UserProfile.Fields left empty when deserializing an empty array

Fixes #15

SlackNet.Tests/SerializationTests.cs

@@ -127,6 +127,31 @@ public void IgnoreIfDefault_NotDefault_Serialized()
             result.ShouldBe(@"{""value"":""test_value""}");
         }
 
+        [Test]
+        public void UserProfileFields_Null_IsNull()
+        {
+            var result = JsonConvert.DeserializeObject<UserProfile>(@"{""fields"":null,""phone"":""123""}");
+            result.Fields.ShouldBeNull();
+            result.Phone.ShouldBe("123");
+        }
+
+        [Test]
+        public void UserProfileFields_EmptyArray_IsEmpty()
+        {
+            var result = JsonConvert.DeserializeObject<UserProfile>(@"{""fields"":[],""phone"":""123""}");
+            result.Fields.ShouldBeEmpty();
+            result.Phone.ShouldBe("123");
+        }
+
+        [Test]
+        public void UserProfileFields_PopulatedObject_IsPopulated()
+        {
+            var result = JsonConvert.DeserializeObject<UserProfile>(@"{""fields"":{""fieldId"":{""value"":""foo""}},""phone"":""123""}");
+            result.Fields.Keys.ShouldMatch(new[] { "fieldId" });
+            result.Fields["fieldId"].Value.ShouldBe("foo");
+            result.Phone.ShouldBe("123");
+        }
+
         class SimpleType
         {
             public string SomeProperty { get; set; }

SlackNet/Objects/UserProfile.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using Newtonsoft.Json;
 
 namespace SlackNet
 {
@@ -21,6 +22,7 @@ public class UserProfile
         public string Image72 { get; set; }
         public string Image192 { get; set; }
         public string Image512 { get; set; }
+        [JsonConverter(typeof(IgnoreArrayConverter))] // Slack returns an empty array instead of an object if profile has been modified, but no custom fields have been set
         public IDictionary<string, UserProfileField> Fields { get; set; } = new Dictionary<string, UserProfileField>();
     }
 }

SlackNet/Serialization/IgnoreArrayConverter.cs

@@ -0,0 +1,31 @@
+using System;
+using System.Collections.Generic;
+using System.Reflection;
+using Newtonsoft.Json;
+
+namespace SlackNet
+{
+    class IgnoreArrayConverter : JsonConverter
+    {
+        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
+        {
+            serializer.Serialize(writer, value);
+        }
+
+        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
+        {
+            if (reader.TokenType == JsonToken.StartArray)
+            {
+                reader.Skip();
+                return existingValue;
+            }
+
+            return serializer.Deserialize(reader, objectType);
+        }
+
+        public override bool CanConvert(Type objectType)
+        {
+            return typeof(IDictionary<,>).GetTypeInfo().IsAssignableFrom(objectType.GetTypeInfo());
+        }
+    }
+}