Recommended way to forward arguments to commands

[rmorshea]

It'd like to know the recommended way to forward arguments to a command. For example, I have a test task that runs PyTest and I'd like to forward any extra arguments along to pytest. The best way I've found to do this is delimit my task's arguments from those of pytest with --. If I do this invoke seems to ignore all the following arguments. Ultimately this means I can do the following:

import sys
from invoke import task

try:
    EXTRA_ARGS = sys.argv[sys.argv.index("--") + 1: ]
except ValueError:
    EXTRA_ARGS = []

@task
def test(ctx):
    ctx.run(f"pytest {' '.join(EXTRA_ARGS)}"

Where usage could then be:

invoke test -- test_something.py::test_feature --maxfail=2 

While this works, I searched through the documentation and even a bit of the code, but didn't see anything that would explicitly allow for this sort of "argument forwarding" pattern. Is this behavior intended or is there a better way to achieve this? If it is something that invoke intentionally supports, perhaps these extra args (everything following --) could be attached to the Context.

[rmorshea]

I've found the logic that allows this to work and tests which enshrine it. So this approach does seem safe.

[rmorshea]

Given that this seems to be a well defined behavior it would be neat if I could define a task like:

@task
def test(ctx, *remainder):
    ctx.run(f"pytest {' '.join(remainder)}"

[zed]

It does indeed work:

import shlex
from invoke import task
from invoke.main import program

@task(autoprint=True)
def forward_args(c):
    return shlex.split(program.core.remainder)

Example:

inv forward-args -- "a '1 2'"                                         
['a', '1 2']

It fails for fabric:

fab -c tasks -H localhost forward-args -- "a '1 2'"
...
fabric.exceptions.NothingToDo: Was told to run a command, but not given any hosts to run it on!