Add debug agent for limiting game length.

kaggle_environments/envs/open_spiel/open_spiel.py

@@ -421,8 +421,32 @@ def random_agent(
   return {"submission": int(action)}
 
 
+def debug_agent(
+  observation: dict[str, Any],
+  configuration: dict[str, Any],
+  max_history_length: int = 8,
+) -> int:
+  """A built-in random agent specifically for OpenSpiel environments."""
+  del configuration
+  serialized_game_and_state = observation.get("serializedGameAndState")
+  if not serialized_game_and_state:
+    return None
+  game, state = pyspiel.deserialize_game_and_state(serialized_game_and_state)
+  if len(state.history()) >= max_history_length:
+    return {
+      "submission": pyspiel.INVALID_ACTION,
+      "status": "Max history length reached; intentionally submitting invalid action.",
+    }
+  legal_actions = observation.get("legalActions")
+  if not legal_actions:
+    return None
+  action = random.choice(legal_actions)
+  return {"submission": int(action)}
+
+
 AGENT_REGISTRY = {
   "random": random_agent,
+  "debug": debug_agent,
 }
 
 

kaggle_environments/envs/open_spiel/test_open_spiel.py

@@ -1,5 +1,7 @@
-from absl.testing import absltest
+import functools
 import sys
+
+from absl.testing import absltest
 from kaggle_environments import make
 import pyspiel
 from . import open_spiel as open_spiel_env
@@ -91,6 +93,22 @@ def test_agent_error(self):
     self.assertEqual(json["rewards"], [None, None])
     self.assertEqual(json["statuses"], ["ERROR", "ERROR"])
 
+  def test_debug_agent(self):
+    env = make("open_spiel_chess", debug=True)
+    max_history_length = 5
+    debug_agent = functools.partial(
+      open_spiel_env.debug_agent,
+      max_history_length=max_history_length,
+    )
+    env.run([debug_agent, "random"])
+    json = env.toJSON()
+    self.assertEqual(json["rewards"], [-1, 1])
+    self.assertEqual(json["statuses"], ["DONE", "DONE"])
+    self.assertEqual(
+      len(json["info"]["actionHistory"]),
+      max_history_length,
+    )
+
 
 if __name__ == '__main__':
   absltest.main()