feat: use protocol to force all environment states to have a key (#45)

Co-authored-by: Clément Bonnet <56230714+clement-bonnet@users.noreply.github.com>

jumanji/env.py

@@ -15,14 +15,21 @@
 """Abstract environment class"""
 
 import abc
-from typing import Any, Generic, Tuple, TypeVar
+from typing import Any, Generic, Protocol, Tuple, TypeVar
 
-from chex import PRNGKey
+import chex
 
 from jumanji import specs
 from jumanji.types import Action, TimeStep
 
-State = TypeVar("State")
+
+class StateProtocol(Protocol):
+    """Enforce that the State for every Environment must implement a key."""
+
+    key: chex.PRNGKey
+
+
+State = TypeVar("State", bound="StateProtocol")
 
 
 class Environment(abc.ABC, Generic[State]):
@@ -36,7 +43,7 @@ def __repr__(self) -> str:
         return "Environment."
 
     @abc.abstractmethod
-    def reset(self, key: PRNGKey) -> Tuple[State, TimeStep]:
+    def reset(self, key: chex.PRNGKey) -> Tuple[State, TimeStep]:
         """Resets the environment to an initial state.
 
         Args:

jumanji/environments/combinatorial/cvrp/types.py

@@ -14,11 +14,14 @@
 
 from typing import TYPE_CHECKING, NamedTuple
 
+import jax.random
+
 if TYPE_CHECKING:  # https://github.com/python/mypy/issues/6239
     from dataclasses import dataclass
 else:
     from chex import dataclass
 
+import chex
 import jax.numpy as jnp
 from chex import Array
 
@@ -42,6 +45,7 @@ class State:
     visited_mask: Array  # (problem_size + 1,)
     order: Array  # (2 * problem_size,) - this size is worst-case (visit depot after each node)
     num_total_visits: jnp.int32
+    key: chex.PRNGKey = jax.random.PRNGKey(0)
 
 
 class Observation(NamedTuple):

jumanji/environments/combinatorial/knapsack/types.py

@@ -14,6 +14,9 @@
 
 from typing import TYPE_CHECKING, NamedTuple
 
+import chex
+import jax.random
+
 if TYPE_CHECKING:  # https://github.com/python/mypy/issues/6239
     from dataclasses import dataclass
 else:
@@ -40,6 +43,7 @@ class State:
     used_mask: Array  # (problem_size,)
     num_steps: jnp.int32
     remaining_budget: jnp.float32
+    key: chex.PRNGKey = jax.random.PRNGKey(0)
 
 
 class Observation(NamedTuple):

jumanji/environments/combinatorial/tsp/types.py

@@ -14,6 +14,9 @@
 
 from typing import TYPE_CHECKING, NamedTuple
 
+import chex
+import jax.random
+
 if TYPE_CHECKING:  # https://github.com/python/mypy/issues/6239
     from dataclasses import dataclass
 else:
@@ -38,6 +41,7 @@ class State:
     visited_mask: Array  # (problem_size,)
     order: Array  # (problem_size,)
     num_visited: jnp.int32
+    key: chex.PRNGKey = jax.random.PRNGKey(0)
 
 
 class Observation(NamedTuple):

jumanji/environments/games/connect4/types.py

@@ -14,7 +14,9 @@
 
 from typing import TYPE_CHECKING
 
+import chex
 import jax.numpy as jnp
+import jax.random
 from chex import Array
 from typing_extensions import TypeAlias
 
@@ -30,6 +32,7 @@
 class State:
     current_player: jnp.int8
     board: Board
+    key: chex.PRNGKey = jax.random.PRNGKey(0)
 
 
 @dataclass

jumanji/wrappers.py

@@ -35,10 +35,9 @@
 from jax import jit, random
 
 from jumanji import specs, tree_utils
-from jumanji.env import Environment
+from jumanji.env import Environment, State
 from jumanji.types import Action, TimeStep, restart, termination, transition
 
-State = TypeVar("State")
 Observation = TypeVar("Observation")
 
 # Type alias that corresponds to ObsType in the Gym API