fix DynamoDBContext.FromDocument to handle nulls

Author: muhammad-othman

sdk/src/Services/DynamoDBv2/Custom/Conversion/DynamoDBEntryConversion.cs

@@ -573,11 +573,12 @@ public bool TryFromEntry(DynamoDBEntry entry, Type targetType, out object value)
             if (d != null && TryFrom(d, targetType, out value))
                 return true;
 
-            //var n = entry as DynamoDBNull;
-            //if (n != null)
-            //    return null;
-
             value = null;
+
+            var n = entry as DynamoDBNull;
+            if (n != null)
+                return true;
+
             return false;
         }
 

sdk/src/Services/DynamoDBv2/Custom/DataModel/ContextInternal.cs

@@ -370,6 +370,9 @@ private object FromDynamoDBEntry(SimplePropertyStorage propertyStorage, DynamoDB
                 return conversion.ConvertFromEntry(targetType, entry);
             else
             {
+                if (entry is DynamoDBNull)
+                    return null;
+
                 object output;
                 Document document = entry as Document;
                 if (document != null)

sdk/test/Services/DynamoDBv2/UnitTests/Custom/DynamoDBTests.cs

@@ -11,6 +11,7 @@
 using Amazon.DynamoDBv2.DocumentModel;
 using Amazon.DynamoDBv2.DataModel;
 using Amazon.DynamoDBv2.Model;
+using Amazon.DynamoDBv2;
 using ThirdParty.Json.LitJson;
 
 using Moq;
@@ -243,6 +244,72 @@ public void TestExplicitNullPropertyOnDocument()
             Assert.IsNull(doc["Name"].AsPrimitive().Value);
         }
 
+        [TestMethod]
+        [TestCategory("DynamoDBv2")]
+        public void TestFromJsonCanHandleAllDateTypes()
+        {
+            var json = @"
+                {
+                  ""StringValue"": ""test string"",
+                  ""BoolValue"": true,
+                  ""IntValue"": 200,
+                  ""DateValue"": ""2022-12-29T12:46:14.097Z"",
+                  ""NullableBoolValue"": null,
+                  ""NullableIntValue"": null,
+                  ""NullableDateValue"": null,
+                  ""SubData"": null,
+                  ""SubData2"": {
+                    ""StringValue"": null,
+                    ""NullableBoolValue"": false,
+                    ""NullableIntValue"": 500,
+                    ""NullableDateValue"": ""2022-12-28T12:46:14.097Z""
+                  }
+                }";
+
+            using (var dbClient = new AmazonDynamoDBClient())
+            using (var context = new DynamoDBContext(dbClient))
+            {
+                var document = Document.FromJson(json);
+                var container = context.FromDocument<DataContainer>(document);
+
+                Assert.IsNotNull(container);
+                Assert.AreEqual(container.StringValue, "test string");
+                Assert.AreEqual(container.BoolValue, true);
+                Assert.AreEqual(container.IntValue, 200);
+                Assert.AreEqual(container.DateValue, DateTime.Parse("2022-12-29T12:46:14.097Z"));
+                Assert.IsNull(container.NullableBoolValue);
+                Assert.IsNull(container.NullableIntValue);
+                Assert.IsNull(container.NullableDateValue);
+                Assert.IsNull(container.SubData);
+                Assert.IsNotNull(container.SubData2);
+                Assert.IsNull(container.SubData2.StringValue);
+                Assert.IsNotNull(container.SubData2.NullableIntValue);
+            }
+        }
+
+        public class DataContainer
+        {
+            public string StringValue { get; set; }
+            public bool BoolValue { get; set; }
+            public int IntValue { get; set; }
+            public DateTime DateValue { get; set; }
+
+            public bool? NullableBoolValue { get; set; }
+            public int? NullableIntValue { get; set; }
+            public DateTime? NullableDateValue { get; set; }
+
+            public SubContainer SubData { get; set; }
+            public SubContainer SubData2 { get; set; }
+
+            public class SubContainer
+            {
+                public string StringValue { get; set; }
+                public bool? NullableBoolValue { get; set; }
+                public int? NullableIntValue { get; set; }
+                public DateTime? NullableDateValue { get; set; }
+            }
+        }
+
 #if ASYNC_AWAIT
         [TestMethod]
         [TestCategory("DynamoDBv2")]