff might need more thinking.

[bitprophet]

Ran into an internal need for this in #152 (see final comment), so, poking now.

The tl;dr of current state of this issue:

• Configuration has been in for a long time now (this ticket is old) so not a problem
• PTY-driven run sets its own shell, which is /bin/bash, so that's easily updated
• non-PTY-driven run uses subprocess' own hardcoded default, /bin/sh, but that should be overrideable via the executable kwarg

[bitprophet]

All done. Simply configure run.shell via any config method, or say run('command', shell='/bin/fish') or whatnot at runtime.

[presidento]

Great, thank you @bitprophet!
(Didn't you want to add it to the 0.12.3 milestone?)

[frol]

Just for your info, the implementation of this feature breaks Invoke on Windows: #345.