Adds testing to check_env that closing a closed environment doesn't raise an error (#564)

Co-authored-by: Quentin GALLOUÉDEC <gallouedec.quentin@gmail.com>
Co-authored-by: Quentin Gallouédec <45557362+qgallouedec@users.noreply.github.com>

gymnasium/core.py

@@ -185,6 +185,7 @@ class Env(Generic[ObsType, ActType]):
         """After the user has finished using the environment, close contains the code necessary to "clean up" the environment.
 
         This is critical for closing rendering windows, database or HTTP connections.
+        Calling ``close`` on an already closed environment has no effect and won't raise an error.
         """
         pass
 

gymnasium/envs/mujoco/mujoco_rendering.py

@@ -603,7 +603,7 @@ class MujocoRenderer:
 
     The class has two main public methods available:
     - :meth:`render` - Renders the environment in three possible modes: "human", "rgb_array", or "depth_array"
-    - :meth:`close` - Closes all contexts initialized with the rendere
+    - :meth:`close` - Closes all contexts initialized with the renderer
 
     """
 

gymnasium/utils/env_checker.py

@@ -321,3 +321,13 @@ def check_env(env: gym.Env, warn: bool = None, skip_render_check: bool = False):
             logger.warn(
                 "Not able to test alternative render modes due to the environment not having a spec. Try instantialising the environment through gymnasium.make"
             )
+
+    if env.spec is not None:
+        new_env = env.spec.make()
+        new_env.close()
+        try:
+            new_env.close()
+        except Exception as e:
+            logger.warn(
+                f"Calling `env.close()` on the closed environment should be allowed, but it raised an exception: {e}"
+            )

gymnasium/wrappers/env_checker.py

@@ -5,6 +5,7 @@ from copy import deepcopy
 from typing import TYPE_CHECKING
 
 import gymnasium as gym
+from gymnasium import logger
 from gymnasium.core import ActType
 from gymnasium.utils.passive_env_checker import (
     check_action_space,
@@ -39,10 +40,11 @@ class PassiveEnvChecker(gym.Wrapper, gym.utils.RecordConstructorArgs):
         self.checked_reset = False
         self.checked_step = False
         self.checked_render = False
+        self.close_called = False
 
     def step(self, action: ActType):
         """Steps through the environment that on the first call will run the `passive_env_step_check`."""
-        if self.checked_step is False:
+        if not self.checked_step:
             self.checked_step = True
             return env_step_passive_checker(self.env, action)
         else:
@@ -50,7 +52,7 @@ class PassiveEnvChecker(gym.Wrapper, gym.utils.RecordConstructorArgs):
 
     def reset(self, **kwargs):
         """Resets the environment that on the first call will run the `passive_env_reset_check`."""
-        if self.checked_reset is False:
+        if not self.checked_reset:
             self.checked_reset = True
             return env_reset_passive_checker(self.env, **kwargs)
         else:
@@ -58,7 +60,7 @@ class PassiveEnvChecker(gym.Wrapper, gym.utils.RecordConstructorArgs):
 
     def render(self, *args, **kwargs):
         """Renders the environment that on the first call will run the `passive_env_render_check`."""
-        if self.checked_render is False:
+        if not self.checked_render:
             self.checked_render = True
             return env_render_passive_checker(self.env, *args, **kwargs)
         else:
@@ -77,3 +79,17 @@ class PassiveEnvChecker(gym.Wrapper, gym.utils.RecordConstructorArgs):
 
         self._cached_spec = env_spec
         return env_spec
+
+    def close(self):
+        """Warns if calling close on a closed environment fails."""
+        if not self.close_called:
+            self.close_called = True
+            return self.env.close()
+        else:
+            try:
+                return self.env.close()
+            except Exception as e:
+                logger.warn(
+                    "Calling `env.close()` on the closed environment should be allowed, but it raised the following exception."
+                )
+                raise e

tests/testing_env.py

@@ -58,7 +58,7 @@ class GenericTestEnv(gym.Env):
         metadata: dict[str, Any] = {"render_modes": []},
         render_mode: str | None = None,
         spec: EnvSpec = EnvSpec(
-            "TestingEnv-v0", "testing-env-no-entry-point", max_episode_steps=100
+            "TestingEnv-v0", "tests.testing_env:GenericTestEnv", max_episode_steps=100
         ),
     ):
         """Generic testing environment constructor.