Applying feedback

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

@@ -598,7 +598,7 @@ public void Skip() { }
         public bool TrySkip() { throw null; }
         public bool ValueTextEquals(System.ReadOnlySpan<byte> utf8Text) { throw null; }
         public bool ValueTextEquals(System.ReadOnlySpan<char> text) { throw null; }
-        public bool ValueTextEquals(string text) { throw null; }
+        public bool ValueTextEquals(string? text) { throw null; }
     }
     public sealed partial class Utf8JsonWriter : System.IAsyncDisposable, System.IDisposable
     {

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

@@ -14,7 +14,7 @@ namespace System.Text.Json
     public class JsonException : Exception
     {
         // Allow the message to mutate to avoid re-throwing and losing the StackTrace to an inner exception.
-        private string? _message;
+        internal string? _message;
 
         /// <summary>
         /// Creates a new exception object to relay error information to the user.
@@ -134,7 +134,7 @@ public override string Message
         {
             get
             {
-                return _message!;
+                return _message ?? base.Message;
             }
         }
 

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

@@ -36,7 +36,15 @@ private protected JsonNode() { }
         /// <exception cref="ArgumentException">
         ///   Provided <see cref="JsonElement"/> was not built from <see cref="JsonNode"/>.
         /// </exception>
-        public static JsonNode GetNode(JsonElement jsonElement) => !jsonElement.IsImmutable ? (JsonNode)jsonElement._parent! : throw new ArgumentException(SR.NotNodeJsonElementParent);
+        public static JsonNode GetNode(JsonElement jsonElement)
+        {
+            if (jsonElement.IsImmutable)
+            {
+                throw new ArgumentException(SR.NotNodeJsonElementParent);
+            }
+            Debug.Assert(jsonElement._parent != null);
+            return (JsonNode)jsonElement._parent;
+        }
 
         /// <summary>
         ///    Gets the <see cref="JsonNode"/> represented by the <paramref name="jsonElement"/>.

src/libraries/System.Text.Json/src/System/Text/Json/Reader/JsonReaderException.cs

@@ -10,7 +10,7 @@ namespace System.Text.Json
     [Serializable]
     internal sealed class JsonReaderException : JsonException
     {
-        public JsonReaderException(string? message, long lineNumber, long bytePositionInLine) : base(message, path: null, lineNumber, bytePositionInLine)
+        public JsonReaderException(string message, long lineNumber, long bytePositionInLine) : base(message, path: null, lineNumber, bytePositionInLine)
         {
         }
 

src/libraries/System.Text.Json/src/System/Text/Json/Reader/Utf8JsonReader.cs

@@ -458,7 +458,7 @@ public bool ValueTextEquals(ReadOnlySpan<byte> utf8Text)
         ///     if required. The look up text is matched as is, without any modifications to it.
         ///   </para>
         /// </remarks>
-        public bool ValueTextEquals(string text)
+        public bool ValueTextEquals(string? text)
         {
             return ValueTextEquals(text.AsSpan());
         }

src/libraries/System.Text.Json/src/System/Text/Json/ThrowHelper.Serialization.cs

@@ -141,7 +141,7 @@ public static void ThrowInvalidOperationException_SerializerDictionaryKeyNull(Ty
         [MethodImpl(MethodImplOptions.NoInlining)]
         public static void ReThrowWithPath(in ReadStack readStack, JsonReaderException ex)
         {
-            Debug.Assert(ex.Path == null && ex.Message != null);
+            Debug.Assert(ex.Path == null);
 
             string path = readStack.JsonPath();
             string message = ex.Message;
@@ -179,7 +179,7 @@ public static void AddExceptionInformation(in ReadStack readStack, in Utf8JsonRe
             string path = readStack.JsonPath();
             ex.Path = path;
 
-            string? message = ex.Message;
+            string? message = ex._message;
 
             if (string.IsNullOrEmpty(message))
             {
@@ -214,7 +214,7 @@ public static void AddExceptionInformation(in WriteStack writeStack, JsonExcepti
             string path = writeStack.PropertyPath();
             ex.Path = path;
 
-            string? message = ex.Message;
+            string? message = ex._message;
             if (string.IsNullOrEmpty(message))
             {
                 // Use a default message.