Gymnasium/tests/envs/mujoco/test_mujoco_custom_env.py

__credits__ = ["Kallinteris-Andreas"]

import os
import warnings

import numpy as np
import pytest

from gymnasium import utils
from gymnasium.envs.mujoco import MujocoEnv
from gymnasium.error import Error
from gymnasium.spaces import Box
from gymnasium.utils.env_checker import check_env


class PointEnv(MujocoEnv, utils.EzPickle):
    """
    A simple mujuco env to test third party mujoco env, using the `Gymansium.MujocoEnv` environment API.
    """

    metadata = {
        "render_modes": [
            "human",
            "rgb_array",
            "depth_array",
        ],
    }

    def __init__(self, xml_file="point.xml", frame_skip=1, **kwargs):
        utils.EzPickle.__init__(self, xml_file, frame_skip, **kwargs)

        MujocoEnv.__init__(
            self,
            xml_file,
            frame_skip=frame_skip,
            observation_space=None,  # needs to be defined after
            default_camera_config={},
            **kwargs,
        )

        self.metadata = {
            "render_modes": [
                "human",
                "rgb_array",
                "depth_array",
            ],
            "render_fps": int(np.round(1.0 / self.dt)),
        }

        obs_size = self.data.qpos.size + self.data.qvel.size

        self.observation_space = Box(
            low=-np.inf, high=np.inf, shape=(obs_size,), dtype=np.float64
        )

    def step(self, action):
        x_position_before = self.data.qpos[0]
        self.do_simulation(action, self.frame_skip)
        x_position_after = self.data.qpos[0]

        observation = self._get_obs()
        reward = x_position_after - x_position_before
        info = {}

        if self.render_mode == "human":
            self.render()
        return observation, reward, False, False, info

    def _get_obs(self):
        position = self.data.qpos.flat.copy()
        velocity = self.data.qvel.flat.copy()
        return np.concatenate((position, velocity))

    def reset_model(self):
        qpos = self.init_qpos
        qvel = self.init_qvel
        self.set_state(qpos, qvel)

        observation = self._get_obs()

        return observation


CHECK_ENV_IGNORE_WARNINGS = [
    f"\x1b[33mWARN: {message}\x1b[0m"
    for message in [
        "A Box observation space minimum value is -infinity. This is probably too low.",
        "A Box observation space maximum value is -infinity. This is probably too high.",
        "For Box action spaces, we recommend using a symmetric and normalized space (range=[-1, 1] or [0, 1]). See https://stable-baselines3.readthedocs.io/en/master/guide/rl_tips.html for more information.",
    ]
]


@pytest.mark.parametrize("frame_skip", [1, 2, 3, 4, 5])
def test_frame_skip(frame_skip):
    """verify that custom envs work with different `frame_skip` values"""
    env = PointEnv(frame_skip=frame_skip)

    # Test if env adheres to Gym API
    with warnings.catch_warnings(record=True) as w:
        check_env(env.unwrapped, skip_render_check=True)
        env.close()
    for warning in w:
        if warning.message.args[0] not in CHECK_ENV_IGNORE_WARNINGS:
            raise Error(f"Unexpected warning: {warning.message}")


def test_xml_file():
    """Verify that the loading of a custom XML file works"""
    relative_path = "./tests/envs/mujoco/assets/walker2d_v5_uneven_feet.xml"
    env = PointEnv(xml_file=relative_path)
    assert env.unwrapped.data.qpos.size == 9

    full_path = os.getcwd() + "/tests/envs/mujoco/assets/walker2d_v5_uneven_feet.xml"
    env = PointEnv(xml_file=full_path)
    assert env.unwrapped.data.qpos.size == 9

    # note can not test user home path (with '~') because github CI does not have a home folder