add debugging option to ModelOverrider, handle scene resets (#3997)

Project/Assets/ML-Agents/Examples/SharedAssets/Scripts/ModelOverrider.cs

 using System.IO;
 using Unity.MLAgents;
 using Unity.MLAgents.Policies;
+#if UNITY_EDITOR
+using UnityEditor;
+#endif
 
 namespace Unity.MLAgentsExamples
 {
         int m_MaxEpisodes;
 
         int m_NumSteps;
+        int m_PreviousNumSteps;
+        int m_PreviousAgentCompletedEpisodes;
+        [Tooltip("Debug values to be used in place of the command line for overriding models.")]
+        public string debugCommandLineOverride;
+
+        // Static values to keep track of completed episodes and steps across resets
+        // These are updated in OnDisable.
+        static int s_PreviousAgentCompletedEpisodes;
+        static int s_PreviousNumSteps;
+
+        int TotalCompletedEpisodes
+        {
+            get { return m_PreviousAgentCompletedEpisodes + (m_Agent == null ? 0 : m_Agent.CompletedEpisodes);  }
+        }
+
+        int TotalNumSteps
+        {
+            get { return m_PreviousNumSteps + m_NumSteps; }
+        }
 
         /// <summary>
         /// Get the asset path to use from the commandline arguments.
             m_BehaviorNameOverrides.Clear();
 
             var maxEpisodes = 0;
+            string[] commandLineArgsOverride = null;
+            if (!string.IsNullOrEmpty(debugCommandLineOverride) && Application.isEditor)
+            {
+                commandLineArgsOverride = debugCommandLineOverride.Split(' ');
+            }
-            var args = Environment.GetCommandLineArgs();
+            var args = commandLineArgsOverride ?? Environment.GetCommandLineArgs();
             for (var i = 0; i < args.Length; i++)
             {
                 if (args[i] == k_CommandLineModelOverrideFlag && i < args.Length-2)
 
         void OnEnable()
         {
+            // Start with these initialized to previous values in the case where we're resetting scenes.
+            m_PreviousNumSteps = s_PreviousNumSteps;
+            m_PreviousAgentCompletedEpisodes = s_PreviousAgentCompletedEpisodes;
+
             m_Agent = GetComponent<Agent>();
 
             GetAssetPathFromCommandLine();
             }
         }
 
+        void OnDisable()
+        {
+            // Update the static episode and step counts.
+            // For a single agent in the scene, this will be a straightforward increment.
+            // If there are multiple agents, we'll increment the count by the Agent that completed the most episodes.
+            s_PreviousAgentCompletedEpisodes = Mathf.Max(s_PreviousAgentCompletedEpisodes, TotalCompletedEpisodes);
+            s_PreviousNumSteps = Mathf.Max(s_PreviousNumSteps, TotalNumSteps);
+        }
+
         void FixedUpdate()
         {
             if (m_MaxEpisodes > 0)
                 // Since we exit as soon as *any* Agent hits its target, the maxSteps condition keeps us running
                 // a bit longer in case there's an early failure.
-                if (m_Agent.CompletedEpisodes >= m_MaxEpisodes && m_NumSteps > m_MaxEpisodes * m_Agent.MaxStep)
+                if (TotalCompletedEpisodes >= m_MaxEpisodes && TotalNumSteps > m_MaxEpisodes * m_Agent.MaxStep)
+                    Debug.Log($"ModelOverride reached {TotalCompletedEpisodes} episodes and {TotalNumSteps} steps. Exiting.");
+#if UNITY_EDITOR
+                    EditorApplication.isPlaying = false;
+#endif
                 }
             }
             m_NumSteps++;