Add StringEnumReader which converts strings to StringEnums

Because we serialize with json.net and deserialize with System.Text.Json (involuntarily through jsruntime), we need a write-converter for json.net and a read-converter for system.text.json. sadly a lot of features are not yet present in system.text.json and so we can't use one converter attribute for the base-class but need one for every enum. This should change in .Net 5; progress is tracked at https://github.com/dotnet/corefx/issues/39905.

src/ChartJs.Blazor/ChartJS/Common/Enums/AxisType.cs

@@ -1,8 +1,12 @@
-namespace ChartJs.Blazor.ChartJS.Common.Enums
+using ChartJs.Blazor.ChartJS.Common.Enums.JsonConverter;
+using System.Text.Json.Serialization;
+
+namespace ChartJs.Blazor.ChartJS.Common.Enums
 {
     /// <summary>
     /// As per documentation here https://www.chartjs.org/docs/latest/axes/cartesian/
     /// </summary>
+    [JsonConverter(typeof(JsonStringEnumReader<AxisType>))]
     public sealed class AxisType : StringEnum
     {
         /// <summary>

src/ChartJs.Blazor/ChartJS/Common/Enums/BorderAlign.cs

@@ -1,9 +1,13 @@
-namespace ChartJs.Blazor.ChartJS.Common.Enums
+using ChartJs.Blazor.ChartJS.Common.Enums.JsonConverter;
+using System.Text.Json.Serialization;
+
+namespace ChartJs.Blazor.ChartJS.Common.Enums
 {
     /// <summary>
     /// Specifies the border alignment of a <see cref="PieChart"/> and a <see cref="PolarAreaChart"/>.
     /// <para>As per documentation here https://www.chartjs.org/docs/latest/charts/doughnut.html#border-alignment </para>
     /// </summary>
+    [JsonConverter(typeof(JsonStringEnumReader<BorderAlign>))]
     public sealed class BorderAlign : StringEnum
     {
         /// <summary>

src/ChartJs.Blazor/ChartJS/Common/Enums/BorderCapStyle.cs

@@ -1,9 +1,13 @@
-namespace ChartJs.Blazor.ChartJS.Common.Enums
+using ChartJs.Blazor.ChartJS.Common.Enums.JsonConverter;
+using System.Text.Json.Serialization;
+
+namespace ChartJs.Blazor.ChartJS.Common.Enums
 {
     /// <summary>
     /// Specifies the border cap style.
     /// <para>As per documentation here https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/lineCap </para>
     /// </summary>
+    [JsonConverter(typeof(JsonStringEnumReader<BorderCapStyle>))]
     public sealed class BorderCapStyle : StringEnum
     {
         /// <summary>

src/ChartJs.Blazor/ChartJS/Common/Enums/BorderJoinStyle.cs

@@ -1,9 +1,13 @@
-namespace ChartJs.Blazor.ChartJS.Common.Enums
+using ChartJs.Blazor.ChartJS.Common.Enums.JsonConverter;
+using System.Text.Json.Serialization;
+
+namespace ChartJs.Blazor.ChartJS.Common.Enums
 {
     /// <summary>
     /// Specifies the border join style.
     /// <para>As per documentation here https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/lineJoin </para>
     /// </summary>
+    [JsonConverter(typeof(JsonStringEnumReader<BorderJoinStyle>))]
     public sealed class BorderJoinStyle : StringEnum
     {
         /// <summary>

src/ChartJs.Blazor/ChartJS/Common/Enums/ChartType.cs

@@ -1,8 +1,12 @@
-namespace ChartJs.Blazor.ChartJS.Common.Enums
+using ChartJs.Blazor.ChartJS.Common.Enums.JsonConverter;
+using System.Text.Json.Serialization;
+
+namespace ChartJs.Blazor.ChartJS.Common.Enums
 {
     /// <summary>
     /// Defines the chart types.
     /// </summary>
+    [JsonConverter(typeof(JsonStringEnumReader<ChartType>))]
     public sealed class ChartType : StringEnum
     {
         /// <summary>

src/ChartJs.Blazor/ChartJS/Common/Enums/CubicInterpolationMode.cs

@@ -1,9 +1,13 @@
-namespace ChartJs.Blazor.ChartJS.Common.Enums
+using ChartJs.Blazor.ChartJS.Common.Enums.JsonConverter;
+using System.Text.Json.Serialization;
+
+namespace ChartJs.Blazor.ChartJS.Common.Enums
 {
     /// <summary>
     /// Specifies the cubic interpolation mode.
     /// <para>As per documentation here https://www.chartjs.org/docs/latest/charts/line.html#cubicinterpolationmode </para>
     /// </summary>
+    [JsonConverter(typeof(JsonStringEnumReader<CubicInterpolationMode>))]
     public sealed class CubicInterpolationMode : StringEnum
     {
         /// <summary>

src/ChartJs.Blazor/ChartJS/Common/Enums/FontStyle.cs

@@ -1,9 +1,13 @@
+using ChartJs.Blazor.ChartJS.Common.Enums.JsonConverter;
+using System.Text.Json.Serialization;
+
 namespace ChartJs.Blazor.ChartJS.Common.Enums
 {
     /// <summary>
     /// Specifies the css font style of text.
     /// <para>As per documentation here https://developer.mozilla.org/en-US/docs/Web/CSS/font-style </para>
     /// </summary>
+    [JsonConverter(typeof(JsonStringEnumReader<FontStyle>))]
     public sealed class FontStyle : StringEnum
     {
         /// <summary>

src/ChartJs.Blazor/ChartJS/Common/Enums/InteractionMode.cs

@@ -1,8 +1,12 @@
-namespace ChartJs.Blazor.ChartJS.Common.Enums
+using ChartJs.Blazor.ChartJS.Common.Enums.JsonConverter;
+using System.Text.Json.Serialization;
+
+namespace ChartJs.Blazor.ChartJS.Common.Enums
 {
     /// <summary>
     /// As per documentation here https://www.chartjs.org/docs/latest/general/interactions/modes.html
     /// </summary>
+    [JsonConverter(typeof(JsonStringEnumReader<InteractionMode>))]
     public sealed class InteractionMode : StringEnum
     {
         /// <summary>

src/ChartJs.Blazor/ChartJS/Common/Enums/JsonConverter/JsonObjectEnumConverter.cs → src/ChartJs.Blazor/ChartJS/Common/Enums/JsonConverter/JsonObjectEnumWriter.cs

@@ -3,9 +3,9 @@
 namespace ChartJs.Blazor.ChartJS.Common.Enums.JsonConverter
 {
     /// <summary>
-    /// JsonConverter for converting and writing an ObjectEnum value. This JsonConverter can only write.
+    /// Newtonsoft JsonConverter for writing an <see cref="ObjectEnum"/> value. This JsonConverter can only write.
     /// </summary>
-    internal class JsonObjectEnumConverter : JsonWriteOnlyConverter<ObjectEnum>
+    internal class JsonObjectEnumWriter : JsonWriteOnlyConverter<ObjectEnum>
     {
         public override void WriteJson(JsonWriter writer, ObjectEnum wrapper, JsonSerializer serializer)
         {

src/ChartJs.Blazor/ChartJS/Common/Enums/JsonConverter/JsonStringEnumReader.cs

@@ -0,0 +1,39 @@
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Reflection;
+using System.Text;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace ChartJs.Blazor.ChartJS.Common.Enums.JsonConverter
+{
+    // we need T and the constraint because the you can't use JsonConverter for the base-class
+    // https://github.com/dotnet/corefx/issues/39905
+    /// <summary>
+    /// System.Text.Json JsonConverter for reading <see cref="StringEnum"/>s. The <see cref="StringEnum"/> is created via reflection
+    /// and does not take in account what values actually exist in the "enum". This is not a big deal
+    /// because the values that are deserialized using this converter should only come from chart.js and should be mapped correctly
+    /// to an "enum"-value in that <see cref="StringEnum"/>.
+    /// </summary>
+    /// <typeparam name="T">The type of <see cref="StringEnum"/> this converter is for. This is required because System.Text.Json
+    /// doesn't allow converters for base-classes yet.</typeparam>
+    internal class JsonStringEnumReader<T> : JsonConverter<T>
+        where T : StringEnum
+    {
+        private static readonly ConcurrentDictionary<Type, ConstructorInfo> s_constructorCache = new ConcurrentDictionary<Type, ConstructorInfo>();
+
+        public override T Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        {
+            ConstructorInfo constructor = s_constructorCache.GetOrAdd(typeToConvert,
+                type => type.GetConstructor(BindingFlags.Instance | BindingFlags.NonPublic, null, new[] { typeof(string) }, null));
+
+            return (T)constructor.Invoke(new[] { reader.GetString() });
+        }
+
+        public override void Write(Utf8JsonWriter writer, T value, JsonSerializerOptions options)
+        {
+            throw new NotImplementedException();
+        }
+    }
+}

src/ChartJs.Blazor/ChartJS/Common/Enums/JsonConverter/JsonStringEnumConverter.cs → src/ChartJs.Blazor/ChartJS/Common/Enums/JsonConverter/JsonStringEnumWriter.cs

@@ -3,9 +3,9 @@
 namespace ChartJs.Blazor.ChartJS.Common.Enums.JsonConverter
 {
     /// <summary>
-    /// JsonConverter for converting and writing a StringEnum value. This JsonConverter can only write.
+    /// Newtonsoft JsonConverter for writing a <see cref="StringEnum"/> value. This JsonConverter can only write.
     /// </summary>
-    internal class JsonStringEnumConverter : JsonWriteOnlyConverter<StringEnum>
+    internal class JsonStringEnumWriter : JsonWriteOnlyConverter<StringEnum>
     {
         public override void WriteJson(JsonWriter writer, StringEnum value, JsonSerializer serializer)
         {

src/ChartJs.Blazor/ChartJS/Common/Enums/ObjectEnum.cs

@@ -6,7 +6,7 @@ namespace ChartJs.Blazor.ChartJS.Common.Enums
     /// <summary>
     /// Inherit this class if you are in need of a pseudo-Enum which can hold values of different kinds (eg. string, double and bool).
     /// </summary>
-    [JsonConverter(typeof(JsonObjectEnumConverter))]
+    [JsonConverter(typeof(JsonObjectEnumWriter))]
     public abstract class ObjectEnum
     {
         /// <summary>

src/ChartJs.Blazor/ChartJS/Common/Enums/PointStyle.cs

@@ -1,11 +1,15 @@
 
+using ChartJs.Blazor.ChartJS.Common.Enums.JsonConverter;
+using System.Text.Json.Serialization;
+
 namespace ChartJs.Blazor.ChartJS.Common.Enums
 {
     /// <summary>
     /// Specifies how a data-point on the chart will be styled.
     /// <para>As per documentation here https://www.chartjs.org/docs/latest/configuration/elements.html#point-styles </para>
     /// <para>Some samples showcasing the different styles can be found here https://www.chartjs.org/samples/latest/charts/line/point-styles.html </para>
     /// </summary>
+    [JsonConverter(typeof(JsonStringEnumReader<PointStyle>))]
     public sealed class PointStyle : StringEnum
     {
         /// <summary>

src/ChartJs.Blazor/ChartJS/Common/Enums/Position.cs

@@ -1,8 +1,12 @@
-namespace ChartJs.Blazor.ChartJS.Common.Enums
+using ChartJs.Blazor.ChartJS.Common.Enums.JsonConverter;
+using System.Text.Json.Serialization;
+
+namespace ChartJs.Blazor.ChartJS.Common.Enums
 {
     /// <summary>
     /// Represents a relative direction or position on a 2D canvas.
     /// </summary>
+    [JsonConverter(typeof(JsonStringEnumReader<Position>))]
     public sealed class Position : StringEnum
     {
 #pragma warning disable CS1591 // Missing XML comment for publicly visible type or member

src/ChartJs.Blazor/ChartJS/Common/Enums/ScaleBound.cs

@@ -1,9 +1,13 @@
-namespace ChartJs.Blazor.ChartJS.Common.Enums
+using ChartJs.Blazor.ChartJS.Common.Enums.JsonConverter;
+using System.Text.Json.Serialization;
+
+namespace ChartJs.Blazor.ChartJS.Common.Enums
 {
     /// <summary>
     /// Specifies the scale boundary strategy.
     /// <para>As per documentation here https://www.chartjs.org/docs/latest/axes/cartesian/time.html#scale-bounds </para>
     /// </summary>
+    [JsonConverter(typeof(JsonStringEnumReader<ScaleBound>))]
     public sealed class ScaleBound : StringEnum
     {
         /// <summary>

src/ChartJs.Blazor/ChartJS/Common/Enums/StringEnum.cs

@@ -1,9 +1,11 @@
-using Newtonsoft.Json;
+using System;
+using System.Text.Json;
+using System.Text.Json.Serialization;
 using ChartJs.Blazor.ChartJS.Common.Enums.JsonConverter;
 
 namespace ChartJs.Blazor.ChartJS.Common.Enums
 {
-    [JsonConverter(typeof(JsonStringEnumConverter))]
+    [Newtonsoft.Json.JsonConverter(typeof(JsonStringEnumWriter))]
     public abstract class StringEnum
     {
         private readonly string _value;

src/ChartJs.Blazor/ChartJS/Common/Enums/TickSource.cs

@@ -1,8 +1,12 @@
-namespace ChartJs.Blazor.ChartJS.Common.Enums
+using ChartJs.Blazor.ChartJS.Common.Enums.JsonConverter;
+using System.Text.Json.Serialization;
+
+namespace ChartJs.Blazor.ChartJS.Common.Enums
 {
     /// <summary>
     /// As per documentation here https://www.chartjs.org/docs/latest/axes/cartesian/time.html#ticks-source
     /// </summary>
+    [JsonConverter(typeof(JsonStringEnumReader<TickSource>))]
     public sealed class TickSource : StringEnum
     {
         /// <summary>

src/ChartJs.Blazor/ChartJS/Common/Enums/TimeDistribution.cs

@@ -1,9 +1,13 @@
 
+using ChartJs.Blazor.ChartJS.Common.Enums.JsonConverter;
+using System.Text.Json.Serialization;
+
 namespace ChartJs.Blazor.ChartJS.Common.Enums
 {
     /// <summary>
     /// As per documentation here https://www.chartjs.org/docs/latest/axes/cartesian/time.html#scale-distribution
     /// </summary>
+    [JsonConverter(typeof(JsonStringEnumReader<TimeDistribution>))]
     public sealed class TimeDistribution : StringEnum
     {
         /// <summary>

src/ChartJs.Blazor/ChartJS/Common/Enums/TimeMeasurement.cs

@@ -1,11 +1,15 @@
-namespace ChartJs.Blazor.ChartJS.Common.Enums
+using ChartJs.Blazor.ChartJS.Common.Enums.JsonConverter;
+using System.Text.Json.Serialization;
+
+namespace ChartJs.Blazor.ChartJS.Common.Enums
 {
     /// <summary>
     /// As per documentation here https://www.chartjs.org/docs/latest/axes/cartesian/time.html#time-units
     /// </summary>
-    /// 
+    [JsonConverter(typeof(JsonStringEnumReader<TimeMeasurement>))]
     public sealed class TimeMeasurement : StringEnum
     {
+#pragma warning disable CS1591 // Missing XML comment for publicly visible type or member
         public static TimeMeasurement Millisecond => new TimeMeasurement("millisecond");
         public static TimeMeasurement Second => new TimeMeasurement("second");
         public static TimeMeasurement Minute => new TimeMeasurement("minute");
@@ -15,6 +19,7 @@ public sealed class TimeMeasurement : StringEnum
         public static TimeMeasurement Month => new TimeMeasurement("month");
         public static TimeMeasurement Quarter => new TimeMeasurement("quarter");
         public static TimeMeasurement Year => new TimeMeasurement("year");
+#pragma warning restore CS1591 // Missing XML comment for publicly visible type or member
 
         private TimeMeasurement(string stringRep) : base(stringRep) { }
     }

src/ChartJs.Blazor/ChartJS/Common/Enums/TooltipPosition.cs

@@ -1,9 +1,13 @@
-namespace ChartJs.Blazor.ChartJS.Common.Enums
+using ChartJs.Blazor.ChartJS.Common.Enums.JsonConverter;
+using System.Text.Json.Serialization;
+
+namespace ChartJs.Blazor.ChartJS.Common.Enums
 {
     /// <summary>
     /// Specifies where the tooltip will be displayed.
     /// <para>As per documentation here https://www.chartjs.org/docs/latest/configuration/tooltip.html#position-modes </para>
     /// </summary>
+    [JsonConverter(typeof(JsonStringEnumReader<TooltipPosition>))]
     public sealed class TooltipPosition : StringEnum
     {
         /// <summary>