Implement WriteStringValueSegment defined in Issue 67337

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

@@ -426,6 +426,7 @@ public enum JsonTokenType : byte
         True = (byte)9,
         False = (byte)10,
         Null = (byte)11,
+        StringSegment = (byte)12,
     }
     public enum JsonValueKind : byte
     {
@@ -652,6 +653,10 @@ public void WriteStringValue(System.ReadOnlySpan<byte> utf8Value) { }
         public void WriteStringValue(System.ReadOnlySpan<char> value) { }
         public void WriteStringValue(string? value) { }
         public void WriteStringValue(System.Text.Json.JsonEncodedText value) { }
+        public void WriteStringValueSegment(System.ReadOnlySpan<byte> utf8Value, bool isFinalSegment) { }
+        public void WriteStringValueSegment(ReadOnlySpan<char> value, bool isFinalSegment) { }
+        public void WriteStringValueSegment(string? value, bool isFinalSegment) { }
+        public void WriteStringValueSegment(System.Text.Json.JsonEncodedText value, bool isFinalSegment) { }
     }
 }
 namespace System.Text.Json.Nodes

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

@@ -77,5 +77,14 @@ public enum JsonTokenType : byte
         ///   Indicates that the token type is the JSON literal <c>null</c>.
         /// </summary>
         Null,
+
+        /// <summary>
+        ///   Indicates that the token type is a segment of a JSON string.
+        /// </summary>
+        /// <remarks>
+        ///   This does not represent a token defined in the JSON specification, but rather provides a means to track
+        ///   that a string is being written in segments. This value will never be seen during deserialization.
+        /// </remarks>
+        StringSegment,
     }
 }

src/libraries/System.Text.Json/src/System/Text/Json/Writer/Utf8JsonWriter.WriteProperties.Helpers.cs

@@ -36,7 +36,7 @@ private void ValidateWritingProperty()
         {
             if (!_options.SkipValidation)
             {
-                if (!_inObject || _tokenType == JsonTokenType.PropertyName)
+                if (!_inObject || _tokenType == JsonTokenType.PropertyName || _tokenType == JsonTokenType.StringSegment)
                 {
                     Debug.Assert(_tokenType != JsonTokenType.StartObject);
                     ThrowHelper.ThrowInvalidOperationException(ExceptionResource.CannotWritePropertyWithinArray, currentDepth: default, maxDepth: _options.MaxDepth, token: default, _tokenType);
@@ -49,7 +49,7 @@ private void ValidateWritingProperty(byte token)
         {
             if (!_options.SkipValidation)
             {
-                if (!_inObject || _tokenType == JsonTokenType.PropertyName)
+                if (!_inObject || _tokenType == JsonTokenType.PropertyName || _tokenType == JsonTokenType.StringSegment)
                 {
                     Debug.Assert(_tokenType != JsonTokenType.StartObject);
                     ThrowHelper.ThrowInvalidOperationException(ExceptionResource.CannotWritePropertyWithinArray, currentDepth: default, maxDepth: _options.MaxDepth, token: default, _tokenType);