CHANGED TO MIRROR

Assets/Mirror/Editor/Weaver/EntryPoint/EnterPlayModeHook.cs

@@ -0,0 +1,44 @@
+#if !UNITY_2020_3_OR_NEWER
+// make sure we weaved successfully when entering play mode.
+using UnityEditor;
+using UnityEngine;
+
+namespace Mirror
+{
+    public class EnterPlayModeSettingsCheck : MonoBehaviour
+    {
+        [InitializeOnLoadMethod]
+        static void OnInitializeOnLoad()
+        {
+            // Hook this event to see if we have a good weave every time
+            // user attempts to enter play mode or tries to do a build
+            EditorApplication.playModeStateChanged += OnPlayModeStateChanged;
+        }
+
+        static void OnPlayModeStateChanged(PlayModeStateChange state)
+        {
+            // Per Unity docs, this fires "when exiting edit mode before the Editor is in play mode".
+            // This doesn't fire when closing the editor.
+            if (state == PlayModeStateChange.ExitingEditMode)
+            {
+                // Check if last weave result was successful
+                if (!SessionState.GetBool("MIRROR_WEAVE_SUCCESS", false))
+                {
+                    // Last weave result was a failure...try to weave again
+                    // Faults will show in the console that may have been cleared by "Clear on Play"
+                    SessionState.SetBool("MIRROR_WEAVE_SUCCESS", true);
+                    Weaver.CompilationFinishedHook.WeaveExistingAssemblies();
+
+                    // Did that clear things up for us?
+                    if (!SessionState.GetBool("MIRROR_WEAVE_SUCCESS", false))
+                    {
+                        // Nope, still failed, and console has the issues logged
+                        Debug.LogError("Can't enter play mode until weaver issues are resolved.");
+                        EditorApplication.isPlaying = false;
+                    }
+                }
+            }
+        }
+    }
+}
+#endif