Add JsonConverter.Write/ReadAsPropertyName APIs

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

@@ -818,12 +818,14 @@ protected internal JsonConverter() { }
         public virtual bool HandleNull { get { throw null; } }
         public override bool CanConvert(System.Type typeToConvert) { throw null; }
         public abstract T? Read(ref System.Text.Json.Utf8JsonReader reader, System.Type typeToConvert, System.Text.Json.JsonSerializerOptions options);
+        public virtual T ReadAsPropertyName(ref System.Text.Json.Utf8JsonReader reader, System.Type typeToConvert, System.Text.Json.JsonSerializerOptions options) { throw null; }
         public abstract void Write(
             System.Text.Json.Utf8JsonWriter writer,
 #nullable disable
             T value,
 #nullable restore
             System.Text.Json.JsonSerializerOptions options);
+        public virtual void WriteAsPropertyName(System.Text.Json.Utf8JsonWriter writer, T value, System.Text.Json.JsonSerializerOptions options) { }
     }
     [System.AttributeUsageAttribute(System.AttributeTargets.Field | System.AttributeTargets.Property, AllowMultiple=false)]
     public sealed partial class JsonExtensionDataAttribute : System.Text.Json.Serialization.JsonAttribute

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

@@ -55,7 +55,7 @@ protected internal override bool OnWriteResume(
                 {
                     state.Current.PropertyState = StackFramePropertyState.Name;
                     TKey key = enumerator.Current.Key;
-                    _keyConverter.WriteAsPropertyName(writer, key, options, ref state);
+                    _keyConverter.WriteAsPropertyNameCore(writer, key, options, state.Current.IsWritingExtensionDataProperty);
                 }
 
                 TValue element = enumerator.Current.Value;

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

@@ -61,7 +61,7 @@ protected internal override bool OnWriteResume(
                 do
                 {
                     TKey key = enumerator.Current.Key;
-                    _keyConverter.WriteAsPropertyName(writer, key, options, ref state);
+                    _keyConverter.WriteAsPropertyNameCore(writer, key, options, state.Current.IsWritingExtensionDataProperty);
                     _valueConverter.Write(writer, enumerator.Current.Value, options);
                 } while (enumerator.MoveNext());
             }
@@ -80,7 +80,7 @@ protected internal override bool OnWriteResume(
                         state.Current.PropertyState = StackFramePropertyState.Name;
 
                         TKey key = enumerator.Current.Key;
-                        _keyConverter.WriteAsPropertyName(writer, key, options, ref state);
+                        _keyConverter.WriteAsPropertyNameCore(writer, key, options, state.Current.IsWritingExtensionDataProperty);
                     }
 
                     TValue element = enumerator.Current.Value;

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

@@ -92,13 +92,13 @@ protected internal override bool OnWriteResume(Utf8JsonWriter writer, TDictionar
                     if (key is string keyString)
                     {
                         _keyConverter ??= GetConverter<string>(typeInfo.KeyTypeInfo!);
-                        _keyConverter.WriteAsPropertyName(writer, keyString, options, ref state);
+                        _keyConverter.WriteAsPropertyNameCore(writer, keyString, options, state.Current.IsWritingExtensionDataProperty);
                     }
                     else
                     {
                         // IDictionary is a special case since it has polymorphic object semantics on serialization
                         // but needs to use JsonConverter<string> on deserialization.
-                        _valueConverter.WriteAsPropertyName(writer, key, options, ref state);
+                        _valueConverter.WriteAsPropertyNameCore(writer, key, options, state.Current.IsWritingExtensionDataProperty);
                     }
                 }
 

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

@@ -252,16 +252,17 @@ TKey ReadDictionaryKey(ref Utf8JsonReader reader, ref ReadStack state)
                 TKey key;
                 string unescapedPropertyNameAsString;
 
+                _keyConverter ??= GetConverter<TKey>(state.Current.JsonTypeInfo.KeyTypeInfo!);
+
                 // Special case string to avoid calling GetString twice and save one allocation.
-                if (KeyType == typeof(string))
+                if (_keyConverter.IsInternalConverter && KeyType == typeof(string))
                 {
                     unescapedPropertyNameAsString = reader.GetString()!;
                     key = (TKey)(object)unescapedPropertyNameAsString;
                 }
                 else
                 {
-                    _keyConverter ??= GetConverter<TKey>(state.Current.JsonTypeInfo.KeyTypeInfo!);
-                    key = _keyConverter.ReadAsPropertyName(ref reader, typeToConvert, options);
+                    key = _keyConverter.ReadAsPropertyNameCore(ref reader, KeyType, options);
                     unescapedPropertyNameAsString = reader.GetString()!;
                 }
 

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Value/BooleanConverter.cs

@@ -17,7 +17,7 @@ public override void Write(Utf8JsonWriter writer, bool value, JsonSerializerOpti
             writer.WriteBooleanValue(value);
         }
 
-        internal override bool ReadAsPropertyName(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        internal override bool ReadAsPropertyNameCore(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
         {
             ReadOnlySpan<byte> propertyName = reader.GetSpan();
             if (Utf8Parser.TryParse(propertyName, out bool value, out int bytesConsumed)
@@ -29,7 +29,7 @@ internal override bool ReadAsPropertyName(ref Utf8JsonReader reader, Type typeTo
             throw ThrowHelper.GetFormatException(DataType.Boolean);
         }
 
-        internal override void WriteAsPropertyName(Utf8JsonWriter writer, bool value, JsonSerializerOptions options, ref WriteStack state)
+        internal override void WriteAsPropertyNameCore(Utf8JsonWriter writer, bool value, JsonSerializerOptions options, bool isWritingExtensionDataProperty)
         {
             writer.WritePropertyName(value);
         }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Value/ByteConverter.cs

@@ -20,12 +20,12 @@ public override void Write(Utf8JsonWriter writer, byte value, JsonSerializerOpti
             writer.WriteNumberValue(value);
         }
 
-        internal override byte ReadAsPropertyName(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        internal override byte ReadAsPropertyNameCore(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
         {
             return reader.GetByteWithQuotes();
         }
 
-        internal override void WriteAsPropertyName(Utf8JsonWriter writer, byte value, JsonSerializerOptions options, ref WriteStack state)
+        internal override void WriteAsPropertyNameCore(Utf8JsonWriter writer, byte value, JsonSerializerOptions options, bool isWritingExtensionDataProperty)
         {
             writer.WritePropertyName(value);
         }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Value/CharConverter.cs

@@ -28,10 +28,10 @@ public override void Write(Utf8JsonWriter writer, char value, JsonSerializerOpti
                 );
         }
 
-        internal override char ReadAsPropertyName(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        internal override char ReadAsPropertyNameCore(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
             => Read(ref reader, typeToConvert, options);
 
-        internal override void WriteAsPropertyName(Utf8JsonWriter writer, char value, JsonSerializerOptions options, ref WriteStack state)
+        internal override void WriteAsPropertyNameCore(Utf8JsonWriter writer, char value, JsonSerializerOptions options, bool isWritingExtensionDataProperty)
         {
             writer.WritePropertyName(
 #if BUILDING_INBOX_LIBRARY

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Value/DateTimeConverter.cs

@@ -15,12 +15,12 @@ public override void Write(Utf8JsonWriter writer, DateTime value, JsonSerializer
             writer.WriteStringValue(value);
         }
 
-        internal override DateTime ReadAsPropertyName(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        internal override DateTime ReadAsPropertyNameCore(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
         {
             return reader.GetDateTimeNoValidation();
         }
 
-        internal override void WriteAsPropertyName(Utf8JsonWriter writer, DateTime value, JsonSerializerOptions options, ref WriteStack state)
+        internal override void WriteAsPropertyNameCore(Utf8JsonWriter writer, DateTime value, JsonSerializerOptions options, bool isWritingExtensionDataProperty)
         {
             writer.WritePropertyName(value);
         }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Value/DateTimeOffsetConverter.cs

@@ -15,12 +15,12 @@ public override void Write(Utf8JsonWriter writer, DateTimeOffset value, JsonSeri
             writer.WriteStringValue(value);
         }
 
-        internal override DateTimeOffset ReadAsPropertyName(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        internal override DateTimeOffset ReadAsPropertyNameCore(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
         {
             return reader.GetDateTimeOffsetNoValidation();
         }
 
-        internal override void WriteAsPropertyName(Utf8JsonWriter writer, DateTimeOffset value, JsonSerializerOptions options, ref WriteStack state)
+        internal override void WriteAsPropertyNameCore(Utf8JsonWriter writer, DateTimeOffset value, JsonSerializerOptions options, bool isWritingExtensionDataProperty)
         {
             writer.WritePropertyName(value);
         }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Value/DecimalConverter.cs

@@ -20,12 +20,12 @@ public override void Write(Utf8JsonWriter writer, decimal value, JsonSerializerO
             writer.WriteNumberValue(value);
         }
 
-        internal override decimal ReadAsPropertyName(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        internal override decimal ReadAsPropertyNameCore(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
         {
             return reader.GetDecimalWithQuotes();
         }
 
-        internal override void WriteAsPropertyName(Utf8JsonWriter writer, decimal value, JsonSerializerOptions options, ref WriteStack state)
+        internal override void WriteAsPropertyNameCore(Utf8JsonWriter writer, decimal value, JsonSerializerOptions options, bool isWritingExtensionDataProperty)
         {
             writer.WritePropertyName(value);
         }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Value/DoubleConverter.cs

@@ -20,12 +20,12 @@ public override void Write(Utf8JsonWriter writer, double value, JsonSerializerOp
             writer.WriteNumberValue(value);
         }
 
-        internal override double ReadAsPropertyName(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        internal override double ReadAsPropertyNameCore(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
         {
             return reader.GetDoubleWithQuotes();
         }
 
-        internal override void WriteAsPropertyName(Utf8JsonWriter writer, double value, JsonSerializerOptions options, ref WriteStack state)
+        internal override void WriteAsPropertyNameCore(Utf8JsonWriter writer, double value, JsonSerializerOptions options, bool isWritingExtensionDataProperty)
         {
             writer.WritePropertyName(value);
         }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Value/EnumConverter.cs

@@ -84,7 +84,7 @@ public override T Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerial
                     return default;
                 }
 
-                return ReadAsPropertyName(ref reader, typeToConvert, options);
+                return ReadAsPropertyNameCore(ref reader, typeToConvert, options);
             }
 
             if (token != JsonTokenType.Number || !_converterOptions.HasFlag(EnumConverterOptions.AllowNumbers))
@@ -304,7 +304,7 @@ private string FormatEnumValueToString(string value, JavaScriptEncoder? encoder)
             return converted;
         }
 
-        internal override T ReadAsPropertyName(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        internal override T ReadAsPropertyNameCore(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
         {
             string? enumString = reader.GetString();
 
@@ -318,7 +318,7 @@ internal override T ReadAsPropertyName(ref Utf8JsonReader reader, Type typeToCon
             return value;
         }
 
-        internal override void WriteAsPropertyName(Utf8JsonWriter writer, T value, JsonSerializerOptions options, ref WriteStack state)
+        internal override void WriteAsPropertyNameCore(Utf8JsonWriter writer, T value, JsonSerializerOptions options, bool isWritingExtensionDataProperty)
         {
             // An EnumConverter that invokes this method
             // can only be created by JsonSerializerOptions.GetDictionaryKeyConverter
@@ -330,7 +330,7 @@ internal override void WriteAsPropertyName(Utf8JsonWriter writer, T value, JsonS
             // Try to obtain values from caches
             if (options.DictionaryKeyPolicy != null)
             {
-                Debug.Assert(!state.Current.IgnoreDictionaryKeyPolicy);
+                Debug.Assert(!isWritingExtensionDataProperty);
 
                 if (_dictionaryKeyPolicyCache != null && _dictionaryKeyPolicyCache.TryGetValue(key, out JsonEncodedText formatted))
                 {
@@ -344,7 +344,6 @@ internal override void WriteAsPropertyName(Utf8JsonWriter writer, T value, JsonS
                 return;
             }
 
-
             // if there are not cached values
             string original = value.ToString();
             if (IsValidIdentifier(original))

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Value/GuidConverter.cs

@@ -15,12 +15,12 @@ public override void Write(Utf8JsonWriter writer, Guid value, JsonSerializerOpti
             writer.WriteStringValue(value);
         }
 
-        internal override Guid ReadAsPropertyName(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        internal override Guid ReadAsPropertyNameCore(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
         {
             return reader.GetGuidNoValidation();
         }
 
-        internal override void WriteAsPropertyName(Utf8JsonWriter writer, Guid value, JsonSerializerOptions options, ref WriteStack state)
+        internal override void WriteAsPropertyNameCore(Utf8JsonWriter writer, Guid value, JsonSerializerOptions options, bool isWritingExtensionDataProperty)
         {
             writer.WritePropertyName(value);
         }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Value/Int16Converter.cs

@@ -21,12 +21,12 @@ public override void Write(Utf8JsonWriter writer, short value, JsonSerializerOpt
             writer.WriteNumberValue((long)value);
         }
 
-        internal override short ReadAsPropertyName(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        internal override short ReadAsPropertyNameCore(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
         {
             return reader.GetInt16WithQuotes();
         }
 
-        internal override void WriteAsPropertyName(Utf8JsonWriter writer, short value, JsonSerializerOptions options, ref WriteStack state)
+        internal override void WriteAsPropertyNameCore(Utf8JsonWriter writer, short value, JsonSerializerOptions options, bool isWritingExtensionDataProperty)
         {
             writer.WritePropertyName(value);
         }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Value/Int32Converter.cs

@@ -21,12 +21,12 @@ public override void Write(Utf8JsonWriter writer, int value, JsonSerializerOptio
             writer.WriteNumberValue((long)value);
         }
 
-        internal override int ReadAsPropertyName(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        internal override int ReadAsPropertyNameCore(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
         {
             return reader.GetInt32WithQuotes();
         }
 
-        internal override void WriteAsPropertyName(Utf8JsonWriter writer, int value, JsonSerializerOptions options, ref WriteStack state)
+        internal override void WriteAsPropertyNameCore(Utf8JsonWriter writer, int value, JsonSerializerOptions options, bool isWritingExtensionDataProperty)
         {
             writer.WritePropertyName(value);
         }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Value/Int64Converter.cs

@@ -20,12 +20,12 @@ public override void Write(Utf8JsonWriter writer, long value, JsonSerializerOpti
             writer.WriteNumberValue(value);
         }
 
-        internal override long ReadAsPropertyName(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        internal override long ReadAsPropertyNameCore(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
         {
             return reader.GetInt64WithQuotes();
         }
 
-        internal override void WriteAsPropertyName(Utf8JsonWriter writer, long value, JsonSerializerOptions options, ref WriteStack state)
+        internal override void WriteAsPropertyNameCore(Utf8JsonWriter writer, long value, JsonSerializerOptions options, bool isWritingExtensionDataProperty)
         {
             writer.WritePropertyName(value);
         }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Value/ObjectConverter.cs

@@ -30,13 +30,13 @@ public override void Write(Utf8JsonWriter writer, object? value, JsonSerializerO
             writer.WriteEndObject();
         }
 
-        internal override object ReadAsPropertyName(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        internal override object ReadAsPropertyNameCore(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
         {
             ThrowHelper.ThrowNotSupportedException_DictionaryKeyTypeNotSupported(TypeToConvert, this);
             return null!;
         }
 
-        internal override void WriteAsPropertyName(Utf8JsonWriter writer, object? value, JsonSerializerOptions options, ref WriteStack state)
+        internal override void WriteAsPropertyNameCore(Utf8JsonWriter writer, object? value, JsonSerializerOptions options, bool isWritingExtensionDataProperty)
         {
             // This converter does not handle nulls.
             Debug.Assert(value != null);
@@ -48,7 +48,7 @@ internal override void WriteAsPropertyName(Utf8JsonWriter writer, object? value,
                 ThrowHelper.ThrowNotSupportedException_DictionaryKeyTypeNotSupported(runtimeType, this);
             }
 
-            runtimeConverter.WriteAsPropertyNameAsObject(writer, value, options, ref state);
+            runtimeConverter.WriteAsPropertyNameCoreAsObject(writer, value, options, isWritingExtensionDataProperty);
         }
 
         internal override object? ReadNumberWithCustomHandling(ref Utf8JsonReader reader, JsonNumberHandling handling, JsonSerializerOptions options)

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Value/SByteConverter.cs

@@ -20,12 +20,12 @@ public override void Write(Utf8JsonWriter writer, sbyte value, JsonSerializerOpt
             writer.WriteNumberValue(value);
         }
 
-        internal override sbyte ReadAsPropertyName(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        internal override sbyte ReadAsPropertyNameCore(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
         {
             return reader.GetSByteWithQuotes();
         }
 
-        internal override void WriteAsPropertyName(Utf8JsonWriter writer, sbyte value, JsonSerializerOptions options, ref WriteStack state)
+        internal override void WriteAsPropertyNameCore(Utf8JsonWriter writer, sbyte value, JsonSerializerOptions options, bool isWritingExtensionDataProperty)
         {
             writer.WritePropertyName(value);
         }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Value/SingleConverter.cs

@@ -21,12 +21,12 @@ public override void Write(Utf8JsonWriter writer, float value, JsonSerializerOpt
             writer.WriteNumberValue(value);
         }
 
-        internal override float ReadAsPropertyName(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        internal override float ReadAsPropertyNameCore(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
         {
             return reader.GetSingleWithQuotes();
         }
 
-        internal override void WriteAsPropertyName(Utf8JsonWriter writer, float value, JsonSerializerOptions options, ref WriteStack state)
+        internal override void WriteAsPropertyNameCore(Utf8JsonWriter writer, float value, JsonSerializerOptions options, bool isWritingExtensionDataProperty)
         {
             writer.WritePropertyName(value);
         }