Action space sampling returns invalid actions

[nicow-elia]

Environment

• Grid2op version: 1.9.3
• System: ubuntu16.04
• Additional system information

Bug description

When sampling from the action space and converting these actions into serializable dicts so they can be loaded from disc later, we will occasionally get results from the sort {"change_bus": {}} which is a do-nothing action and should be {}. Since grid2op 1.9, this type of action is not supported as input to the environment and raises an exception

How to reproduce

import grid2op

def test_action_space_sampling() -> None:
    env = grid2op.make("l2rpn_case14_sandbox")
    for _ in range(10000):
        act_dict = env.action_space.sample().as_serializable_dict()
        env.action_space(act_dict)

Current output

The test raises an exception

Expected output

The test succeeds.

[BDonnot]

Hello,

Thanks for spotting this. I fixed the issue in two different ways:

1. the as_serializable_dict() method will now discard the keys associated with "do nothing" (when nothing is modified for example)
2. the action will be nicer and accept "weird" do nothing actions such as env.action_space({"change_bus": {}})

I expect to release a new grid2op version next Monday (it's always a bad idea to release anything at all on Fridays)