Merge pull request #1564 from json-api-dotnet/fix-operations-empty-result

Fixed: return empty object instead of data:null in operation results

Author: bkoelman

Diff for: src/JsonApiDotNetCore/Serialization/JsonConverters/WriteOnlyDocumentConverter.cs

@@ -61,7 +61,28 @@ public override void Write(Utf8JsonWriter writer, Document value, JsonSerializer
         if (!value.Results.IsNullOrEmpty())
         {
             writer.WritePropertyName(AtomicResultsText);
-            WriteSubTree(writer, value.Results, options);
+            writer.WriteStartArray();
+
+            foreach (AtomicResultObject result in value.Results)
+            {
+                writer.WriteStartObject();
+
+                if (result.Data.IsAssigned)
+                {
+                    writer.WritePropertyName(DataText);
+                    WriteSubTree(writer, result.Data, options);
+                }
+
+                if (!result.Meta.IsNullOrEmpty())
+                {
+                    writer.WritePropertyName(MetaText);
+                    WriteSubTree(writer, result.Meta, options);
+                }
+
+                writer.WriteEndObject();
+            }
+
+            writer.WriteEndArray();
         }
 
         if (!value.Errors.IsNullOrEmpty())

Diff for: test/JsonApiDotNetCoreTests/IntegrationTests/AtomicOperations/Mixed/AtomicSerializationTests.cs

@@ -101,9 +101,7 @@ await _testContext.RunOnDatabaseAsync(async dbContext =>
                 "self": "http://localhost/operations"
               },
               "atomic:results": [
-                {
-                  "data": null
-                },
+                {},
                 {
                   "data": {
                     "type": "textLanguages",