specify environment variables in run()

[philtay]

Ref: #259

Tests and docs after your approval and first round of comments.

[betterdiff]

• E501 line too long (82 > 79 characters)

[philtay]

Don't know exactly why the tests fail. On my PC tox doesn't report any problem. Anyway, please find below a simple task that shows the feature.

from invoke import run, task

@task
def foo():
    run("env")
    print "************************************************************"
    run("env", env={'FOO':'BAR'})
    print "************************************************************"
    run("env", env={})

[sophacles]

This is a pretty big breaking change to current (and arguably expected) behaviour. If the user doesn't pass an environment, the child process is executed with no environment (empty dict). The general expected behaviour is that a child is spawned with the environment of it's parent unless otherwise specified.

This would probably be best as:

 # Environment variables
self.env = os.environ.copy()
if env:
    self.env.update(env)

[philtay]

@sophacles thanks for your feedback. if the user doesn't pass an environment the child process is executed WITH the parent's environment. there is no breaking change. only if the user passes an empty dict the child process is executed with no environment.

my implementation is:

• non empty dict -> add these vars to the current env and execute the process
• empty dict (or something else that evaluates to False in boolean context) -> execute the process with no env
• if the user doesn't pass an env (or None) -> execute the process with the parent's env (i.e. current behavior)

[sophacles]

@philtay Oh got it, I was a bit confused on that chunk of code. I understand the logic now - thanks for the clarification

Thinking further about it - I think perhaps the best thing to do would be mirror the subprocess environment logic, that is:

                           # from subprocess.py line 1281 in python 2.7.10
                            if env is None:
                                os.execvp(executable, args)
                            else:
                                os.execvpe(executable, args, env)

Using values from os.environ should be left to the user to set up: there are too many edge cases otherwise:

• user wants to remove some variables from os.environ
• user wants to only have a specific environment (note Allow arbitrary shells #67 will also need to be completed before this case is fully available - setting shell to something like /bin/env -i /bin/bash) or alternately a runner with shell=False available.
• etc

[sophacles]

Tangentially related to my comment above: the invoke code has:

                # TODO: also see if subprocess is using equivalent of execvp...

@bitprophet - the answer to this todo is: yes, subprocess uses execvp and execvpe when not on windows.

[philtay]

@sophacles i agree with you. i'll wait for @bitprophet input before making changes.

[bitprophet]

Went ahead with my own version of this today (necessitated by interim changes); credited in changelog though. Thanks!