[Material Graph]Fix up texture node serialization.

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Testing/IntegrationTests/Graphs/WithSubGraph.ShaderGraph

         JSONnodeData: "{\n    \"m_GuidSerialized\": \"f4d20b5e-052c-48dd-8232-e0a67d391307\",\n
           \   \"m_Name\": \"Texture\",\n    \"m_DrawData\": {\n        \"m_Expanded\":
           false,\n        \"m_Position\": {\n            \"serializedVersion\": \"2\",\n
-          \           \"x\": -30.83177947998047,\n            \"y\": -514.542236328125,\n
-          \           \"width\": -1367.957763671875,\n            \"height\": 568.8974609375\n
+          \           \"x\": -49.50739288330078,\n            \"y\": -533.2178344726563,\n
+          \           \"width\": -1349.2821044921875,\n            \"height\": 587.5730590820313\n
           \       }\n    },\n    \"m_SerializableSlots\": [\n        {\n            \"typeInfo\":
           {\n                \"fullName\": \"UnityEngine.MaterialGraph.MaterialSlot\",\n
           \               \"assemblyName\": \"Assembly-CSharp\"\n            },\n
           \   },\\n    \\\"m_ConcreteValueType\\\": 2,\\n    \\\"m_ShaderOutputName\\\":
           \\\"UV\\\"\\n}\"\n        }\n    ],\n    \"m_OutputPrecision\": 1,\n    \"m_PropertyName\":
           \"\",\n    \"m_Description\": \"\",\n    \"m_Exposed\": 1,\n    \"m_TextureGuid\":
-          \"28bdf1ba8c076ef4e910b59cc1baf342\",\n    \"m_TextureType\": 0\n}"
+          \"76c3d794167d8524481195736f067518\",\n    \"m_TextureType\": 0\n}"
       - typeInfo:
           fullName: UnityEngine.MaterialGraph.Vector1Node
           assemblyName: Assembly-CSharp

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Testing/IntegrationTests/PropertyNodeTests.cs

 using System;
 using System.Collections.Generic;
+using System.IO;
+using System.Linq;
 using NUnit.Framework;
 using UnityEngine;
 using UnityEngine.Graphing;
             Debug.logger.logHandler = new ConsoleLogHandler();
         }
 
+        private static readonly string[] s_TexturePath =
+        {
+            "Assets",
+            "UnityShaderEditor",
+            "Editor",
+            "Testing",
+            "IntegrationTests",
+            "Textures",
+            "MudDiffuse.tif"
+
+        };
+
+        private static Texture2D FindTestTexture()
+        {
+            var texturePath = s_TexturePath.Aggregate(Path.Combine);
+            return AssetDatabase.LoadAssetAtPath<Texture2D>(texturePath);
+        }
+
         [SetUp]
         public void TestSetUp()
         {
         [Test]
         public void TestTextureNodeReturnsCorrectValue()
         {
-            m_TextureNode.defaultTexture = null;
-            Assert.AreEqual(null, m_TextureNode.defaultTexture);
+            m_TextureNode.defaultTexture = FindTestTexture();
+            Assert.AreEqual(FindTestTexture(), m_TextureNode.defaultTexture);
 
             m_TextureNode.textureType = TextureType.Bump;
             Assert.AreEqual(TextureType.Bump, m_TextureNode.textureType);
         public void TestTextureNodeReturnsPreviewProperty()
         {
             var props = new List<PreviewProperty>();
-            m_TextureNode.defaultTexture = null;
+            m_TextureNode.defaultTexture = FindTestTexture();
-            Assert.AreEqual(props.Count, 1);
+            Assert.AreEqual(1, props.Count);
-            Assert.AreEqual(null, m_TextureNode.defaultTexture);
+            Assert.AreEqual(FindTestTexture(), m_TextureNode.defaultTexture);
         }
 
         [Test]
             m_TextureNode.exposedState = PropertyNode.ExposedState.NotExposed;
             var generator = new PropertyGenerator();
             m_TextureNode.GeneratePropertyBlock(generator, GenerationMode.SurfaceShader);
-            Assert.AreEqual(string.Empty, generator.GetShaderString(0));
-            var expected = m_TextureNode.propertyName
+            var expected1 = "[NonModifiableTextureData] "
+                           + m_TextureNode.propertyName
-                           + "\", Texture) = ("
-
-                           + ")"
+                           + "\", 2D) = \"bump\" {}"
-
+            Assert.AreEqual(expected1, generator.GetShaderString(0));
+            
+            var expected2 = m_TextureNode.propertyName
+                           + "(\""
+                           + m_TextureNode.description
+                           + "\", 2D) = \"bump\" {}"
+                           + Environment.NewLine;
+            generator = new PropertyGenerator();
-            Assert.AreEqual(expected, generator.GetShaderString(0));
+            Assert.AreEqual(expected2, generator.GetShaderString(0));
         }
 
         [Test]
             m_TextureNode.exposedState = PropertyNode.ExposedState.NotExposed;
             var generator = new ShaderGenerator();
             m_TextureNode.GeneratePropertyUsages(generator, GenerationMode.SurfaceShader);
-            Assert.AreEqual(string.Empty, generator.GetShaderString(0));
-
-            var expected = m_TextureNode.precision
-                           + "4 "
-                           + m_TextureNode.propertyName
-                           + ";"
-                           + Environment.NewLine;
-
+            var expected = "sampler2D "
+                          + m_TextureNode.propertyName
+                          + ";"
+                          + Environment.NewLine;
+            Assert.AreEqual(expected, generator.GetShaderString(0));
+           
+            generator = new ShaderGenerator();
             m_TextureNode.GeneratePropertyUsages(generator, GenerationMode.SurfaceShader);
             Assert.AreEqual(expected, generator.GetShaderString(0));
         }

MaterialGraphProject/Assets/UnityShaderEditor/Runtime/Nodes/TextureNode.cs

+using System;
+using System.Collections.Generic;
 using System.Linq;
 #if UNITY_EDITOR
 using UnityEditor;
         public const int OutputSlotAId = 5;
 
         [SerializeField]
-        private string m_TextureGuid;
+        private string m_SerializedTexture;
+        [Serializable]
+        private class TextureHelper
+        {
+            public Texture2D texture;
+        }
+        
         public override bool hasPreview { get { return true; } }
 
 #if UNITY_EDITOR
             {
-                if (string.IsNullOrEmpty(m_TextureGuid))
+                if (string.IsNullOrEmpty(m_SerializedTexture))
-                var path = AssetDatabase.GUIDToAssetPath(m_TextureGuid);
-                if (string.IsNullOrEmpty(path))
-                    return null;
-
-                return AssetDatabase.LoadAssetAtPath<Texture2D>(path);
+                var tex = new TextureHelper();
+                EditorJsonUtility.FromJsonOverwrite(m_SerializedTexture, tex);
+                return tex.texture;
-                var assetPath = AssetDatabase.GetAssetPath(value);
-                if (string.IsNullOrEmpty(assetPath))
-                    return;
-
-                m_TextureGuid = AssetDatabase.AssetPathToGUID(assetPath);
+                var tex = new TextureHelper();
+                tex.texture = value;
+                m_SerializedTexture = EditorJsonUtility.ToJson(tex, true);
-        public Texture2D defaultTexture
-        {
-            get
-            {
-                return Texture2D.whiteTexture;
-            }
-            set
-            {}
-        }
+        public Texture2D defaultTexture {get;set;}
 #endif
 
         public TextureType textureType
                     break;
             }
             return GetVariableNameForNode() + slotOutput;
+        }
+
+        public override void CollectPreviewMaterialProperties(List<PreviewProperty> properties)
+        {
+            properties.Add(GetPreviewProperty());
         }
 
         public void GenerateVertexToFragmentBlock(ShaderGenerator visitor, GenerationMode generationMode)