Use Utf8JsonWriterCache in JsonNode.To{Json}String

src/libraries/System.Text.Json/src/System/Text/Json/Nodes/JsonNode.To.cs

@@ -1,6 +1,8 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Threading;
+
 namespace System.Text.Json.Nodes
 {
     public abstract partial class JsonNode
@@ -12,8 +14,25 @@ public abstract partial class JsonNode
         /// <returns>JSON representation of current instance.</returns>
         public string ToJsonString(JsonSerializerOptions? options = null)
         {
-            using PooledByteBufferWriter output = WriteToPooledBuffer(options, options?.GetWriterOptions() ?? default);
-            return JsonHelpers.Utf8GetString(output.WrittenMemory.Span);
+            JsonWriterOptions writerOptions = default;
+            int defaultBufferSize = JsonSerializerOptions.BufferSizeDefault;
+            if (options is not null)
+            {
+                writerOptions = options.GetWriterOptions();
+                defaultBufferSize = options.DefaultBufferSize;
+            }
+
+            Utf8JsonWriter writer = Utf8JsonWriterCache.RentWriterAndBuffer(writerOptions, defaultBufferSize, out PooledByteBufferWriter output);
+            try
+            {
+                WriteTo(writer, options);
+                writer.Flush();
+                return JsonHelpers.Utf8GetString(output.WrittenMemory.Span);
+            }
+            finally
+            {
+                Utf8JsonWriterCache.ReturnWriterAndBuffer(writer, output);
+            }
         }
 
         /// <summary>
@@ -37,8 +56,17 @@ public override string ToString()
                 }
             }
 
-            using PooledByteBufferWriter output = WriteToPooledBuffer(writerOptions: new JsonWriterOptions { Indented = true });
-            return JsonHelpers.Utf8GetString(output.WrittenMemory.Span);
+            Utf8JsonWriter writer = Utf8JsonWriterCache.RentWriterAndBuffer(new JsonWriterOptions { Indented = true }, JsonSerializerOptions.BufferSizeDefault, out PooledByteBufferWriter output);
+            try
+            {
+                WriteTo(writer);
+                writer.Flush();
+                return JsonHelpers.Utf8GetString(output.WrittenMemory.Span);
+            }
+            finally
+            {
+                Utf8JsonWriterCache.ReturnWriterAndBuffer(writer, output);
+            }
         }
 
         /// <summary>
@@ -50,19 +78,5 @@ public override string ToString()
         /// </exception>
         /// <param name="options">Options to control the serialization behavior.</param>
         public abstract void WriteTo(Utf8JsonWriter writer, JsonSerializerOptions? options = null);
-
-        /// <summary>
-        /// Creates a pooled buffer writer instance and serializes all contents to it.
-        /// </summary>
-        internal PooledByteBufferWriter WriteToPooledBuffer(
-            JsonSerializerOptions? options = null,
-            JsonWriterOptions writerOptions = default,
-            int bufferSize = JsonSerializerOptions.BufferSizeDefault)
-        {
-            var bufferWriter = new PooledByteBufferWriter(bufferSize);
-            using var writer = new Utf8JsonWriter(bufferWriter, writerOptions);
-            WriteTo(writer, options);
-            return bufferWriter;
-        }
     }
 }

src/libraries/System.Text.Json/src/System/Text/Json/Nodes/JsonValueOfT.cs

@@ -72,8 +72,17 @@ internal sealed override JsonValueKind GetValueKindCore()
                 return element.ValueKind;
             }
 
-            using PooledByteBufferWriter output = WriteToPooledBuffer();
-            return JsonElement.ParseValue(output.WrittenMemory.Span, options: default).ValueKind;
+            Utf8JsonWriter writer = Utf8JsonWriterCache.RentWriterAndBuffer(default, JsonSerializerOptions.BufferSizeDefault, out PooledByteBufferWriter output);
+            try
+            {
+                WriteTo(writer);
+                writer.Flush();
+                return JsonElement.ParseValue(output.WrittenMemory.Span, options: default).ValueKind;
+            }
+            finally
+            {
+                Utf8JsonWriterCache.ReturnWriterAndBuffer(writer, output);
+            }
         }
 
         internal sealed override bool DeepEqualsCore(JsonNode? otherNode)
@@ -107,9 +116,21 @@ internal sealed override bool DeepEqualsCore(JsonNode? otherNode)
                 }
             }
 
-            using PooledByteBufferWriter thisOutput = WriteToPooledBuffer();
-            using PooledByteBufferWriter otherOutput = otherNode.WriteToPooledBuffer();
+            using PooledByteBufferWriter thisOutput = WriteToPooledBuffer(this);
+            using PooledByteBufferWriter otherOutput = WriteToPooledBuffer(otherNode);
             return thisOutput.WrittenMemory.Span.SequenceEqual(otherOutput.WrittenMemory.Span);
+
+            static PooledByteBufferWriter WriteToPooledBuffer(
+                JsonNode node,
+                JsonSerializerOptions? options = null,
+                JsonWriterOptions writerOptions = default,
+                int bufferSize = JsonSerializerOptions.BufferSizeDefault)
+            {
+                var bufferWriter = new PooledByteBufferWriter(bufferSize);
+                using var writer = new Utf8JsonWriter(bufferWriter, writerOptions);
+                node.WriteTo(writer, options);
+                return bufferWriter;
+            }
         }
 
         internal TypeToConvert ConvertJsonElement<TypeToConvert>()

src/libraries/System.Text.Json/src/System/Text/Json/Writer/Utf8JsonWriterCache.cs

@@ -13,7 +13,10 @@ internal static class Utf8JsonWriterCache
         [ThreadStatic]
         private static ThreadLocalState? t_threadLocalState;
 
-        public static Utf8JsonWriter RentWriterAndBuffer(JsonSerializerOptions options, out PooledByteBufferWriter bufferWriter)
+        public static Utf8JsonWriter RentWriterAndBuffer(JsonSerializerOptions options, out PooledByteBufferWriter bufferWriter) =>
+            RentWriterAndBuffer(options.GetWriterOptions(), options.DefaultBufferSize, out bufferWriter);
+
+        public static Utf8JsonWriter RentWriterAndBuffer(JsonWriterOptions options, int defaultBufferSize, out PooledByteBufferWriter bufferWriter)
         {
             ThreadLocalState state = t_threadLocalState ??= new();
             Utf8JsonWriter writer;
@@ -24,14 +27,14 @@ public static Utf8JsonWriter RentWriterAndBuffer(JsonSerializerOptions options,
                 bufferWriter = state.BufferWriter;
                 writer = state.Writer;
 
-                bufferWriter.InitializeEmptyInstance(options.DefaultBufferSize);
-                writer.Reset(bufferWriter, options.GetWriterOptions());
+                bufferWriter.InitializeEmptyInstance(defaultBufferSize);
+                writer.Reset(bufferWriter, options);
             }
             else
             {
                 // We're in a recursive JsonSerializer call -- return fresh instances.
-                bufferWriter = new PooledByteBufferWriter(options.DefaultBufferSize);
-                writer = new Utf8JsonWriter(bufferWriter, options.GetWriterOptions());
+                bufferWriter = new PooledByteBufferWriter(defaultBufferSize);
+                writer = new Utf8JsonWriter(bufferWriter, options);
             }
 
             return writer;