Add direct support for structs (#710)

sebastienros · Nov 6, 2024 · 2c2c578 · 2c2c578
1 parent 545aa83
commit 2c2c578
Show file tree

Hide file tree

Showing 5 changed files with 90 additions and 11 deletions.
diff --git a/Directory.Packages.props b/Directory.Packages.props
@@ -8,18 +8,16 @@
     <PackageVersion Include="Parlot" Version="1.0.2" />
     <PackageVersion Include="System.Text.Json" Version="8.0.5" />
     <PackageVersion Include="TimeZoneConverter" Version="6.1.0" />
-
+    <PackageVersion Include="System.Reflection.Emit.Lightweight" Version="4.7.0" />
     <!-- Benchmarks -->
     <PackageVersion Include="BenchmarkDotNet" Version="0.14.0" />
     <PackageVersion Include="DotLiquid" Version="2.2.692" />
     <PackageVersion Include="Liquid.NET" Version="0.10.0" />
     <PackageVersion Include="Scriban" Version="5.11.0" />
     <PackageVersion Include="Handlebars.Net" Version="2.1.6" />
-
     <!-- Global Package References -->
     <GlobalPackageReference Include="Microsoft.SourceLink.GitHub" Version="8.0.0" PrivateAssets="all" />
     <GlobalPackageReference Include="PolySharp" Version="1.14.1" PrivateAssets="all" />
-
     <!-- Testing -->
     <PackageVersion Include="Newtonsoft.Json" Version="13.0.3" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.11.1" />

diff --git a/Fluid.Tests/Domain/CustomStruct.cs b/Fluid.Tests/Domain/CustomStruct.cs
@@ -0,0 +1,23 @@
+namespace Fluid.Tests.Domain
+{
+    public struct CustomStruct
+    {
+        public int X1 { get; set; }
+
+        private int _x2;
+
+        public int X2
+        {
+            get { return _x2; }
+            set { _x2 = value; }
+        }
+
+        private int x3;
+
+        public int X3
+        {
+            get { return x3; }
+            set { x3 = value; }
+        }
+    }
+}
diff --git a/Fluid.Tests/MemberAccessStrategyTests.cs b/Fluid.Tests/MemberAccessStrategyTests.cs
@@ -257,13 +257,9 @@ public void ShouldResolveEnums()
         [Fact]
         public void ShouldResolveStructs()
         {
-            // We can't create an open delegate on a Struc (dotnet limitation?), so instead create custom delegates
-            // https://sharplab.io/#v2:EYLgtghglgdgNAFxAJwK7wCYgNQB8ACATAAwCwAUEQIwX7EAE+VAdACLIQDusA5gNwUKANwjJ6ABwCSMAGYB7egF56CAJ7iApnJkAKAApzYCAJTMA4hoR7kczcjU6ARAA1HxgeRFiMhJROny5pYWCACylgAWchg6pgDCyBoQCBqsGgA2GjzJGjpqmto6+ACsADwGRnD0RgB8xu4UQA==
-
             var options = new TemplateOptions();
             options.MemberAccessStrategy.Register<Shape>();
-            options.MemberAccessStrategy.Register<Point>(nameof(Point.X), new DelegateAccessor<Point, int>((point, name, context) => point.X));
-            options.MemberAccessStrategy.Register<Point>(nameof(Point.Y), new DelegateAccessor<Point, int>((point, name, context) => point.Y));
+            options.MemberAccessStrategy.Register<Point>();
 
             var circle = new Shape
             {
@@ -273,6 +269,23 @@ public void ShouldResolveStructs()
             var template = _parser.Parse("{{Coordinates.X}} {{Coordinates.Y}}");
             Assert.Equal("1 2", template.Render(new TemplateContext(circle, options, false)));
         }
+
+        [Fact]
+        public void ShouldFindBackingFields()
+        {
+            var options = new TemplateOptions();
+            options.MemberAccessStrategy.Register<CustomStruct>();
+
+            var s = new CustomStruct
+            {
+                X1 = 1,
+                X2 = 2,
+                X3 = 3
+            };
+
+            var template = _parser.Parse("{{X1}} {{X2}} {{X3}}");
+            Assert.Equal("1 2 3", template.Render(new TemplateContext(s, options, false)));
+        }
     }
 
     public class Class1

diff --git a/Fluid/Accessors/PropertyInfoAccessor.cs b/Fluid/Accessors/PropertyInfoAccessor.cs
@@ -1,4 +1,5 @@
 using System.Reflection;
+using System.Reflection.Emit;
 
 namespace Fluid.Accessors
 {
@@ -8,16 +9,59 @@ public sealed class PropertyInfoAccessor : IMemberAccessor
 
         public PropertyInfoAccessor(PropertyInfo propertyInfo)
         {
-            var delegateType = typeof(Func<,>).MakeGenericType(propertyInfo.DeclaringType, propertyInfo.PropertyType);
-            var d = propertyInfo.GetGetMethod().CreateDelegate(delegateType);
+            Delegate d;
+
+            if (!propertyInfo.DeclaringType.IsValueType)
+            {
+                var delegateType = typeof(Func<,>).MakeGenericType(propertyInfo.DeclaringType, propertyInfo.PropertyType);
+                d = propertyInfo.GetGetMethod().CreateDelegate(delegateType);
+            }
+            else
+            {
+                // We can't create an open delegate on a struct (dotnet limitation?), so instead create custom delegates
+                // https://sharplab.io/#v2:EYLgtghglgdgNAFxAJwK7wCYgNQB8ACATAAwCwAUEQIwX7EAE+VAdACLIQDusA5gNwUKANwjJ6ABwCSMAGYB7egF56CAJ7iApnJkAKAApzYCAJTMA4hoR7kczcjU6ARAA1HxgeRFiMhJROny5pYWCACylgAWchg6pgDCyBoQCBqsGgA2GjzJGjpqmto6+ACsADwGRnD0RgB8xu4UQA==
+                // Instead we generate IL to access the backing field directly
+
+                d = GetGetter(propertyInfo.DeclaringType, propertyInfo.Name);
+            }
+
+            if (d == null)
+            {
+                _invoker = null;
+            }
 
             var invokerType = typeof(Invoker<,>).MakeGenericType(propertyInfo.DeclaringType, propertyInfo.PropertyType);
             _invoker = Activator.CreateInstance(invokerType, [d]) as IInvoker;
         }
 
         public object Get(object obj, string name, TemplateContext ctx)
         {
-            return _invoker.Invoke(obj);
+            return _invoker?.Invoke(obj);
+        }
+
+        private static Delegate GetGetter(Type declaringType, string fieldName)
+        {
+            string[] names = [fieldName.ToLowerInvariant(), $"<{fieldName}>k__BackingField", "_" + fieldName.ToLowerInvariant()];
+
+            var field = names
+                .Select(n => declaringType.GetField(n, BindingFlags.Instance | BindingFlags.NonPublic))
+                .FirstOrDefault(x => x != null);
+
+            if (field == null)
+            {
+                return null;
+            }
+
+            var parameterTypes = new[] { typeof(object), declaringType };
+
+            var method = new DynamicMethod(fieldName + "Get", field.FieldType, parameterTypes, typeof(PropertyInfoAccessor).Module, true);
+
+            var emitter = method.GetILGenerator();
+            emitter.Emit(OpCodes.Ldarg_1);
+            emitter.Emit(OpCodes.Ldfld, field);
+            emitter.Emit(OpCodes.Ret);
+
+            return method.CreateDelegate(typeof(Func<,>).MakeGenericType(declaringType, field.FieldType));
         }
 
         private interface IInvoker

diff --git a/Fluid/Fluid.csproj b/Fluid/Fluid.csproj
@@ -34,6 +34,7 @@
   <ItemGroup Condition="'$(TargetFramework)'=='netstandard2.0'">
     <PackageReference Include="System.Text.Json" />
     <PackageReference Include="Microsoft.CSharp" />
+    <PackageReference Include="System.Reflection.Emit.Lightweight" />
   </ItemGroup>
 
   <!-- Keep specific targets since it removes some dependencies -->