Fixed custom function node extension case sensitivity validation

Author: SamCYu

Packages/com.unity.shadergraph/Editor/Data/Nodes/Utility/CustomFunctionNode.cs

@@ -60,7 +60,7 @@ enum SourceFileStatus
         };
 
         // With ShaderInclude asset type, it should no longer be necessary to soft-check the extension.
-        public static string[] s_ValidExtensions = { ".hlsl", ".cginc", ".cg" };
+        public static HashSet<string> s_ValidExtensions = new HashSet<string>() { ".hlsl", ".cginc", ".cg" };
         const string k_InvalidFileType = "Source file is not a valid file type. Valid file extensions are .hlsl, .cginc, and .cg";
         const string k_MissingFile = "Source file does not exist. A valid .hlsl, .cginc, or .cg file must be referenced";
         const string k_MissingOutputSlot = "A Custom Function Node must have at least one output slot";
@@ -367,7 +367,7 @@ static bool IsValidFunction(HlslSourceType sourceType, string functionName, stri
                 if (string.IsNullOrEmpty(path))
                     path = functionSource;
 
-                string extension = Path.GetExtension(path);
+                string extension = Path.GetExtension(path).ToLower();
                 return s_ValidExtensions.Contains(extension);
             }
         }
@@ -417,7 +417,7 @@ public override void ValidateNode()
                     string path = AssetDatabase.GUIDToAssetPath(functionSource);
                     if (!string.IsNullOrEmpty(path) && AssetDatabase.LoadAssetAtPath<UnityEngine.Object>(path) != null)
                     {
-                        string extension = path.Substring(path.LastIndexOf('.'));
+                        string extension = path.Substring(path.LastIndexOf('.')).ToLower();
                         if (!s_ValidExtensions.Contains(extension))
                         {
                             fileStatus = SourceFileStatus.Invalid;