Added metadata field to VectorEnv and VectorWrapper. Implements #1005. (#1006)

docs/api/vector.md

@@ -53,6 +53,10 @@ vector/utils
 
     The ``EnvSpec`` of the environment normally set during :py:meth:`gymnasium.make_vec`
 
+.. autoattribute:: gymnasium.vector.VectorEnv.metadata
+
+    The metadata of the environment containing rendering modes, rendering fps, etc
+
 .. autoattribute:: gymnasium.vector.VectorEnv.render_mode
 
     The render mode of the environment which should follow similar specifications to `Env.render_mode`.

gymnasium/vector/vector_env.py

@@ -92,6 +92,9 @@ class VectorEnv(Generic[ObsType, ActType, ArrayType]):
         :func:`make_vec` is the equivalent function to :func:`make` for vector environments.
     """
 
+    # Set this in SOME subclasses
+    metadata: dict[str, Any] = {"render_modes": []}
+
     spec: EnvSpec | None = None
     render_mode: str | None = None
     closed: bool = False
@@ -446,6 +449,11 @@ class VectorWrapper(VectorEnv):
         """Returns the `render_mode` from the base environment."""
         return self.env.render_mode
 
+    @property
+    def metadata(self) -> dict[str, Any]:
+        """Returns the `metadata` from the base environment."""
+        return self.env.metadata
+
     @property
     def np_random(self) -> np.random.Generator:
         """Returns the environment's internal :attr:`_np_random` that if not set will initialise with a random seed.

tests/vector/test_vector_wrapper.py

@@ -54,3 +54,17 @@ def test_vector_env_wrapper_attributes():
     assert np.allclose(wrapped.env.get_attr("gravity"), env.get_attr("gravity"))
 
     env.close()
+
+
+def test_vector_env_metadata():
+    """Test if `metadata` property for VectorWrapper correctly forwards to the vector env it is wrapping."""
+    env = gym.make_vec("CartPole-v1", num_envs=3, vectorization_mode="sync")
+    wrapped = DummyVectorWrapper(
+        gym.make_vec("CartPole-v1", num_envs=3, vectorization_mode="sync")
+    )
+
+    assert env.metadata == wrapped.metadata
+    env.metadata = {"render_modes": ["rgb_array"]}
+    assert env.metadata != wrapped.metadata
+
+    env.close()