[VFX] Custom hlsl parsing issues

Jira: UUM-79389

### First issue
When this HLSL function is used, the `position` attribute is not recognized
```hlsl
void Test(inout VFXAttributes attributes, in float value, in float altSize)
{
    if (attributes.position.y >= value)
    {
        attributes.size = altSize;
    }
}
```
In this simple case it does no harm, but in more complex cases it can break the shader compilation.

### Second issue
The same function, but with a different formatting is not properly parsed, leading to function's parameters not being identified.
```hlsl
void Test(inout VFXAttributes attributes
   , in float value
   , in float altSize
)
{
    if (attributes.position.y >= value)
    {
        attributes.size = altSize;
    }
}
```

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

@@ -176,7 +176,7 @@ public HLSLMissingIncludeFile(string filePath)
     class HLSLFunctionParameter
     {
         // Match inout/in/out accessor then any whitespace then the parameter type then optionally a template type any whitespace and then the parameter name
-        static readonly Regex s_ParametersParser = new Regex(@"(?<access>(inout|in|out)\b)?\s*(?<type>\w+)(?:[<](?<template>\w+)[>])?\s*(?<parameter>\w+)(?:,\s*)?", RegexOptions.Compiled);
+        static readonly Regex s_ParametersParser = new Regex(@"(?<access>(inout|in|out)\b)?\s*(?<type>\w+)(?:[<](?<template>\w+)[>])?\s*(?<parameter>\w+)(?:\s*,\s*)?", RegexOptions.Compiled);
 
         readonly string m_RawCode;
 
@@ -200,7 +200,7 @@ public static IEnumerable<HLSLFunctionParameter> Parse(string hlsl, Dictionary<s
                     match.Groups["type"].Value,
                     match.Groups["template"].Value,
                     match.Groups["parameter"].Value,
-                    doc.TryGetValue(match.Groups["parameter"].Value, out var tooltip) ? tooltip : null);
+                    doc.GetValueOrDefault(match.Groups["parameter"].Value));
             }
         }
 
@@ -248,7 +248,7 @@ public static IEnumerable<HLSLFunctionParameter> Parse(string hlsl, Dictionary<s
     class HLSLFunction
     {
         // Match all attributes not followed by a single '=' character and also catch ++ and -- prefix (for read+write case)
-        static readonly string s_AttributeReadPattern = @"(?<op>\+\+|\-\-)?{0}.(?<name>\w+\b)(?!.*(?:[^=]=[^=]))";
+        static readonly string s_AttributeReadPattern = @"(?<op>\+{{2}}|-{{2}})?{0}.(?<name>\w+\b)(?!(?:\.\w+)?\s*[^=<>+-]=[^=])";
         // Match all attributes followed by an assigment operator (=, ++, --, +=, -= ...) even if there's multiple assignments on the same line
         private static readonly string s_AttributeWritePattern = @"{0}.(?<name>\w+)(?:\.\w)?\s*(?<op>[\/\-+*%&\|\^]?=[^=]|(\+\+|\-\-|<<=|>>=))";
         // Simply match lines where a 'return' statement is used

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

@@ -156,6 +156,36 @@ public void Check_CustomHLSL_Block_Attribute_Read_Access()
             Assert.IsTrue(hlslBlock.attributes.All(x => x.mode == VFXAttributeMode.Read));
         }
 
+        [Test, Description("Covers issue UUM-79389")]
+        public void Check_CustomHLSL_Block_Attribute_Read_SubField_Access()
+        {
+            // Arrange
+            var hlslCode =
+                "void Test(inout VFXAttributes attributes, in float value, in float altSize)\n" +
+                "{\n" +
+                "    if (attributes.position.y >= value)\n" +
+                "    {\n" +
+                "        attributes.size = altSize;\n" +
+                "    }\n" +
+                "}";
+
+            var hlslBlock = CreateCustomHLSLBlock();
+            hlslBlock.SetSettingValue("m_HLSLCode", hlslCode);
+
+            // Act
+            hlslBlock.Invalidate(VFXModel.InvalidationCause.kSettingChanged);
+
+            // Assert
+            Assert.AreEqual(2, hlslBlock.attributes.Count());
+            var sizeAttribute = hlslBlock.attributes.First();
+            Assert.AreEqual(sizeAttribute.attrib.name, "size");
+            Assert.AreEqual(sizeAttribute.mode, VFXAttributeMode.Write);
+
+            var positionAttribute = hlslBlock.attributes.Last();
+            Assert.AreEqual(positionAttribute.attrib.name, "position");
+            Assert.AreEqual(positionAttribute.mode, VFXAttributeMode.Read);
+        }
+
         [Test]
         public void Check_CustomHLSL_Block_Attribute_Write_Access()
         {

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

@@ -396,6 +396,30 @@ public void HLSL_Variadic_Attributes()
             Assert.AreEqual(1, errors.Length, "Missing error feedback when using variadic attribute in custom hlsl code");
             Assert.IsInstanceOf<HLSLVFXAttributeIsVariadic>(errors[0]);
         }
+
+        [Test, Description("Covers issue UUM-79389")]
+        public void HLSL_Parameters_On_Different_Lines()
+        {
+            // Arrange
+            var hlslCode =
+                "void CustomHLSL(inout VFXAttributes attributes" +
+                "  , in float3 offset" +
+                "  , in float speedFactor)" + "\n" +
+                "{" + "\n" +
+                "  attributes.position += offset;" + "\n" +
+                "  attributes.velocity *= speedFactor;" + "\n" +
+                "}";
+
+            // Act
+            var function = HLSLFunction.Parse(this.attributesManager, hlslCode).Single();
+
+            // Assert
+            Assert.AreEqual(3, function.inputs.Count);
+            Assert.AreEqual(new [] { "attributes", "offset", "speedFactor" }, function.inputs.Select(x => x.name));
+            Assert.AreEqual(new [] { "VFXAttributes", "float3", "float" }, function.inputs.Select(x => x.rawType));
+            Assert.AreEqual(new [] { HLSLAccess.INOUT, HLSLAccess.IN, HLSLAccess.IN }, function.inputs.Select(x => x.access));
+
+        }
     }
 }
 #endif