[VFX] Fix Error Feedback with CustomHLSL

Fix wrong error feedback with relative path, add a missing check using base path.
Issue technically introduced at https://github.cds.internal.unity3d.com/unity/unity/commit/de946b09b4e9e9f3e06853c8f5465f5403f5ec96 but this isn't a regression since it's a new error feedback.

Author: PaulDemeulenaere

Packages/com.unity.visualeffectgraph/Editor/Models/Blocks/Implementations/HLSL/CustomHLSL.cs

@@ -243,7 +243,9 @@ internal override void GenerateErrors(VFXErrorReporter report)
             base.GenerateErrors(report);
             var hlslValidator = new CustomHLSLBlockFunctionValidator();
             ParseCodeIfNeeded();
-            foreach(var error in hlslValidator.Validate(m_AvailableFunction.values, m_Function, includes))
+
+            var basePath = Path.GetDirectoryName(AssetDatabase.GetAssetPath(GetGraph().GetResource()));
+            foreach(var error in hlslValidator.Validate(m_AvailableFunction.values, m_Function, basePath, includes))
             {
                 report.RegisterError(string.Empty, error.type, error.message, this);
             }

Packages/com.unity.visualeffectgraph/Editor/Models/Operators/Implementations/CustomHLSL.cs

@@ -11,7 +11,7 @@ namespace UnityEditor.VFX.Operator
 {
     abstract class CustomHLSLFunctionValidator
     {
-        public IEnumerable<IHLSMessage> Validate(IEnumerable<string> functions, HLSLFunction selectedFunction, IEnumerable<string> includes)
+        public IEnumerable<IHLSMessage> Validate(IEnumerable<string> functions, HLSLFunction selectedFunction, string basePath, IEnumerable<string> includes)
         {
             if (functions == null || selectedFunction == null)
             {
@@ -63,7 +63,10 @@ public IEnumerable<IHLSMessage> Validate(IEnumerable<string> functions, HLSLFunc
                 var guid = AssetDatabase.AssetPathToGUID(include);
                 if (string.IsNullOrEmpty(guid))
                 {
-                    yield return new HLSLMissingIncludeFile(include);
+                    //Try with Relative Path
+                    guid = AssetDatabase.AssetPathToGUID(Path.Combine(basePath, include));
+                    if (string.IsNullOrEmpty(guid))
+                        yield return new HLSLMissingIncludeFile(include);
                 }
             }
 
@@ -270,7 +273,9 @@ internal override void GenerateErrors(VFXErrorReporter report)
             base.GenerateErrors(report);
             var hlslValidator = new CustomHLSLOperatorFunctionValidator();
             ParseCodeIfNeeded();
-            foreach(var error in hlslValidator.Validate(m_AvailableFunctions.values, m_Function, includes))
+
+            var basePath = Path.GetDirectoryName(AssetDatabase.GetAssetPath(GetGraph().GetResource()));
+            foreach (var error in hlslValidator.Validate(m_AvailableFunctions.values, m_Function, basePath, includes))
             {
                 report.RegisterError(string.Empty, error.type, error.message, this);
             }

Tests/SRPTests/Projects/VisualEffectGraph_HDRP/Assets/AllTests/Editor/Tests/CustomHLSLOperatorTest.cs

@@ -1,6 +1,7 @@
 #if !UNITY_EDITOR_OSX || MAC_FORCE_TESTS
 using System;
 using System.Collections;
+using System.IO;
 using System.Linq;
 using System.Reflection;
 
@@ -180,6 +181,33 @@ public IEnumerator Check_CustomHLSL_Operator_No_Function()
             Assert.AreEqual("No valid HLSL function has been provided. You should write at least one function that returns a value", report.description);
         }
 
+        [UnityTest]
+        public IEnumerator Check_CustomHLSL_Operator_IncludePath_Relative_Path_Success()
+        {
+            // Arrange
+            var hlslOperator = ScriptableObject.CreateInstance<CustomHLSL>();
+            CustomHLSLBlockTest.CreateShaderFile(defaultHlslCode, out var shaderIncludePath);
+            shaderIncludePath = Path.GetFileName(shaderIncludePath);
+
+            var hlslCode = string.Format("#include \"{0}\"", shaderIncludePath);
+            hlslCode += @"
+float3 Transform(float3 a, float3 b)
+{
+    return a + b;
+}";
+            hlslOperator.SetSettingValue("m_HLSLCode", hlslCode);
+            MakeSimpleGraphWithCustomHLSL(hlslOperator, out var view, out var graph);
+
+            yield return null;
+
+            // Act
+            graph.errorManager.GenerateErrors();
+
+            // Assert
+            var report = graph.errorManager.errorReporter.GetDirtyModelErrors(hlslOperator);
+            Assert.IsTrue(!report.Any());
+        }
+
         [UnityTest]
         public IEnumerator Check_CustomHLSL_Operator_IncludePath_Fail()
         {