Fix escaping bug in MutableJsonDocument

sdk/core/Azure.Core.Experimental/src/MutableJsonDocument.cs

@@ -56,15 +56,15 @@ public void WriteTo(Stream stream, StandardFormat format = default)
                 throw new ArgumentOutOfRangeException(nameof(format));
             }
 
-            Utf8JsonWriter writer = new Utf8JsonWriter(stream);
             if (!Changes.HasChanges)
             {
                 Write(stream, _original.Span);
                 stream.Flush();
                 return;
             }
 
-            WriteRootElementTo(writer);
+            Utf8JsonWriter writer = new(stream);
+            RootElement.WriteTo(writer);
         }
 
         internal void WriteTo(Utf8JsonWriter writer)
@@ -75,7 +75,7 @@ internal void WriteTo(Utf8JsonWriter writer)
                 return;
             }
 
-            WriteRootElementTo(writer);
+            RootElement.WriteTo(writer);
         }
 
         private static void Write(Stream stream, ReadOnlySpan<byte> buffer)

sdk/core/Azure.Core.Experimental/src/MutableJsonElement.WriteTo.cs

@@ -0,0 +1,94 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+using System;
+using System.Text.Json;
+
+namespace Azure.Core.Json
+{
+    public partial struct MutableJsonElement
+    {
+        internal void WriteTo(Utf8JsonWriter writer)
+        {
+            WriteElement(_path, _highWaterMark, _element, writer);
+            writer.Flush();
+        }
+
+        private void WriteElement(string path, int highWaterMark, JsonElement originalElement, Utf8JsonWriter writer)
+        {
+            if (Changes.TryGetChange(path, highWaterMark, out MutableJsonChange change))
+            {
+                change.AsJsonElement().WriteTo(writer);
+                return;
+            }
+
+            if (Changes.DescendantChanged(path, highWaterMark))
+            {
+                switch (originalElement.ValueKind)
+                {
+                    case JsonValueKind.Object:
+                        WriteObject(path, highWaterMark, originalElement, writer);
+                        break;
+                    case JsonValueKind.Array:
+                        WriteArray(path, highWaterMark, originalElement, writer);
+                        break;
+                    default:
+                        throw new InvalidOperationException("Element doesn't have descendants.");
+                }
+
+                return;
+            }
+
+            originalElement.WriteTo(writer);
+        }
+
+        private void WriteObject(string path, int highWaterMark, JsonElement originalElement, Utf8JsonWriter writer)
+        {
+            writer.WriteStartObject();
+
+            foreach (JsonProperty property in originalElement.EnumerateObject())
+            {
+                string propertyPath = MutableJsonDocument.ChangeTracker.PushProperty(path, property.Name);
+
+                if (Changes.TryGetChange(propertyPath, highWaterMark, out MutableJsonChange change))
+                {
+                    writer.WritePropertyName(property.Name);
+                    change.AsJsonElement().WriteTo(writer);
+                    continue;
+                }
+
+                if (Changes.DescendantChanged(propertyPath, highWaterMark))
+                {
+                    writer.WritePropertyName(property.Name);
+                    WriteElement(propertyPath, highWaterMark, property.Value, writer);
+                    continue;
+                }
+
+                property.WriteTo(writer);
+            }
+
+            writer.WriteEndObject();
+        }
+
+        private void WriteArray(string path, int highWaterMark, JsonElement originalElement, Utf8JsonWriter writer)
+        {
+            if (Changes.TryGetChange(path, highWaterMark, out MutableJsonChange change))
+            {
+                JsonElement changedElement = change.AsJsonElement();
+                changedElement.WriteTo(writer);
+                return;
+            }
+
+            writer.WriteStartArray();
+
+            int arrayIndex = 0;
+            foreach (JsonElement arrayElement in originalElement.EnumerateArray())
+            {
+                string arrayElementPath = MutableJsonDocument.ChangeTracker.PushIndex(path, arrayIndex++);
+                WriteElement(arrayElementPath, highWaterMark, arrayElement, writer);
+            }
+
+            writer.WriteEndArray();
+        }
+    }
+}