From 714c367b9d4b7d220ef6f427882f8cdec0d3348b Mon Sep 17 00:00:00 2001
From: Raoul Khouri <69156393+raoul-khour-ts@users.noreply.github.com>
Date: Tue, 2 Feb 2021 07:11:57 -0500
Subject: [PATCH] [RLlib] Trainer._validate_config idempotentcy correction
 (issue 13427) (#13556)

---
 rllib/BUILD                 |  7 +++++++
 rllib/agents/trainer.py     |  2 +-
 rllib/tests/test_trainer.py | 30 ++++++++++++++++++++++++++++++
 3 files changed, 38 insertions(+), 1 deletion(-)
 create mode 100644 rllib/tests/test_trainer.py

diff --git a/rllib/BUILD b/rllib/BUILD
index dd1d4c163..9658983ab 100644
--- a/rllib/BUILD
+++ b/rllib/BUILD
@@ -1509,6 +1509,13 @@ py_test(
     srcs = ["tests/test_timesteps.py"]
 )
 
+py_test(
+    name = "tests/test_trainer",
+    tags = ["tests_dir", "tests_dir_T"],
+    size = "small",
+    srcs = ["tests/test_trainer.py"]
+)
+
 # --------------------------------------------------------------------
 # examples/ directory
 #
diff --git a/rllib/agents/trainer.py b/rllib/agents/trainer.py
index 47e637f6d..65e315a1d 100644
--- a/rllib/agents/trainer.py
+++ b/rllib/agents/trainer.py
@@ -1094,7 +1094,7 @@ class Trainer(Trainable):
             if model_config.get("_time_major"):
                 raise ValueError("`model._time_major` only supported "
                                  "iff `_use_trajectory_view_api` is True!")
-            elif traj_view_framestacks != "auto":
+            elif traj_view_framestacks not in ["auto", 0]:
                 raise ValueError("`model.num_framestacks` only supported "
                                  "iff `_use_trajectory_view_api` is True!")
             model_config["num_framestacks"] = 0
diff --git a/rllib/tests/test_trainer.py b/rllib/tests/test_trainer.py
new file mode 100644
index 000000000..7555c27c5
--- /dev/null
+++ b/rllib/tests/test_trainer.py
@@ -0,0 +1,30 @@
+"""Testing for trainer class"""
+import copy
+import unittest
+from ray.rllib.agents.trainer import Trainer, COMMON_CONFIG
+
+
+class TestTrainer(unittest.TestCase):
+    def test_validate_config_idempotent(self):
+        """
+        Asserts that validate_config run multiple
+        times on COMMON_CONFIG will be idempotent
+        """
+        # Given
+        standard_config = copy.deepcopy(COMMON_CONFIG)
+        standard_config["_use_trajectory_view_api"] = False
+
+        # When (we validate config 2 times)
+        Trainer._validate_config(standard_config)
+        config_v1 = copy.deepcopy(standard_config)
+        Trainer._validate_config(standard_config)
+        config_v2 = copy.deepcopy(standard_config)
+
+        # Then
+        self.assertEqual(config_v1, config_v2)
+
+
+if __name__ == "__main__":
+    import pytest
+    import sys
+    sys.exit(pytest.main(["-v", __file__]))