FIX: Avoid making new created assets dirty when opened (#1761)

* Avoid new created assets to be dirty when opened

* Add methods to check asset for default json layout and being empty

* Improve dirty asset detection when new asset is first created

Ideally at this stage, the file on disk should have a serializable equivalent as the serialized asset. However, because the new asset on disk is being created with a specific default json layout, the serialized JSON asset doesn't have not the same content.
There are opportunities for change in this area.

* Remove default json layout check method

* Update renamed constant

Author: jfreire-unity

Packages/com.unity.inputsystem/InputSystem/Actions/InputActionAsset.cs

@@ -83,6 +83,8 @@ public class InputActionAsset : ScriptableObject, IInputActionCollection2
         /// InputActionAssets.
         /// </remarks>
         public const string Extension = "inputactions";
+        ////REVIEW: actually pre-populate with some stuff?
+        internal const string kDefaultAssetLayoutJson = "{}";
 
         /// <summary>
         /// True if any action in the asset is currently enabled.
@@ -872,6 +874,11 @@ internal void MarkAsDirty()
 #endif
         }
 
+        internal bool IsEmpty()
+        {
+            return actionMaps.Count == 0 && controlSchemes.Count == 0;
+        }
+
         internal void OnWantToChangeSetup()
         {
             if (m_ActionMaps.LengthSafe() > 0)

Packages/com.unity.inputsystem/InputSystem/Editor/AssetImporter/InputActionImporter.cs

@@ -212,15 +212,12 @@ public override void OnImportAsset(AssetImportContext ctx)
             InputActionEditorWindow.RefreshAllOnAssetReimport();
         }
 
-        ////REVIEW: actually pre-populate with some stuff?
-        private const string kDefaultAssetLayout = "{}";
-
         // Add item to plop an .inputactions asset into the project.
         [MenuItem("Assets/Create/Input Actions")]
         public static void CreateInputAsset()
         {
             ProjectWindowUtil.CreateAssetWithContent("New Controls." + InputActionAsset.Extension,
-                kDefaultAssetLayout, (Texture2D)EditorGUIUtility.Load(kAssetIcon));
+                InputActionAsset.kDefaultAssetLayoutJson, (Texture2D)EditorGUIUtility.Load(kAssetIcon));
         }
     }
 }

Packages/com.unity.inputsystem/InputSystem/Editor/UITKAssetEditor/InputActionsEditorWindow.cs

@@ -223,6 +223,14 @@ private void DirtyInputActionsEditorWindow(InputActionsEditorState newState)
         private bool HasAssetChanged(SerializedObject serializedAsset)
         {
             var asset = (InputActionAsset)serializedAsset.targetObject;
+
+            // Checks if the asset being edited is a new asset that was never saved before.
+            // If it is, there's nothing to save.
+            // At the moment, an asset only has the default asset layout content on disk when it is first created.
+            // So in this case we cannot go through the normal path and compare what's on disk with what has been serialized.
+            if (m_AssetJson == InputActionAsset.kDefaultAssetLayoutJson && asset.IsEmpty())
+                return false;
+
             var newAssetJson = asset.ToJson();
             return newAssetJson != m_AssetJson;
         }