Fix Reconnection Logic (#168)

## Description of Changes
*Describe what has been changed, any new features or bug fixes*

- switched our "already connected" logic to using a reference to a
`MonoBehaviour` instead of just a bool. `MonoBehaviour`s are typically
destroyed when a scene reload happens and in this case we'll want to
allow developers to spawn a new `SpacetimeDBNetworkManager` if the
previous one has been destroyed.

## API

This is *not* an API break.

 - [ ] This is an API breaking change to the SDK

*If the API is breaking, please state below what will break*

## Requires SpacetimeDB PRs
*List any PRs here that are required for this SDK change to work*

- clockworklabs/SpacetimeDB#1869

## Testsuite

SpacetimeDB branch name: master

## Testing
*Write instructions for a test that you performed for this PR*

- [x] I have added in several new tests here, one of which is a
reconnection test. Also, the reason why we couldn't have more than 1
test before this is that it was required for reconnections to be working
in order to have multiple tests running in the testsuite. Now that we
have fixed reconnections I have enabled all of the tests.

Testsuite passes


![image](https://github.com/user-attachments/assets/09ef5835-f2c7-41f1-af6b-e612ac5e0497)

---------

Co-authored-by: John Detter <[email protected]>
Co-authored-by: Mazdak Farrokhzad <[email protected]>
Co-authored-by: Jeremie Pelletier <[email protected]>
Co-authored-by: Zeke Foppa <[email protected]>

.github/workflows/unity-test.yml

@@ -7,7 +7,7 @@ on:
   pull_request:
 
 jobs:
-  test:
+  unity-testsuite:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repository

.github/workflows/unity-testsuite-bindings.yml

@@ -7,7 +7,7 @@ on:
   pull_request:
 
 jobs:
-  test:
+  check-testsuite-bindings:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repository
@@ -110,7 +110,7 @@ jobs:
 
       - name: Check for changes
         run: |
-          git diff --exit-code
+          git diff --exit-code unity-tests~/client/Assets/Scripts/autogen
         continue-on-error: true
 
       - name: Fail if there are changes

.gitignore

@@ -75,3 +75,4 @@ obj~
 # This is used for local paths to SpacetimeDB packages.
 /nuget.config
 /nuget.config.meta
+.idea/

src/SpacetimeDBClient.cs

@@ -36,7 +36,10 @@ public DbConnection Build()
             }
             conn.Connect(token, uri, nameOrAddress, compression ?? Compression.Brotli);
 #if UNITY_5_3_OR_NEWER
-            SpacetimeDBNetworkManager.ActiveConnections.Add(conn);
+            if (SpacetimeDBNetworkManager._instance != null)
+            {
+                SpacetimeDBNetworkManager._instance.AddConnection(conn);    
+            }
 #endif
             return conn;
         }
@@ -163,7 +166,13 @@ protected DbConnectionBase()
             webSocket.OnMessage += OnMessageReceived;
             webSocket.OnSendError += a => onSendError?.Invoke(a);
 #if UNITY_5_3_OR_NEWER
-            webSocket.OnClose += (e) => SpacetimeDBNetworkManager.ActiveConnections.Remove(this);
+            webSocket.OnClose += (e) =>
+            {
+                if (SpacetimeDBNetworkManager._instance != null)
+                {
+                    SpacetimeDBNetworkManager._instance.RemoveConnection(this); 
+                }  
+            };
 #endif
 
             networkMessageProcessThread = new Thread(PreProcessMessages);

src/SpacetimeDBNetworkManager.cs

@@ -6,38 +6,56 @@
 
 namespace SpacetimeDB
 {
-	// This class is only used in Unity projects.
-	// Attach this to a gameobject in your scene to use SpacetimeDB.
-	public class SpacetimeDBNetworkManager : MonoBehaviour
-	{
-		private static bool _alreadyInitialized;
+    // This class is only used in Unity projects.
+    // Attach this to a GameObject in your scene to use SpacetimeDB.
+    public class SpacetimeDBNetworkManager : MonoBehaviour
+    {
+        internal static SpacetimeDBNetworkManager? _instance;
 
-		public void Awake()
-		{
-			// Ensure that users don't create several SpacetimeDBNetworkManager instances.
-			// We're using a global (static) list of active connections and we don't want several instances to walk over it several times.
-			if (_alreadyInitialized)
-			{
-				throw new InvalidOperationException("SpacetimeDBNetworkManager is a singleton and should only be attached once.");
-			}
-			else
-			{
-				_alreadyInitialized = true;
-			}
-		}
+        public void Awake()
+        {
+            // Ensure that users don't create several SpacetimeDBNetworkManager instances.
+            // We're using a global (static) list of active connections and we don't want several instances to walk over it several times.
+            if (_instance != null)
+            {
+                throw new InvalidOperationException("SpacetimeDBNetworkManager is a singleton and should only be attached once.");
+            }
+            else
+            {
+                _instance = this;
+            }
+        }
 
-		internal static HashSet<IDbConnection> ActiveConnections = new();
+        private readonly List<IDbConnection> activeConnections = new();
 
-		private void ForEachConnection(Action<IDbConnection> action)
-		{
-			foreach (var conn in ActiveConnections)
-			{
-				action(conn);
-			}
-		}
+        public bool AddConnection(IDbConnection conn)
+        {
+            if (activeConnections.Contains(conn))
+            {
+                return false;
+            }
+            activeConnections.Add(conn);
+            return true;
 
-		private void Update() => ForEachConnection(conn => conn.FrameTick());
-		private void OnDestroy() => ForEachConnection(conn => conn.Disconnect());
-	}
+        }
+
+        public bool RemoveConnection(IDbConnection conn)
+        {
+            return activeConnections.Remove(conn);
+        }
+
+        private void ForEachConnection(Action<IDbConnection> action)
+        {
+            // It's common to call disconnect from Update, which will then modify the ActiveConnections collection,
+            // therefore we must reverse-iterate the list of connections.
+            for (var x = activeConnections.Count - 1; x >= 0; x--)
+            {
+                action(activeConnections[x]);
+            }
+        }
+
+        private void Update() => ForEachConnection(conn => conn.FrameTick());
+        private void OnDestroy() => ForEachConnection(conn => conn.Disconnect());
+    }
 }
 #endif