[Feature] Custom conversion tool for gym specs

ghstack-source-id: 7b99a47cd9091cdf8cad6d84f3ede73a010b8be9
Pull Request resolved: #2726

docs/source/reference/envs.rst

@@ -1117,7 +1117,7 @@ in the relevant functions:
     >>> print(env2._env.env.env)
     <gym.envs.classic_control.pendulum.PendulumEnv at 0x1629916a0>
 
-We can see that the two libraries modify the value returned by :func:`~.gym.gym_backend()`
+We can see that the two libraries modify the value returned by :func:`~torchrl.envs.gym.gym_backend()`
 which can be further used to indicate which library needs to be used for
 the current computation. :class:`~.gym.set_gym_backend` is also a decorator:
 we can use it to tell to a specific function what gym backend needs to be used
@@ -1188,3 +1188,4 @@ the following function will return ``1`` when queried:
     VmasWrapper
     gym_backend
     set_gym_backend
+    register_gym_spec_conversion

test/test_libs.py

@@ -79,6 +79,7 @@
     Composite,
     MultiCategorical,
     MultiOneHot,
+    NonTensor,
     OneHot,
     ReplayBuffer,
     ReplayBufferEnsemble,
@@ -119,6 +120,7 @@
     GymWrapper,
     MOGymEnv,
     MOGymWrapper,
+    register_gym_spec_conversion,
     set_gym_backend,
 )
 from torchrl.envs.libs.habitat import _has_habitat, HabitatEnv
@@ -337,6 +339,39 @@ def test_gym_spec_cast(self, categorical):
         assert spec == recon
         assert recon.shape == spec.shape
 
+    def test_gym_new_spec_reg(self):
+        Space = gym_backend("spaces").Space
+
+        class MySpaceParent(Space):
+            ...
+
+        s_parent = MySpaceParent()
+
+        class MySpaceChild(MySpaceParent):
+            ...
+
+        # We intentionally register first the child then the parent
+        @register_gym_spec_conversion(MySpaceChild)
+        def convert_myspace_child(spec, **kwargs):
+            return NonTensor((), example_data="child")
+
+        @register_gym_spec_conversion(MySpaceParent)
+        def convert_myspace_parent(spec, **kwargs):
+            return NonTensor((), example_data="parent")
+
+        s_child = MySpaceChild()
+        assert _gym_to_torchrl_spec_transform(s_parent).example_data == "parent"
+        assert _gym_to_torchrl_spec_transform(s_child).example_data == "child"
+
+        class NoConversionSpace(Space):
+            ...
+
+        s_no_conv = NoConversionSpace()
+        with pytest.raises(
+            KeyError, match="No conversion tool could be found with the gym space"
+        ):
+            _gym_to_torchrl_spec_transform(s_no_conv)
+
     @pytest.mark.parametrize("order", ["tuple_seq"])
     @implement_for("gym")
     def test_gym_spec_cast_tuple_sequential(self, order):

torchrl/envs/__init__.py

@@ -32,6 +32,7 @@
     OpenSpielWrapper,
     PettingZooEnv,
     PettingZooWrapper,
+    register_gym_spec_conversion,
     RoboHiveEnv,
     set_gym_backend,
     SMACv2Env,

torchrl/envs/libs/__init__.py

@@ -12,6 +12,7 @@
     GymWrapper,
     MOGymEnv,
     MOGymWrapper,
+    register_gym_spec_conversion,
     set_gym_backend,
 )
 from .habitat import HabitatEnv