Issue #101, nullable embedded lists

Author: kbrichan

WebApi.Hal.Tests/HalResourceMixedContentTest.cs

@@ -1,4 +1,5 @@
-using System.IO;
+using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using System.Net.Http;
 using System.Text;
@@ -19,6 +20,7 @@ public HalResourceMixedContentTest()
             {
                 Boss = new Boss(2, "Eunice PHB", 1, true)
             };
+            resource.People = new List<Person>();
             resource.People.Add(new Person(3, "Dilbert", 1));
             resource.People.Add(new Person(4, "Wally", 1));
             resource.People.Add(new Person(5, "Alice", 1));
@@ -214,6 +216,35 @@ public void peopledetail_post_json_embedded_arrays_test()
             }
         }
 
+        [Fact]
+        public void peopledetail_post_json_embedded_null_test()
+        {
+            // arrange
+            var mediaFormatter = new JsonHalMediaTypeFormatter { Indent = true };
+            var type = typeof(OrganisationWithPeopleDetailRepresentation);
+            const string json = @"
+{
+""Id"":""3"",
+""Name"": ""Singles Dept.""
+}
+";
+
+            // act
+            using (
+                var stream = new MemoryStream(Encoding.UTF8.GetBytes(json))
+                )
+            {
+                var obj = mediaFormatter.ReadFromStreamAsync(type, stream, null, null).Result;
+
+                // assert
+                Assert.NotNull(obj);
+                var org = obj as OrganisationWithPeopleDetailRepresentation;
+                Assert.NotNull(org);
+                Assert.Null(org.Boss);
+                Assert.Null(org.People);
+            }
+        }
+
         class MySimpleList : SimpleListRepresentation<OrganisationRepresentation>
         {
             protected override void CreateHypermedia()

WebApi.Hal.Tests/Representations/OrganisationWithPeopleDetailRepresentation.cs

@@ -64,13 +64,12 @@ public OrganisationWithPeopleDetailRepresentation(int id, string name)
         {
             Id = id;
             Name = name;
-            People = new List<Person>();
         }
 
         public int Id { get; set; }
         public string Name { get; set; }
 
-        public List<Person> People { get; set; }
+        public IList<Person> People { get; set; }
         public Boss Boss { get; set; }
 
         public override string Rel

WebApi.Hal.Web/Api/BeerDetailController.cs

@@ -1,4 +1,5 @@
-using System.Linq;
+using System.Collections.Generic;
+using System.Linq;
 using System.Web.Http;
 using WebApi.Hal.Web.Api.Resources;
 using WebApi.Hal.Web.Data;
@@ -37,8 +38,12 @@ public BeerDetailRepresentation Get(int id)
                 Style = new BeerStyleRepresentation {Id = beer.Style.Id, Name = beer.Style.Name},
                 Brewery = new BreweryRepresentation {Id = beer.Brewery.Id, Name = beer.Brewery.Name}
             };
-            foreach (var review in reviews)
-                detail.Reviews.Add(review);
+            if (reviews.Count > 0)
+            {
+                detail.Reviews = new List<ReviewRepresentation>();
+                foreach (var review in reviews)
+                    detail.Reviews.Add(review);
+            }
             return detail;
         }
 

WebApi.Hal.Web/Api/Resources/BeerDetailRepresentation.cs

@@ -4,11 +4,6 @@ namespace WebApi.Hal.Web.Api.Resources
 {
     public class BeerDetailRepresentation : Representation
     {
-        public BeerDetailRepresentation()
-        {
-            Reviews = new List<ReviewRepresentation>();
-        }
-
         public int Id { get; set; }
         public string Name { get; set; }
 

WebApi.Hal/JsonConverters/ResourceConverter.cs

@@ -95,16 +95,27 @@ static IResource CreateResource(JObject jObj, Type resourceType)
                 foreach (var prop in resourceType.GetProperties().Where(p => Representation.IsEmbeddedResourceType(p.PropertyType)))
                 {
                     // expects embedded collection of resources is implemented as an IList on the Representation-derived class
-                    var lst = prop.GetValue(resource) as IList;
-                    if (lst != null)
+                    if (typeof (IEnumerable<IResource>).IsAssignableFrom(prop.PropertyType))
                     {
+                        var lst = prop.GetValue(resource) as IList;
+                        if (lst == null)
+                        {
+                            lst = ConstructResource(prop.PropertyType) as IList ??
+                                  Activator.CreateInstance(
+                                      typeof (List<>).MakeGenericType(prop.PropertyType.GenericTypeArguments)) as IList;
+                            if (lst == null) continue;
+                            prop.SetValue(resource, lst);
+                        }
                         if (prop.PropertyType.GenericTypeArguments != null &&
                             prop.PropertyType.GenericTypeArguments.Length > 0)
                             CreateEmbedded(embeddeds, prop.PropertyType.GenericTypeArguments[0],
                                 newRes => lst.Add(newRes));
                     }
                     else
-                        CreateEmbedded(embeddeds, prop.PropertyType, newRes => prop.SetValue(resource, newRes));
+                    {
+                        var prop1 = prop;
+                        CreateEmbedded(embeddeds, prop.PropertyType, newRes => prop1.SetValue(resource, newRes));
+                    }
                 }
             }
 
@@ -177,22 +188,7 @@ static string GetResourceTypeRel(Type resourceType)
                 {
                     if (ResourceTypeToRel.ContainsKey(resourceType.FullName))
                         return ResourceTypeToRel[resourceType.FullName];
-                    // favor c-tor with zero params, but if it doesn't exist, use c-tor with fewest params and pass all null values
-                    var ctors = resourceType.GetConstructors();
-                    ConstructorInfo useThisCtor = null;
-                    foreach (var ctor in ctors)
-                    {
-                        if (ctor.GetParameters().Length == 0)
-                        {
-                            useThisCtor = ctor;
-                            break;
-                        }
-                        if (useThisCtor == null || useThisCtor.GetParameters().Length > ctor.GetParameters().Length)
-                            useThisCtor = ctor;
-                    }
-                    if (useThisCtor == null) return string.Empty;
-                    var ctorParams = new object[useThisCtor.GetParameters().Length];
-                    var res = useThisCtor.Invoke(ctorParams) as IResource;
+                    var res = ConstructResource(resourceType) as IResource;
                     if (res != null)
                     {
                         var rel = res.Rel;
@@ -208,6 +204,26 @@ static string GetResourceTypeRel(Type resourceType)
             }
         }
 
+        static object ConstructResource(Type resourceType)
+        {
+            // favor c-tor with zero params, but if it doesn't exist, use c-tor with fewest params and pass all null values
+            var ctors = resourceType.GetConstructors();
+            ConstructorInfo useThisCtor = null;
+            foreach (var ctor in ctors)
+            {
+                if (ctor.GetParameters().Length == 0)
+                {
+                    useThisCtor = ctor;
+                    break;
+                }
+                if (useThisCtor == null || useThisCtor.GetParameters().Length > ctor.GetParameters().Length)
+                    useThisCtor = ctor;
+            }
+            if (useThisCtor == null) return null;
+            var ctorParams = new object[useThisCtor.GetParameters().Length];
+            return useThisCtor.Invoke(ctorParams);
+        }
+
         public override bool CanConvert(Type objectType)
         {
             return IsResource(objectType) && !IsResourceList(objectType);