fix: MirrorNetworking#3144 Reader/Writer Sprite null support & test t…

…o guarantee it never happens again

Assets/Mirror/Runtime/NetworkReaderExtensions.cs

@@ -292,7 +292,13 @@ public static Texture2D ReadTexture2D(this NetworkReader reader)
 
         public static Sprite ReadSprite(this NetworkReader reader)
         {
-            return Sprite.Create(reader.ReadTexture2D(), reader.ReadRect(), reader.ReadVector2());
+            // support 'null' textures for [SyncVar]s etc.
+            // https://github.com/vis2k/Mirror/issues/3144
+            Texture2D texture = reader.ReadTexture2D();
+            if (texture == null) return null;
+
+            // otherwise create a valid sprite
+            return Sprite.Create(texture, reader.ReadRect(), reader.ReadVector2());
         }
     }
 }

Assets/Mirror/Runtime/NetworkWriterExtensions.cs

@@ -312,6 +312,15 @@ public static void WriteTexture2D(this NetworkWriter writer, Texture2D texture2D
 
         public static void WriteSprite(this NetworkWriter writer, Sprite sprite)
         {
+            // support 'null' textures for [SyncVar]s etc.
+            // https://github.com/vis2k/Mirror/issues/3144
+            // simply send a 'null' for texture content.
+            if (sprite == null)
+            {
+                writer.WriteTexture2D(null);
+                return;
+            }
+
             writer.WriteTexture2D(sprite.texture);
             writer.WriteRect(sprite.rect);
             writer.WriteVector2(sprite.pivot);

Assets/Mirror/Tests/Editor/NetworkWriterTest.cs

@@ -1520,5 +1520,19 @@ public void WriteSprite_normal()
             Assert.That(sprite.texture.height, Is.EqualTo(example.texture.height));
             Assert.That(sprite.texture.GetPixels32().SequenceEqual(example.texture.GetPixels32()));
         }
+
+        // test to prevent https://github.com/vis2k/Mirror/issues/3144
+        [Test]
+        public void WriteSprite_Null()
+        {
+            // write
+            NetworkWriter writer = new NetworkWriter();
+            writer.WriteSprite(null);
+
+            // read
+            NetworkReader reader = new NetworkReader(writer.ToArray());
+            Sprite sprite = reader.ReadSprite();
+            Assert.That(sprite, Is.Null);
+        }
     }
 }