No Nulls.

openapi-diff/src/modeler/AutoRest.Swagger.Tests/SwaggerModelerCompareTests.cs

@@ -225,8 +225,9 @@ public void AddedPaths()
             var output = x.GetValidationMessagesAsJson();
             var raw = JToken.Parse(output);
             Assert.Equal(JTokenType.Object, raw.Type);
-            Assert.Equal("new/added_path.json:31:15", raw["location-new"].Value<string>());
-            Assert.Equal("paths./api/Operations.post", raw["jsonpath-new"].Value<string>());
+            Assert.Equal("new/added_path.json:31:15", raw["new"]["location"].Value<string>());
+            Assert.Equal("paths./api/Operations.post", raw["new"]["path"].Value<string>());
+            Assert.Null(raw["old"]["location"]);
         }
 
         /// <summary>

openapi-diff/src/modeler/AutoRest.Swagger/ComparisonMessage.cs

@@ -101,7 +101,7 @@ private static string Location(IJsonDocument jsonDoc, JToken jsonToken)
             // up cast.
             IJsonLineInfo x = jsonToken;
             return x == null ? 
-                "" : 
+                null : 
                 $"{ObjectPath.FileNameNorm(jsonDoc.FileName)}:{x.LineNumber}:{x.LinePosition}";
         }
 
@@ -111,23 +111,33 @@ private static string Location(IJsonDocument jsonDoc, JToken jsonToken)
 
         public string GetValidationMessagesAsJson()
         {
-            var rawMessage = new Dictionary<string, string>
+            var rawMessage = new JsonComparisonMessage
             {
-                ["id"] = Id.ToString(),
-                ["code"] = Code.ToString(),
-                ["message"] = Message,
-                ["jsonref-old"] = OldJsonRef,
-                ["jsonpath-old"] = OldJson()?.Path,
-                ["location-old"] = OldLocation(),
-                ["jsonref-new"] = NewJsonRef,
-                ["jsonpath-new"] = NewJson()?.Path,
-                ["location-new"] = NewLocation(),
-                ["type"] = Severity.ToString(),
-                ["docurl"] = DocUrl.ToString(),
-                ["mode"] = Mode.ToString()
+                id = Id.ToString(),
+                code = Code.ToString(),
+                message = Message,
+                type = Severity.ToString(),
+                docurl = DocUrl.ToString(),
+                mode = Mode.ToString(),
+                old = new JsonLocation
+                {
+                    @ref = OldJsonRef,
+                    path = OldJson()?.Path,
+                    location = OldLocation(),
+                },
+                @new = new JsonLocation
+                {
+                    @ref = NewJsonRef,
+                    path = NewJson()?.Path,
+                    location = NewLocation(),
+                }
             };
 
-            return JsonConvert.SerializeObject(rawMessage, Formatting.Indented);
+            return JsonConvert.SerializeObject(
+                rawMessage, 
+                Formatting.Indented,
+                new JsonSerializerSettings { NullValueHandling = NullValueHandling.Ignore }
+            );
         }
 
         public override string ToString()

openapi-diff/src/modeler/AutoRest.Swagger/JsonComparisonMessage.cs

@@ -0,0 +1,21 @@
+namespace AutoRest.Swagger
+{
+    sealed class JsonComparisonMessage
+    {
+        public string id;
+
+        public string code;
+
+        public string message;
+
+        public JsonLocation old;
+
+        public JsonLocation @new;
+
+        public string type;
+
+        public string docurl;
+
+        public string mode;
+    }
+}

openapi-diff/src/modeler/AutoRest.Swagger/JsonLocation.cs

@@ -0,0 +1,11 @@
+namespace AutoRest.Swagger
+{
+    sealed class JsonLocation
+    {
+        public string @ref;
+
+        public string path;
+
+        public string location;
+    }
+}