Performance improvements in JsonValue.

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

@@ -75,6 +75,7 @@ The System.Text.Json library is built-in as part of the shared framework in .NET
     <Compile Include="System\Text\Json\JsonTokenType.cs" />
     <Compile Include="System\Text\Json\Nodes\JsonArray.cs" />
     <Compile Include="System\Text\Json\Nodes\JsonArray.IList.cs" />
+    <Compile Include="System\Text\Json\Nodes\JsonValueOfElement.cs" />
     <Compile Include="System\Text\Json\Nodes\JsonNode.cs" />
     <Compile Include="System\Text\Json\Nodes\JsonNode.Operators.cs" />
     <Compile Include="System\Text\Json\Nodes\JsonNode.Parse.cs" />
@@ -380,12 +381,6 @@ The System.Text.Json library is built-in as part of the shared framework in .NET
     <Compile Include="System\Text\Json\Reader\JsonReaderHelper.netstandard.cs" />
   </ItemGroup>
 
-  <ItemGroup>
-    <None Include="System\Text\Json\OrderedDictionary.cs" />
-    <None Include="System\Text\Json\OrderedDictionary.KeyCollection.cs" />
-    <None Include="System\Text\Json\OrderedDictionary.ValueCollection.cs" />
-  </ItemGroup>
-
   <!-- Application tfms (.NETCoreApp, .NETFramework) need to use the same or higher version of .NETStandard's dependencies. -->
   <ItemGroup>
     <ProjectReference Include="$(LibrariesProjectRoot)System.Text.Encodings.Web\src\System.Text.Encodings.Web.csproj" />

src/libraries/System.Text.Json/src/System/Text/Json/Document/JsonDocument.cs

@@ -118,6 +118,17 @@ internal JsonTokenType GetJsonTokenType(int index)
             return _parsedData.GetJsonTokenType(index);
         }
 
+        internal bool ValueIsEscaped(int index, bool isPropertyName)
+        {
+            CheckNotDisposed();
+
+            int matchIndex = isPropertyName ? index - DbRow.Size : index;
+            DbRow row = _parsedData.Get(matchIndex);
+            Debug.Assert(!isPropertyName || row.TokenType is JsonTokenType.PropertyName);
+
+            return row.HasComplexChildren;
+        }
+
         internal int GetArrayLength(int index)
         {
             CheckNotDisposed();
@@ -363,6 +374,16 @@ internal string GetNameOfPropertyValue(int index)
             return GetString(index - DbRow.Size, JsonTokenType.PropertyName)!;
         }
 
+        internal ReadOnlySpan<byte> GetPropertyNameRaw(int index)
+        {
+            CheckNotDisposed();
+
+            DbRow row = _parsedData.Get(index - DbRow.Size);
+            Debug.Assert(row.TokenType is JsonTokenType.PropertyName);
+
+            return _utf8Json.Span.Slice(row.Location, row.SizeOrLength);
+        }
+
         internal bool TryGetValue(int index, [NotNullWhen(true)] out byte[]? value)
         {
             CheckNotDisposed();

src/libraries/System.Text.Json/src/System/Text/Json/Document/JsonElement.cs

@@ -1164,6 +1164,13 @@ internal string GetPropertyName()
             return _parent.GetNameOfPropertyValue(_idx);
         }
 
+        internal ReadOnlySpan<byte> GetPropertyNameRaw()
+        {
+            CheckValidInstance();
+
+            return _parent.GetPropertyNameRaw(_idx);
+        }
+
         /// <summary>
         ///   Gets the original input data backing this value, returning it as a <see cref="string"/>.
         /// </summary>
@@ -1194,6 +1201,154 @@ internal string GetPropertyRawText()
             return _parent.GetPropertyRawValueAsString(_idx);
         }
 
+        internal bool ValueIsEscaped
+        {
+            // TODO make public https://github.com/dotnet/runtime/issues/77666
+            get
+            {
+                CheckValidInstance();
+
+                return _parent.ValueIsEscaped(_idx, isPropertyName: false);
+            }
+        }
+
+        internal ReadOnlySpan<byte> ValueSpan
+        {
+            // TODO make public https://github.com/dotnet/runtime/issues/77666
+            get
+            {
+                CheckValidInstance();
+
+                return _parent.GetRawValue(_idx, includeQuotes: false).Span;
+            }
+        }
+
+        // TODO make public https://github.com/dotnet/runtime/issues/33388
+        internal static bool DeepEquals(JsonElement left, JsonElement right)
+        {
+            Debug.Assert(left._parent != null);
+            Debug.Assert(right._parent != null);
+
+            JsonValueKind kind = left.ValueKind;
+            if (kind != right.ValueKind)
+            {
+                return false;
+            }
+
+            switch (kind)
+            {
+                case JsonValueKind.Null or JsonValueKind.False or JsonValueKind.True:
+                    return true;
+
+                case JsonValueKind.Number:
+                    // JSON numbers are equal if their raw representations are equal.
+                    return left.GetRawValue().Span.SequenceEqual(right.GetRawValue().Span);
+
+                case JsonValueKind.String:
+                    if (right.ValueIsEscaped)
+                    {
+                        if (left.ValueIsEscaped)
+                        {
+                            // Both values are escaped, force an allocation to unescape the RHS.
+                            return left.ValueEquals(right.GetString());
+                        }
+
+                        // Swap values so that unescaping is handled by the LHS.
+                        (left, right) = (right, left);
+                    }
+
+                    return left.ValueEquals(right.ValueSpan);
+
+                case JsonValueKind.Array:
+                    ArrayEnumerator rightArrayEnumerator = right.EnumerateArray();
+                    foreach (JsonElement leftElement in left.EnumerateArray())
+                    {
+                        if (!rightArrayEnumerator.MoveNext() || !DeepEquals(leftElement, rightArrayEnumerator.Current))
+                        {
+                            return false;
+                        }
+                    }
+
+                    return !rightArrayEnumerator.MoveNext();
+
+                default:
+                    Debug.Assert(kind is JsonValueKind.Object);
+                    ObjectEnumerator leftObjectEnumerator = left.EnumerateObject();
+                    ObjectEnumerator rightObjectEnumerator = right.EnumerateObject();
+
+                    // Two JSON objects are considered equal if they define the same set of properties.
+                    // Start optimistically with sequential comparison, but fall back to unordered
+                    // comparison as soon as a mismatch is encountered.
+
+                    while (leftObjectEnumerator.MoveNext())
+                    {
+                        if (!rightObjectEnumerator.MoveNext())
+                        {
+                            return false;
+                        }
+
+                        JsonProperty leftProp = leftObjectEnumerator.Current;
+                        JsonProperty rightProp = rightObjectEnumerator.Current;
+
+                        if (!NameEquals(leftProp, rightProp))
+                        {
+                            // We have our first mismatch, fall back to unordered comparison.
+                            return UnorderedObjectDeepEquals(leftObjectEnumerator, rightObjectEnumerator);
+                        }
+
+                        if (!DeepEquals(leftProp.Value, rightProp.Value))
+                        {
+                            return false;
+                        }
+                    }
+
+                    return !rightObjectEnumerator.MoveNext();
+
+                    static bool UnorderedObjectDeepEquals(ObjectEnumerator left, ObjectEnumerator right)
+                    {
+                        Dictionary<string, JsonElement> rightElements = new(StringComparer.Ordinal);
+                        do
+                        {
+                            JsonProperty prop = right.Current;
+                            rightElements.TryAdd(prop.Name, prop.Value);
+                        }
+                        while (right.MoveNext());
+
+                        int leftCount = 0;
+                        do
+                        {
+                            JsonProperty prop = left.Current;
+                            if (!rightElements.TryGetValue(prop.Name, out JsonElement rightElement) || !DeepEquals(prop.Value, rightElement))
+                            {
+                                return false;
+                            }
+
+                            leftCount++;
+                        }
+                        while (left.MoveNext());
+
+                        return leftCount == rightElements.Count;
+                    }
+
+                    static bool NameEquals(JsonProperty left, JsonProperty right)
+                    {
+                        if (right.NameIsEscaped)
+                        {
+                            if (left.NameIsEscaped)
+                            {
+                                // Both values are escaped, force an allocation to unescape the RHS.
+                                return left.NameEquals(right.Name);
+                            }
+
+                            // Swap values so that unescaping is handled by the LHS
+                            (left, right) = (right, left);
+                        }
+
+                        return left.NameEquals(right.NameSpan);
+                    }
+            }
+        }
+
         /// <summary>
         ///   Compares <paramref name="text" /> to the string value of this element.
         /// </summary>
@@ -1292,6 +1447,13 @@ internal bool TextEqualsHelper(ReadOnlySpan<char> text, bool isPropertyName)
             return _parent.TextEquals(_idx, text, isPropertyName);
         }
 
+        internal bool ValueIsEscapedHelper(bool isPropertyName)
+        {
+            CheckValidInstance();
+
+            return _parent.ValueIsEscaped(_idx, isPropertyName);
+        }
+
         /// <summary>
         ///   Write the element into the provided writer as a JSON value.
         /// </summary>

src/libraries/System.Text.Json/src/System/Text/Json/Document/JsonProperty.cs

@@ -18,10 +18,9 @@ public readonly struct JsonProperty
         public JsonElement Value { get; }
         private string? _name { get; }
 
-        internal JsonProperty(JsonElement value, string? name = null)
+        internal JsonProperty(JsonElement value)
         {
             Value = value;
-            _name = name;
         }
 
         /// <summary>
@@ -94,6 +93,10 @@ internal bool EscapedNameEquals(ReadOnlySpan<byte> utf8Text)
             return Value.TextEqualsHelper(utf8Text, isPropertyName: true, shouldUnescape: false);
         }
 
+        // TODO make public https://github.com/dotnet/runtime/issues/77666
+        internal bool NameIsEscaped => Value.ValueIsEscapedHelper(isPropertyName: true);
+        internal ReadOnlySpan<byte> NameSpan => Value.GetPropertyNameRaw();
+
         /// <summary>
         ///   Write the property into the provided writer as a named JSON object property.
         /// </summary>

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

@@ -23,6 +23,8 @@ public sealed partial class JsonArray : JsonNode
         private JsonElement? _jsonElement;
         private List<JsonNode?>? _list;
 
+        internal override JsonElement? UnderlyingElement => _jsonElement;
+
         /// <summary>
         ///   Initializes a new instance of the <see cref="JsonArray"/> class that is empty.
         /// </summary>
@@ -93,11 +95,11 @@ internal override JsonNode DeepCloneCore()
             return jsonArray;
         }
 
-        internal override bool DeepEqualsCore(JsonNode? node)
+        internal override bool DeepEqualsCore(JsonNode node)
         {
             switch (node)
             {
-                case null or JsonObject:
+                case JsonObject:
                     return false;
                 case JsonValue value:
                     // JsonValue instances have special comparison semantics, dispatch to their implementation.

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

@@ -44,13 +44,12 @@ public override string ToString()
             // Special case for string; don't quote it.
             if (this is JsonValue)
             {
-                if (this is JsonValue<string> jsonString)
+                if (this is JsonValuePrimitive<string> jsonString)
                 {
                     return jsonString.Value;
                 }
 
-                if (this is JsonValue<JsonElement> jsonElement &&
-                    jsonElement.Value.ValueKind == JsonValueKind.String)
+                if (this is JsonValueOfElement { Value.ValueKind: JsonValueKind.String } jsonElement)
                 {
                     return jsonElement.Value.GetString()!;
                 }

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

@@ -14,9 +14,17 @@ namespace System.Text.Json.Nodes
     /// declared as an <see cref="object"/> should be deserialized as a <see cref="JsonNode"/>.
     public abstract partial class JsonNode
     {
+        // Default options instance used when calling built-in JsonNode converters.
+        private protected static readonly JsonSerializerOptions s_defaultOptions = new();
+
         private JsonNode? _parent;
         private JsonNodeOptions? _options;
 
+        /// <summary>
+        /// The underlying JsonElement if the node is backed by a JsonElement.
+        /// </summary>
+        internal virtual JsonElement? UnderlyingElement => null;
+
         /// <summary>
         ///   Options to control the behavior.
         /// </summary>
@@ -300,11 +308,15 @@ public static bool DeepEquals(JsonNode? node1, JsonNode? node2)
             {
                 return node2 is null;
             }
+            else if (node2 is null)
+            {
+                return false;
+            }
 
             return node1.DeepEqualsCore(node2);
         }
 
-        internal abstract bool DeepEqualsCore(JsonNode? node);
+        internal abstract bool DeepEqualsCore(JsonNode node);
 
         /// <summary>
         /// Replaces this node with a new value.
@@ -375,7 +387,7 @@ internal void AssignParent(JsonNode parent)
             }
 
             var jsonTypeInfo = (JsonTypeInfo<T>)JsonSerializerOptions.Default.GetTypeInfo(typeof(T));
-            return new JsonValueCustomized<T>(value, jsonTypeInfo, options);
+            return JsonValue.CreateFromTypeInfo(value, jsonTypeInfo, options);
         }
     }
 }

src/libraries/System.Text.Json/src/System/Text/Json/Nodes/JsonObject.IDictionary.cs

@@ -25,6 +25,11 @@ public partial class JsonObject : IDictionary<string, JsonNode?>
         /// </exception>
         public void Add(string propertyName, JsonNode? value)
         {
+            if (propertyName is null)
+            {
+                ThrowHelper.ThrowArgumentNullException(nameof(propertyName));
+            }
+
             Dictionary.Add(propertyName, value);
             value?.AssignParent(this);
         }
@@ -74,7 +79,15 @@ public void Clear()
         /// <exception cref="ArgumentNullException">
         ///   <paramref name="propertyName"/> is <see langword="null"/>.
         /// </exception>
-        public bool ContainsKey(string propertyName) => Dictionary.ContainsKey(propertyName);
+        public bool ContainsKey(string propertyName)
+        {
+            if (propertyName is null)
+            {
+                ThrowHelper.ThrowArgumentNullException(nameof(propertyName));
+            }
+
+            return Dictionary.ContainsKey(propertyName);
+        }
 
         /// <summary>
         ///   Gets the number of elements contained in <see cref="JsonObject"/>.
@@ -180,7 +193,15 @@ public bool Remove(string propertyName)
         /// <exception cref="ArgumentNullException">
         ///   <paramref name="propertyName"/> is <see langword="null"/>.
         /// </exception>
-        bool IDictionary<string, JsonNode?>.TryGetValue(string propertyName, out JsonNode? jsonNode) => Dictionary.TryGetValue(propertyName, out jsonNode);
+        bool IDictionary<string, JsonNode?>.TryGetValue(string propertyName, out JsonNode? jsonNode)
+        {
+            if (propertyName is null)
+            {
+                ThrowHelper.ThrowArgumentNullException(nameof(propertyName));
+            }
+
+            return Dictionary.TryGetValue(propertyName, out jsonNode);
+        }
 
         /// <summary>
         ///   Returns <see langword="false"/>.