First version of a material upgrader system (With upgrade for EmissiveColor)

com.unity.render-pipelines.high-definition/HDRP/Editor/Upgraders/UpgradeMenuItem.cs

 using UnityEngine.Experimental.Rendering.HDPipeline;
 using UnityEngine.SceneManagement;
 using UnityEditor.SceneManagement;
+using System.Linq;
+using System.Collections.Generic;
 
 namespace UnityEditor.Experimental.Rendering.HDPipeline
 {
             {
                 EditorUtility.ClearProgressBar();
             }
+        }
+
+        // Update EmissiveColor after we remove EmissiveIntensity from all shaders in 2018.2
+        // Now EmissiveColor is HDR and it must be update to the value new EmissiveColor = old EmissiveColor * EmissiveIntensity
+        static bool UpdateMaterial_EmissiveColor_2018_2(string path, Material mat)
+        {
+            // Find the missing property in the file and update EmissiveColor
+            string[] readText = File.ReadAllLines(path);
+
+            foreach (string line in readText)
+            {
+                if (line.Contains("_EmissiveIntensity:"))
+                {
+                    int startPos = line.IndexOf(":") + 1;
+                    string sub = line.Substring(startPos);
+                    float emissiveIntensity = float.Parse(sub);
+
+                    Color emissiveColor = Color.black;
+                    if (mat.HasProperty("_EmissiveColor"))
+                    {
+                        emissiveColor = mat.GetColor("_EmissiveColor");
+                    }
+
+                    emissiveColor *= emissiveIntensity;
+                    emissiveColor.a = 1.0f;
+                    mat.SetColor("_EmissiveColor", emissiveColor);
+                    // Also fix EmissionColor if needed (Allow to let HD handle GI, if black GI is disabled by legacy)
+                    mat.SetColor("_EmissionColor", Color.white);
+
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        static void UpdateMaterialFile_EmissiveColor_2018_2(string path)
+        {
+            string[] readText = File.ReadAllLines(path);
+
+            foreach (string line in readText)
+            {
+                if (line.Contains("_EmissiveIntensity:"))
+                {
+                    // Remove emissive intensity line
+                    string[] writeText = readText.Where(l => l != line).ToArray();
+                    File.WriteAllLines(path, writeText);
+                    return;
+                }
+            }
+
+            return;
+        }
+
+        delegate bool UpdateMaterial(string path, Material mat);
+        delegate void UpdateMaterialFile(string path);
+
+        static void UpdateMaterialToNewerVersion(string caption, UpdateMaterial updateMaterial, UpdateMaterialFile updateMaterialFile = null)
+        {
+            bool VSCEnabled = (UnityEditor.VersionControl.Provider.enabled && UnityEditor.VersionControl.Provider.isActive);
+            var matIds = AssetDatabase.FindAssets("t:Material");
+            List<string> materialFiles = new List<string>(); // Contain the list dirty files
+
+            try
+            {
+                for (int i = 0, length = matIds.Length; i < length; i++)
+                {
+                    var path = AssetDatabase.GUIDToAssetPath(matIds[i]);
+                    var mat = AssetDatabase.LoadAssetAtPath<Material>(path);
+
+                    EditorUtility.DisplayProgressBar(
+                        "Update material to new version " + caption + "...",
+                        string.Format("{0} / {1} materials updated.", i, length),
+                        i / (float)(length - 1));
+
+                    if (mat.shader.name == "HDRenderPipeline/LitTessellation" ||
+                        mat.shader.name == "HDRenderPipeline/Lit" ||
+                        mat.shader.name == "HDRenderPipeline/LayeredLit" ||
+                        mat.shader.name == "HDRenderPipeline/LayeredLitTessellation" ||
+                        mat.shader.name == "HDRenderPipeline/StackLit" ||
+                        mat.shader.name == "HDRenderPipeline/Unlit"
+                         )
+                    {
+                        // Need to be processed in order - All function here should be re-entrant (i.e after upgrade it can be recall)
+                        bool dirty = updateMaterial(path, mat);
+
+                        if (dirty)
+                        {
+                            // Checkout the file and tag it as dirty
+                            CoreUtils.CheckOutFile(VSCEnabled, mat);
+                            EditorUtility.SetDirty(mat);
+                            materialFiles.Add(path);
+                        }
+                    }
+                }
+            }
+            finally
+            {
+                EditorUtility.ClearProgressBar();
+                // Save all dirty assets
+                AssetDatabase.SaveAssets();
+            }
+
+            if (updateMaterialFile == null)
+                return;
+
+            // Now that all the asset have been modified and save, we can safely update the .mat file and remove removed property
+            try
+            {
+                for (int i = 0, length = materialFiles.Count; i < length; i++)
+                {
+                    string path = materialFiles[i];
+
+                    EditorUtility.DisplayProgressBar(
+                        "Update .mat files...",
+                        string.Format("{0} / {1} materials .mat file updated.", i, length),
+                        i / (float)(length - 1));
+
+                    // Note: The file is supposed to be checkout by the previous loop
+                    updateMaterialFile(path);
+                }
+            }
+            finally
+            {
+                EditorUtility.ClearProgressBar();
+                // No need to save in this case
+            }
+        }
+
+        [MenuItem("Edit/Render Pipeline/Update all Materials to latest version", priority = CoreUtils.editMenuPriority3)]
+        static void UpdateMaterialToNewerVersion()
+        {
+            // Add here all the material upgrade function supported in this version
+            UpdateMaterialToNewerVersion("(EmissiveColor)", UpdateMaterial_EmissiveColor_2018_2, UpdateMaterialFile_EmissiveColor_2018_2);
         }
     }
 }

com.unity.render-pipelines.high-definition/HDRP/RenderPipelineResources/DefaultHDDecalMaterial.mat

     - _Drag: 1
     - _DstBlend: 0
     - _EmissiveColorMode: 1
-    - _EmissiveIntensity: 0
     - _EnableBlendModeAccurateLighting: 1
     - _EnableBlendModePreserveSpecularLighting: 1
     - _EnableFogOnTransparent: 1

com.unity.render-pipelines.high-definition/HDRP/RenderPipelineResources/DefaultHDMaterial.mat

     - _Drag: 1
     - _DstBlend: 0
     - _EmissiveColorMode: 1
-    - _EmissiveIntensity: 0
     - _EnableBlendModeAccurateLighting: 1
     - _EnableBlendModePreserveSpecularLighting: 1
     - _EnableFogOnTransparent: 1

com.unity.render-pipelines.high-definition/HDRP/RenderPipelineResources/DefaultHDMirrorMaterial.mat

     - _Drag: 1
     - _DstBlend: 0
     - _EmissiveColorMode: 1
-    - _EmissiveIntensity: 0
     - _EnableBlendModeAccurateLighting: 1
     - _EnableBlendModePreserveSpecularLighting: 1
     - _EnableFogOnTransparent: 1

com.unity.render-pipelines.high-definition/HDRP/Editor/Decal.meta

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