Improve introspection support

GraphQL.Net/DynamicTypeBuilder.cs

@@ -1,7 +1,10 @@
 using System;
+using System.CodeDom;
 using System.Collections.Generic;
+using System.Linq;
 using System.Reflection;
 using System.Reflection.Emit;
+using GraphQL.Parser;
 
 namespace GraphQL.Net
 {
@@ -17,45 +20,106 @@ static DynamicTypeBuilder()
             ModuleBuilder = assemblyBuilder.DefineDynamicModule(AssemblyName + ".dll");
         }
 
-        public static Type CreateDynamicType(string name, Dictionary<string, Type> properties)
+        public static Type CreateDynamicType(string name, IEnumerable<GraphQLField> fields)
         {
             var typeBuilder = ModuleBuilder.DefineType(AssemblyName + "." + name,
                 TypeAttributes.Public | TypeAttributes.Class | TypeAttributes.AutoClass | TypeAttributes.AnsiClass | TypeAttributes.Serializable | TypeAttributes.BeforeFieldInit);
+
+            var graphQlFields = fields as GraphQLField[] ?? fields.ToArray();
+            if (graphQlFields.Count() != graphQlFields.Select(f => f.Name).Distinct().Count())
+            {
+                var firstDuplicatedFieldName = graphQlFields.GroupBy(f => f.Name)
+                    .Where(g => g.Count() > 1)
+                    .Select(g => g.Key)
+                    .FirstOrDefault();
+                throw new Exception("Duplicated field name '" + firstDuplicatedFieldName + "' on type '" + name + "'.");
+            }
+            var properties = ConvertFieldsToProperties(graphQlFields);
             foreach (var prop in properties)
                 CreateProperty(typeBuilder, prop.Key, prop.Value);
             return typeBuilder.CreateType();
         }
 
-        private static void CreateProperty(TypeBuilder typeBuilder, string name, Type type)
+        public static Type CreateDynamicUnionTypeOrInterface(string name, IEnumerable<GraphQLField> fields,
+            IEnumerable<GraphQLType> possibleTypes, Func<string, string, string> createPossibleTypePropertyName)
         {
-            var fieldBuilder = typeBuilder.DefineField("_" + name.ToLower(), type, FieldAttributes.Private);
-            var propertyBuilder = typeBuilder.DefineProperty(name, PropertyAttributes.HasDefault, type, null);
+            var typeBuilder = ModuleBuilder.DefineType(AssemblyName + "." + name,
+                TypeAttributes.Public | TypeAttributes.Class | TypeAttributes.AutoClass | TypeAttributes.AnsiClass |
+                TypeAttributes.Serializable | TypeAttributes.BeforeFieldInit);
+            // Create an union type containing all properties of its possible types.
+            // Prefix all properties of a possible type to avoid conflicts of property names
+            var subTypeProperties = possibleTypes
+                .SelectMany(
+                    t => t.Fields.Select(f => new {Name = createPossibleTypePropertyName(t.Name, f.Name), Type = GetFieldPropertyType(f)}));
+            var properties =
+                subTypeProperties.Concat(fields.Select(f => new {Name = f.Name, Type = GetFieldPropertyType(f)}));
+            foreach (var prop in properties)
+                CreateProperty(typeBuilder, prop.Name, prop.Type);
 
-            propertyBuilder.SetGetMethod(CreateGetMethod(typeBuilder, fieldBuilder, name, type));
-            propertyBuilder.SetSetMethod(CreateSetMethod(typeBuilder, fieldBuilder, name, type));
+            return typeBuilder.CreateType();
+        }
+
+        private static Type GetFieldPropertyType(GraphQLField field)
+        {
+            return field.Type.TypeKind == TypeKind.SCALAR
+                ? (field.IsList
+                    ? typeof(IEnumerable<>).MakeGenericType(field.Type.CLRType)
+                    : TypeHelpers.MakeNullable(field.Type.CLRType))
+                : typeof(object);
+        }
+
+        private static IDictionary<string, Type> ConvertFieldsToProperties(IEnumerable<GraphQLField> fields)
+        {
+            return fields.Where(f => !f.IsPost).ToDictionary(f => f.Name, GetFieldPropertyType);
         }
 
-        const MethodAttributes MethodAttrs = MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.HideBySig;
-        private static MethodBuilder CreateGetMethod(TypeBuilder typeBuilder, FieldInfo fieldBuilder, string name, Type type)
+        private static void CreateProperty(TypeBuilder typeBuilder, string name, Type type, bool isAbstract = false)
         {
+            FieldBuilder fieldBuilder = null;
+            if (!isAbstract) { 
+                fieldBuilder = typeBuilder.DefineField("_" + name.ToLower(), type, FieldAttributes.Private);
+            }
+            var propertyBuilder = typeBuilder.DefineProperty(name, PropertyAttributes.HasDefault, type, null);
+            propertyBuilder.SetGetMethod(CreateGetMethod(typeBuilder, fieldBuilder, name, type, isAbstract));
+            propertyBuilder.SetSetMethod(CreateSetMethod(typeBuilder, fieldBuilder, name, type, isAbstract));
+        }
+
+        const MethodAttributes MethodAttrs = MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.Virtual | MethodAttributes.HideBySig;
+
+        private static MethodBuilder CreateGetMethod(TypeBuilder typeBuilder, FieldInfo fieldBuilder, string name,
+            Type type, bool isAbstract)
+        {
+            if (isAbstract)
+            {
+                return typeBuilder.DefineMethod("get_" + name, MethodAttributes.Virtual | MethodAttributes.Abstract | MethodAttributes.Public, type, Type.EmptyTypes);
+            }
+
             var methodBuilder = typeBuilder.DefineMethod("get_" + name, MethodAttrs, type, Type.EmptyTypes);
             var generator = methodBuilder.GetILGenerator();
             generator.Emit(OpCodes.Ldarg_0);
             generator.Emit(OpCodes.Ldfld, fieldBuilder);
             generator.Emit(OpCodes.Ret);
-
+            
             return methodBuilder;
         }
 
-        private static MethodBuilder CreateSetMethod(TypeBuilder typeBuilder, FieldInfo fieldBuilder, string name, Type type)
+        private static MethodBuilder CreateSetMethod(TypeBuilder typeBuilder, FieldInfo fieldBuilder, string name, Type type, 
+            bool isAbstract)
         {
-            var methodBuilder = typeBuilder.DefineMethod("set" + name, MethodAttrs, null, new[] { type });
-            var generator = methodBuilder.GetILGenerator();
-            generator.Emit(OpCodes.Ldarg_0);
-            generator.Emit(OpCodes.Ldarg_1);
-            generator.Emit(OpCodes.Stfld, fieldBuilder);
-            generator.Emit(OpCodes.Ret);
-
+            var attrs = MethodAttrs;
+            if (isAbstract)
+            {
+                attrs = attrs | MethodAttributes.Abstract | MethodAttributes.Virtual;
+            }
+            var methodBuilder = typeBuilder.DefineMethod("set" + name, attrs, null, new[] { type });
+            if (!isAbstract)
+            {
+                var generator = methodBuilder.GetILGenerator();
+                generator.Emit(OpCodes.Ldarg_0);
+                generator.Emit(OpCodes.Ldarg_1);
+                generator.Emit(OpCodes.Stfld, fieldBuilder);
+                generator.Emit(OpCodes.Ret);
+            }
             return methodBuilder;
         }
     }