Enhance enumerable graph type determing

src/GraphQL.Conventions/Types/Resolution/Extensions/ReflectionExtensions.cs

@@ -30,6 +30,46 @@ public static bool IsNullableType(this TypeInfo type)
             return type.IsGenericType(typeof(Nullable<>));
         }
 
+        public static Type GetImplementationInterface(this Type type, Type interfaceType, bool fuseGeneric = true)
+        {
+            if (!interfaceType.IsInterface)
+                return null;
+
+            fuseGeneric &= interfaceType.IsGenericType;
+            if (type.IsGenericType && fuseGeneric
+                    ? type.GetGenericTypeDefinition() == interfaceType.GetGenericTypeDefinition()
+                    : type == interfaceType)
+            {
+                return interfaceType;
+            }
+
+            while (type is not null)
+            {
+                var interfaces = type.GetInterfaces();
+                var mayFusedGenericInterface = fuseGeneric
+                    ? interfaces.Select(t => t.IsGenericType ? t.GetGenericTypeDefinition() : t).ToArray()
+                    : interfaces;
+
+                for (int i = 0; i < interfaces.Length; i++)
+                {
+                    var @interface = interfaces[i];
+                    if (mayFusedGenericInterface[i] == interfaceType)
+                        return interfaces[i];
+                    var ni = @interface.GetImplementationInterface(interfaceType, fuseGeneric);
+                    if (ni is not null)
+                        return ni;
+                }
+
+                type = type.BaseType;
+            }
+
+            return null;
+        }
+
+        public static bool IsImplementingInterface(this Type type, Type interfaceType, bool fuseGeneric = true) =>
+            type.GetImplementationInterface(interfaceType, fuseGeneric) is not null;
+
+
         public static TypeInfo BaseType(this TypeInfo type)
         {
             return type.IsNullableType()
@@ -45,14 +85,19 @@ public static TypeInfo TypeParameter(this TypeInfo type)
             }
             return type.IsGenericType
                 ? type.GenericTypeArguments.First().GetTypeInfo()
-                : null;
+                : type.TypeParameterCollection();
         }
 
         public static TypeInfo TypeParameter(this GraphTypeInfo type)
         {
             return type.TypeRepresentation.TypeParameter();
         }
 
+        public static TypeInfo TypeParameterCollection(this TypeInfo type) => (
+            type.GetImplementationInterface(typeof(ICollection<>)) ??
+            type.GetImplementationInterface(typeof(IReadOnlyList<>))
+        )?.GetTypeInfo();
+
         public static bool IsPrimitiveGraphType(this TypeInfo type)
         {
             return type.IsPrimitive ||
@@ -63,8 +108,13 @@ public static bool IsPrimitiveGraphType(this TypeInfo type)
 
         public static bool IsEnumerableGraphType(this TypeInfo type)
         {
-            return type.IsGenericType(typeof(List<>)) ||
-                   type.IsGenericType(typeof(IList<>)) ||
+            if (type.IsImplementingInterface(typeof(IDictionary)) || type.IsImplementingInterface(typeof(IDictionary<,>)))
+            {
+                return false;
+            }
+
+            return type.IsImplementingInterface(typeof(ICollection<>)) ||
+                   type.IsImplementingInterface(typeof(IReadOnlyCollection<>)) ||
                    type.IsGenericType(typeof(IEnumerable<>)) ||
                    (type.IsGenericType && type.DeclaringType == typeof(Enumerable)) || // Handles internal Iterator implementations for LINQ; for reference https://referencesource.microsoft.com/#system.core/System/Linq/Enumerable.cs
                    type.IsArray;
@@ -93,16 +143,19 @@ public static TypeInfo GetTypeRepresentation(this TypeInfo typeInfo)
             {
                 typeInfo = typeInfo.TypeParameter();
             }
+
             if (typeInfo.IsGenericType(typeof(IObservable<>)))
             {
                 typeInfo = typeInfo.TypeParameter();
             }
+
             if (typeInfo.IsGenericType(typeof(Nullable<>)) ||
                 typeInfo.IsGenericType(typeof(NonNull<>)) ||
                 typeInfo.IsGenericType(typeof(Optional<>)))
             {
                 typeInfo = typeInfo.TypeParameter();
             }
+
             return typeInfo;
         }
 

test/GraphQL.Conventions.Tests/Types/Resolution/Extensions/ReflectionExtensionsTests.cs

@@ -0,0 +1,110 @@
+using System;
+using System.Collections;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Reflection;
+using GraphQL.Conventions.Types.Resolution.Extensions;
+using Xunit;
+
+namespace Tests.Types.Resolution.Extensions
+{
+    public class ReflectionExtensionsTests
+    {
+        [Theory]
+        [MemberData(nameof(IsEnumerableGraphType_Should_Return_True_For_Common_Collection_Types_Data))]
+        public void IsEnumerableGraphType_Should_Return_True_For_Common_Collection_Types(Type type)
+        {
+            Assert.IsTrue(type.GetTypeInfo().IsEnumerableGraphType());
+        }
+
+        public static TheoryData<Type> IsEnumerableGraphType_Should_Return_True_For_Common_Collection_Types_Data() => new()
+        {
+            typeof(IEnumerable<>),
+            typeof(ConcurrentQueue<>),
+            typeof(HashSet<>),
+            typeof(int[]),
+            typeof(List<>),
+            typeof(IList<>),
+            typeof(IReadOnlyList<>),
+            typeof(IReadOnlyCollection<>),
+        };
+
+        [Theory]
+        [MemberData(nameof(IsEnumerableGraphType_Should_Return_False_For_Common_Dictionary_Types_Data))]
+        public void IsEnumerableGraphType_Should_Return_False_For_Common_Dictionary_Types(Type type)
+        {
+            Assert.IsFalse(type.GetTypeInfo().IsEnumerableGraphType());
+        }
+
+        public static TheoryData<Type> IsEnumerableGraphType_Should_Return_False_For_Common_Dictionary_Types_Data() => new()
+        {
+            typeof(IDictionary<,>),
+            typeof(IDictionary),
+        };
+
+        [Theory]
+        [MemberData(nameof(GetImplementationInterface_WithoutFuse_AcquireSpecifiedInterfaceOnly_Data))]
+        public void GetImplementationInterface_WithoutFuse_AcquireSpecifiedInterfaceOnly(Type type, Type assignableInterface)
+            => Assert.IsTrue(type.IsImplementingInterface(assignableInterface, false));
+
+        public static TheoryData<Type, Type> GetImplementationInterface_WithoutFuse_AcquireSpecifiedInterfaceOnly_Data() =>
+            new()
+            {
+                { typeof(ITestInterface1<int>), typeof(ITestInterface1<int>) },
+                { typeof(ITestInterface2<int>), typeof(ITestInterface1<int>) },
+                { typeof(ITestInterface2<int>), typeof(ITestInterface2<int>) },
+                { typeof(TestClass11<int>), typeof(ITestInterface1<int>) },
+                { typeof(TestClass12), typeof(ITestInterface1<string>) },
+                { typeof(TestClass12), typeof(ITestInterface2<string>) },
+                { typeof(TestClass2), typeof(ITestInterface1<int>) },
+                { typeof(TestClass2), typeof(ITestInterface1<string>) },
+                { typeof(TestClass2), typeof(ITestInterface2<string>) },
+            };
+
+        [Theory]
+        [MemberData(nameof(GetImplementationInterface_WithFuse_AcquireSpecifiedInterfaceOnly_Data))]
+        public void GetImplementationInterface_WithFuse_AcquireSpecifiedInterfaceOnly(Type type, Type assignableInterface) =>
+            Assert.IsTrue(type.IsImplementingInterface(assignableInterface));
+
+        public static TheoryData<Type, Type> GetImplementationInterface_WithFuse_AcquireSpecifiedInterfaceOnly_Data() =>
+            new()
+            {
+                { typeof(ITestInterface1<int>), typeof(ITestInterface1<>) },
+                { typeof(ITestInterface2<int>), typeof(ITestInterface1<>) },
+                { typeof(ITestInterface2<int>), typeof(ITestInterface2<>) },
+                { typeof(TestClass11<int>), typeof(ITestInterface1<>) },
+                //
+                { typeof(ITestInterface1<string>), typeof(ITestInterface1<>) },
+                { typeof(ITestInterface2<string>), typeof(ITestInterface1<>) },
+                { typeof(ITestInterface2<string>), typeof(ITestInterface2<>) },
+                { typeof(TestClass11<string>), typeof(ITestInterface1<>) },
+                //
+                { typeof(TestClass12), typeof(ITestInterface1<>) },
+                { typeof(TestClass12), typeof(ITestInterface2<>) },
+                { typeof(TestClass2), typeof(ITestInterface1<>) },
+                { typeof(TestClass2), typeof(ITestInterface2<>) },
+            };
+
+        private interface ITestInterface1<out T>
+        {
+            // ReSharper disable once UnusedMember.Global
+            T Item => throw new NotImplementedException();
+        }
+
+        private interface ITestInterface2<out T> : ITestInterface1<T>
+        {
+        }
+
+        private class TestClass11<T> : ITestInterface1<T>
+        {
+        }
+
+        private class TestClass12 : ITestInterface2<string>
+        {
+        }
+
+        private class TestClass2 : ITestInterface2<string>, ITestInterface1<int>
+        {
+        }
+    }
+}