Adding filter to system prune

[dvizzini]

I also updated the documentation.

I could not find any tests to modify. Are there any?

[dvizzini]

Just realized this PR has an issue:

$ docker system prune --all --volumes --filter "until=1680h"
ERROR: The "until" filter is not supported with "--volumes"

Where can I write unit tests that address this scenario?

[gabrieldemarmiesse]

First of all, thank you for the PR that's great :)

You can add tests in this file: https://github.com/gabrieldemarmiesse/python-on-whales/blob/master/tests/python_on_whales/components/test_system.py

Currently we don't have any tests for docker.system.prune() but I would be happy if we could have some.
You can simply create some objects (containers, pulling images, creating volumes), run the prune command and then check that those objects aren't there anymore.

If you need help, don't hesitate to ask!

[dvizzini]

Thank you! For one thing we need a --force in the command argument. This will hang as currently implemented. I will add that to the PR.

[gabrieldemarmiesse]

I believe too many pieces of code can throw a DockerException. It might hide a real bug in the test. Can you try to make the try:... Except: narrower? Or you could create the network with a random name, meaning that it won't have any effect if, by chance, the prune doesn't remove it. So you don't need the with statement.

[dvizzini]

Good point about this being too broad.

I don't quite understand what you are talking about with the random name. I create the network with random_name.

I'll think of a way to make this work.

[gabrieldemarmiesse]

Sorry, I wasn't clear. What I meant was that since the network has a random name, you don't need to delete it, meaning that you don't need to use with, meaning that you don't need a try except

[dvizzini]

I was deleting it -- twice! Point taken that I don't need to worry too much about a network with a randomly generated name floating around.

I got rid of the context manager. I don't need to worry about __exit__ not being called because cleaning the network is exactly what this test tests, and as you point out this network is pretty harmless even if that test failed.

[gabrieldemarmiesse]

Thanks you for this great pull request! It's a really cool contribution!

[dvizzini]

@gabrieldemarmiesse Thank you for your review! I am happy python_on_whales is so well maintained.