graphql-dotnet#529 adding support for IEnumerable type arguments other than generic lists (graphql-dotnet#533)

Author: landbolts

src/GraphQL.Tests/Builders/FieldBuilderTests.cs

@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Linq;
 using GraphQL.StarWars.Types;
 using GraphQL.Types;
@@ -331,6 +332,30 @@ public void can_get_list_argument()
             });
         }
 
+        [Fact]
+        public void can_get_collection_argument()
+        {
+            var objectType = new ObjectGraphType();
+            objectType.Field<StringGraphType>()
+                .Argument<NonNullGraphType<ListGraphType<NonNullGraphType<StringGraphType>>>>("episodes", "episodes")
+                .Resolve(context =>
+                {
+                    context.GetArgument<Collection<string>>("episodes").ShouldBe(new Collection<string> { "JEDI", "EMPIRE" });
+                    return null;
+                });
+
+            var field = objectType.Fields.First();
+            field.Resolver.Resolve(new ResolveFieldContext
+            {
+                Arguments = new Dictionary<string, object>
+                {
+                    {"episodes", new object[] {"JEDI", "EMPIRE" } }
+                },
+                FieldDefinition = field
+            });
+        }
+
+
         [Fact]
         public void getting_specified_argument_in_resolver_overrides_default_value()
         {

src/GraphQL/ObjectExtensions.cs

@@ -56,10 +56,20 @@ public static object GetPropertyValue(this object propertyValue, Type fieldType)
             if (fieldType.Name != "String"
                 && enumerableInterface != null)
             {
+                IList newArray;
                 var elementType = enumerableInterface.GetGenericArguments()[0];
                 var underlyingType = Nullable.GetUnderlyingType(elementType) ?? elementType;
-                var genericListType = typeof(List<>).MakeGenericType(elementType);
-                var newArray = (IList) Activator.CreateInstance(genericListType);
+                var implementsIList = fieldType.GetInterface("IList") != null;
+
+                if (implementsIList)
+                {
+                    newArray = (IList)Activator.CreateInstance(fieldType);
+                }
+                else
+                {
+                    var genericListType = typeof(List<>).MakeGenericType(elementType);
+                    newArray = (IList)Activator.CreateInstance(genericListType);
+                }
 
                 var valueList = propertyValue as IEnumerable;
                 if (valueList == null) return newArray;