Perf improvements for small or value-type POCOs

src/libraries/System.Text.Json/src/System.Text.Json.csproj

@@ -40,6 +40,7 @@
     <Compile Include="System\Text\Json\JsonException.cs" />
     <Compile Include="System\Text\Json\JsonHelpers.cs" />
     <Compile Include="System\Text\Json\JsonHelpers.Date.cs" />
+    <Compile Include="System\Text\Json\JsonHelpers.Escaping.cs" />
     <Compile Include="System\Text\Json\JsonTokenType.cs" />
     <Compile Include="System\Text\Json\Reader\ConsumeNumberResult.cs" />
     <Compile Include="System\Text\Json\Reader\ConsumeTokenResult.cs" />

src/libraries/System.Text.Json/src/System/Text/Json/JsonEncodedText.cs

@@ -32,15 +32,6 @@ private JsonEncodedText(byte[] utf8Value)
             _utf8Value = utf8Value;
         }
 
-        private JsonEncodedText(string stringValue, byte[] utf8Value)
-        {
-            Debug.Assert(stringValue != null);
-            Debug.Assert(utf8Value != null);
-
-            _value = stringValue;
-            _utf8Value = utf8Value;
-        }
-
         /// <summary>
         /// Encodes the string text value as a JSON string.
         /// </summary>
@@ -126,70 +117,14 @@ private static JsonEncodedText EncodeHelper(ReadOnlySpan<byte> utf8Value, JavaSc
 
             if (idx != -1)
             {
-                return new JsonEncodedText(GetEscapedString(utf8Value, idx, encoder));
+                return new JsonEncodedText(JsonHelpers.EscapeValue(utf8Value, idx, encoder));
             }
             else
             {
                 return new JsonEncodedText(utf8Value.ToArray());
             }
         }
 
-        /// <summary>
-        /// Internal version that keeps the existing string and byte[] references if there is no escaping required.
-        /// </summary>
-        internal static JsonEncodedText Encode(string stringValue, byte[] utf8Value, JavaScriptEncoder? encoder = null)
-        {
-            Debug.Assert(stringValue.Equals(JsonHelpers.Utf8GetString(utf8Value)));
-
-            if (utf8Value.Length == 0)
-            {
-                return new JsonEncodedText(stringValue, utf8Value);
-            }
-
-            JsonWriterHelper.ValidateValue(utf8Value);
-            return EncodeHelper(stringValue, utf8Value, encoder);
-        }
-
-        private static JsonEncodedText EncodeHelper(string stringValue, byte[] utf8Value, JavaScriptEncoder? encoder)
-        {
-            int idx = JsonWriterHelper.NeedsEscaping(utf8Value, encoder);
-
-            if (idx != -1)
-            {
-                return new JsonEncodedText(GetEscapedString(utf8Value, idx, encoder));
-            }
-            else
-            {
-                // Encoding is not necessary; use the same stringValue and utf8Value references.
-                return new JsonEncodedText(stringValue, utf8Value);
-            }
-        }
-
-        private static byte[] GetEscapedString(ReadOnlySpan<byte> utf8Value, int firstEscapeIndexVal, JavaScriptEncoder? encoder)
-        {
-            Debug.Assert(int.MaxValue / JsonConstants.MaxExpansionFactorWhileEscaping >= utf8Value.Length);
-            Debug.Assert(firstEscapeIndexVal >= 0 && firstEscapeIndexVal < utf8Value.Length);
-
-            byte[]? valueArray = null;
-
-            int length = JsonWriterHelper.GetMaxEscapedLength(utf8Value.Length, firstEscapeIndexVal);
-
-            Span<byte> escapedValue = length <= JsonConstants.StackallocThreshold ?
-                stackalloc byte[length] :
-                (valueArray = ArrayPool<byte>.Shared.Rent(length));
-
-            JsonWriterHelper.EscapeString(utf8Value, escapedValue, firstEscapeIndexVal, encoder, out int written);
-
-            byte[] escapedString = escapedValue.Slice(0, written).ToArray();
-
-            if (valueArray != null)
-            {
-                ArrayPool<byte>.Shared.Return(valueArray);
-            }
-
-            return escapedString;
-        }
-
         /// <summary>
         /// Determines whether this instance and another specified <see cref="JsonEncodedText"/> instance have the same value.
         /// </summary>

src/libraries/System.Text.Json/src/System/Text/Json/JsonHelpers.Escaping.cs

@@ -0,0 +1,98 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Buffers;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Text.Encodings.Web;
+
+namespace System.Text.Json
+{
+    internal static partial class JsonHelpers
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static byte[] GetEscapedPropertyNameSection(ReadOnlySpan<byte> utf8Value, JavaScriptEncoder? encoder)
+        {
+            int idx = JsonWriterHelper.NeedsEscaping(utf8Value, encoder);
+
+            if (idx != -1)
+            {
+                return GetEscapedPropertyNameSection(utf8Value, idx, encoder);
+            }
+            else
+            {
+                return GetPropertyNameSection(utf8Value);
+            }
+        }
+
+        public static byte[] EscapeValue(
+            ReadOnlySpan<byte> utf8Value,
+            int firstEscapeIndexVal,
+            JavaScriptEncoder? encoder)
+        {
+            Debug.Assert(int.MaxValue / JsonConstants.MaxExpansionFactorWhileEscaping >= utf8Value.Length);
+            Debug.Assert(firstEscapeIndexVal >= 0 && firstEscapeIndexVal < utf8Value.Length);
+
+            byte[]? valueArray = null;
+
+            int length = JsonWriterHelper.GetMaxEscapedLength(utf8Value.Length, firstEscapeIndexVal);
+
+            Span<byte> escapedValue = length <= JsonConstants.StackallocThreshold ?
+                stackalloc byte[length] :
+                (valueArray = ArrayPool<byte>.Shared.Rent(length));
+
+            JsonWriterHelper.EscapeString(utf8Value, escapedValue, firstEscapeIndexVal, encoder, out int written);
+
+            byte[] escapedString = escapedValue.Slice(0, written).ToArray();
+
+            if (valueArray != null)
+            {
+                ArrayPool<byte>.Shared.Return(valueArray);
+            }
+
+            return escapedString;
+        }
+
+        private static byte[] GetEscapedPropertyNameSection(
+            ReadOnlySpan<byte> utf8Value,
+            int firstEscapeIndexVal,
+            JavaScriptEncoder? encoder)
+        {
+            Debug.Assert(int.MaxValue / JsonConstants.MaxExpansionFactorWhileEscaping >= utf8Value.Length);
+            Debug.Assert(firstEscapeIndexVal >= 0 && firstEscapeIndexVal < utf8Value.Length);
+
+            byte[]? valueArray = null;
+
+            int length = JsonWriterHelper.GetMaxEscapedLength(utf8Value.Length, firstEscapeIndexVal);
+
+            Span<byte> escapedValue = length <= JsonConstants.StackallocThreshold ?
+                stackalloc byte[length] :
+                (valueArray = ArrayPool<byte>.Shared.Rent(length));
+
+            JsonWriterHelper.EscapeString(utf8Value, escapedValue, firstEscapeIndexVal, encoder, out int written);
+
+            byte[] propertySection = GetPropertyNameSection(escapedValue.Slice(0, written));
+
+            if (valueArray != null)
+            {
+                ArrayPool<byte>.Shared.Return(valueArray);
+            }
+
+            return propertySection;
+        }
+
+        private static byte[] GetPropertyNameSection(ReadOnlySpan<byte> utf8Value)
+        {
+            int length = utf8Value.Length;
+            byte[] propertySection = new byte[length + 3];
+
+            propertySection[0] = JsonConstants.Quote;
+            utf8Value.CopyTo(propertySection.AsSpan(1, length));
+            propertySection[++length] = JsonConstants.Quote;
+            propertySection[++length] = JsonConstants.KeyValueSeperator;
+
+            return propertySection;
+        }
+    }
+}

src/libraries/System.Text.Json/src/System/Text/Json/JsonHelpers.cs

@@ -91,7 +91,7 @@ public static void ReadWithVerify(this ref Utf8JsonReader reader)
         /// </summary>
         /// <param name="bytes">The utf8 bytes to convert.</param>
         /// <returns></returns>
-        internal static string Utf8GetString(ReadOnlySpan<byte> bytes)
+        public static string Utf8GetString(ReadOnlySpan<byte> bytes)
         {
             return Encoding.UTF8.GetString(bytes
 #if NETSTANDARD2_0 || NETFRAMEWORK
@@ -103,7 +103,7 @@ internal static string Utf8GetString(ReadOnlySpan<byte> bytes)
         /// <summary>
         /// Emulates Dictionary.TryAdd on netstandard.
         /// </summary>
-        internal static bool TryAdd<TKey, TValue>(Dictionary<TKey, TValue> dictionary, TKey key, TValue value) where TKey : notnull
+        public static bool TryAdd<TKey, TValue>(Dictionary<TKey, TValue> dictionary, in TKey key, in TValue value) where TKey : notnull
         {
 #if NETSTANDARD2_0 || NETFRAMEWORK
             if (!dictionary.ContainsKey(key))
@@ -118,7 +118,7 @@ internal static bool TryAdd<TKey, TValue>(Dictionary<TKey, TValue> dictionary, T
 #endif
         }
 
-        internal static bool IsFinite(double value)
+        public static bool IsFinite(double value)
         {
 #if BUILDING_INBOX_LIBRARY
             return double.IsFinite(value);
@@ -127,7 +127,7 @@ internal static bool IsFinite(double value)
 #endif
         }
 
-        internal static bool IsFinite(float value)
+        public static bool IsFinite(float value)
         {
 #if BUILDING_INBOX_LIBRARY
             return float.IsFinite(value);

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Collection/ArrayConverter.cs

@@ -16,7 +16,7 @@ internal sealed class ArrayConverter<TCollection, TElement>
     {
         internal override bool CanHaveIdMetadata => false;
 
-        protected override void Add(TElement value, ref ReadStack state)
+        protected override void Add(in TElement value, ref ReadStack state)
         {
             ((List<TElement>)state.Current.ReturnValue!).Add(value);
         }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Collection/ConcurrentQueueOfTConverter.cs

@@ -11,7 +11,7 @@ internal sealed class ConcurrentQueueOfTConverter<TCollection, TElement>
         : IEnumerableDefaultConverter<TCollection, TElement>
         where TCollection : ConcurrentQueue<TElement>
     {
-        protected override void Add(TElement value, ref ReadStack state)
+        protected override void Add(in TElement value, ref ReadStack state)
         {
             ((TCollection)state.Current.ReturnValue!).Enqueue(value);
         }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Collection/ConcurrentStackOfTConverter.cs

@@ -11,7 +11,7 @@ internal sealed class ConcurrentStackOfTConverter<TCollection, TElement>
         : IEnumerableDefaultConverter<TCollection, TElement>
         where TCollection : ConcurrentStack<TElement>
     {
-        protected override void Add(TElement value, ref ReadStack state)
+        protected override void Add(in TElement value, ref ReadStack state)
         {
             ((TCollection)state.Current.ReturnValue!).Push(value);
         }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Collection/DictionaryDefaultConverter.cs

@@ -16,7 +16,7 @@ internal abstract class DictionaryDefaultConverter<TCollection, TValue>
         /// <summary>
         /// When overridden, adds the value to the collection.
         /// </summary>
-        protected abstract void Add(TValue value, JsonSerializerOptions options, ref ReadStack state);
+        protected abstract void Add(in TValue value, JsonSerializerOptions options, ref ReadStack state);
 
         /// <summary>
         /// When overridden, converts the temporary collection held in state.Current.ReturnValue to the final collection.

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Collection/DictionaryOfStringTValueConverter.cs

@@ -14,7 +14,7 @@ internal sealed class DictionaryOfStringTValueConverter<TCollection, TValue>
         : DictionaryDefaultConverter<TCollection, TValue>
         where TCollection : Dictionary<string, TValue>
     {
-        protected override void Add(TValue value, JsonSerializerOptions options, ref ReadStack state)
+        protected override void Add(in TValue value, JsonSerializerOptions options, ref ReadStack state)
         {
             string key = state.Current.JsonPropertyNameAsString!;
             ((TCollection)state.Current.ReturnValue!)[key] = value;

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Collection/ICollectionOfTConverter.cs

@@ -13,7 +13,7 @@ internal sealed class ICollectionOfTConverter<TCollection, TElement>
         : IEnumerableDefaultConverter<TCollection, TElement>
         where TCollection : ICollection<TElement>
     {
-        protected override void Add(TElement value, ref ReadStack state)
+        protected override void Add(in TElement value, ref ReadStack state)
         {
             ((ICollection<TElement>)state.Current.ReturnValue!).Add(value);
         }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Collection/IDictionaryConverter.cs

@@ -15,7 +15,7 @@ internal sealed class IDictionaryConverter<TCollection>
         : DictionaryDefaultConverter<TCollection, object?>
         where TCollection : IDictionary
     {
-        protected override void Add(object? value, JsonSerializerOptions options, ref ReadStack state)
+        protected override void Add(in object? value, JsonSerializerOptions options, ref ReadStack state)
         {
             string key = state.Current.JsonPropertyNameAsString!;
             ((IDictionary)state.Current.ReturnValue!)[key] = value;

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Collection/IDictionaryOfStringTValueConverter.cs

@@ -14,7 +14,7 @@ internal sealed class IDictionaryOfStringTValueConverter<TCollection, TValue>
         : DictionaryDefaultConverter<TCollection, TValue>
         where TCollection : IDictionary<string, TValue>
     {
-        protected override void Add(TValue value, JsonSerializerOptions options, ref ReadStack state)
+        protected override void Add(in TValue value, JsonSerializerOptions options, ref ReadStack state)
         {
             string key = state.Current.JsonPropertyNameAsString!;
             ((TCollection)state.Current.ReturnValue!)[key] = value;

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Collection/IEnumerableConverter.cs

@@ -15,7 +15,7 @@ internal sealed class IEnumerableConverter<TCollection>
         : IEnumerableDefaultConverter<TCollection, object?>
         where TCollection : IEnumerable
     {
-        protected override void Add(object? value, ref ReadStack state)
+        protected override void Add(in object? value, ref ReadStack state)
         {
             ((List<object?>)state.Current.ReturnValue!).Add(value);
         }
@@ -62,7 +62,8 @@ protected override bool OnWriteResume(
                     return false;
                 }
 
-                if (!converter.TryWrite(writer, enumerator.Current, options, ref state))
+                object? element = enumerator.Current;
+                if (!converter.TryWrite(writer, element, options, ref state))
                 {
                     state.Current.CollectionEnumerator = enumerator;
                     return false;

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Collection/IEnumerableConverterFactoryHelpers.cs

@@ -46,7 +46,7 @@ internal static class IEnumerableConverterFactoryHelpers
 
             Type? baseTypeToCheck = type;
 
-            while (baseTypeToCheck != null && baseTypeToCheck != typeof(object))
+            while (baseTypeToCheck != null && baseTypeToCheck != JsonClassInfo.ObjectType)
             {
                 if (baseTypeToCheck.IsGenericType)
                 {

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Collection/IEnumerableDefaultConverter.cs

@@ -13,7 +13,7 @@ namespace System.Text.Json.Serialization.Converters
     internal abstract class IEnumerableDefaultConverter<TCollection, TElement>
         : JsonCollectionConverter<TCollection, TElement>
     {
-        protected abstract void Add(TElement value, ref ReadStack state);
+        protected abstract void Add(in TElement value, ref ReadStack state);
         protected abstract void CreateCollection(ref Utf8JsonReader reader, ref ReadStack state, JsonSerializerOptions options);
         protected virtual void ConvertCollection(ref ReadStack state, JsonSerializerOptions options) { }
 
@@ -242,7 +242,11 @@ internal override bool OnTryRead(
             return true;
         }
 
-        internal sealed override bool OnTryWrite(Utf8JsonWriter writer, TCollection value, JsonSerializerOptions options, ref WriteStack state)
+        internal sealed override bool OnTryWrite(
+            Utf8JsonWriter writer,
+            TCollection value,
+            JsonSerializerOptions options,
+            ref WriteStack state)
         {
             bool success;
 

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Collection/IEnumerableOfTConverter.cs

@@ -14,7 +14,7 @@ internal sealed class IEnumerableOfTConverter<TCollection, TElement>
         : IEnumerableDefaultConverter<TCollection, TElement>
         where TCollection : IEnumerable<TElement>
     {
-        protected override void Add(TElement value, ref ReadStack state)
+        protected override void Add(in TElement value, ref ReadStack state)
         {
             ((List<TElement>)state.Current.ReturnValue!).Add(value);
         }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Collection/IEnumerableWithAddMethodConverter.cs

@@ -10,7 +10,7 @@ internal sealed class IEnumerableWithAddMethodConverter<TCollection>
         : IEnumerableDefaultConverter<TCollection, object?>
         where TCollection : IEnumerable
     {
-        protected override void Add(object? value, ref ReadStack state)
+        protected override void Add(in object? value, ref ReadStack state)
         {
             ((Action<TCollection, object?>)state.Current.AddMethodDelegate!)((TCollection)state.Current.ReturnValue!, value);
         }
@@ -53,7 +53,8 @@ protected override bool OnWriteResume(Utf8JsonWriter writer, TCollection value,
                     return false;
                 }
 
-                if (!converter.TryWrite(writer, enumerator.Current, options, ref state))
+                object? element = enumerator.Current;
+                if (!converter.TryWrite(writer, element, options, ref state))
                 {
                     state.Current.CollectionEnumerator = enumerator;
                     return false;

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Collection/IListConverter.cs

@@ -12,7 +12,7 @@ internal sealed class IListConverter<TCollection>
         : IEnumerableDefaultConverter<TCollection, object?>
         where TCollection : IList
     {
-        protected override void Add(object? value, ref ReadStack state)
+        protected override void Add(in object? value, ref ReadStack state)
         {
             ((IList)state.Current.ReturnValue!).Add(value);
         }
@@ -74,7 +74,6 @@ protected override bool OnWriteResume(Utf8JsonWriter writer, TCollection value,
                 }
 
                 object? element = enumerator.Current;
-
                 if (!converter.TryWrite(writer, element, options, ref state))
                 {
                     state.Current.CollectionEnumerator = enumerator;