Fix custom floating-point JSON converters

Directory.Build.props

@@ -28,7 +28,7 @@
   </PropertyGroup>
 
   <PropertyGroup>
-    <LangVersion>latest</LangVersion>
+    <LangVersion>preview</LangVersion>
     <!-- Default Version numbers -->
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
     <IsPackable>false</IsPackable>

src/Elastic.Clients.Elasticsearch/Serialization/DefaultSourceSerializer.cs

@@ -22,7 +22,7 @@ public class DefaultSourceSerializer : SystemTextJsonSerializer
 	{
 		new JsonStringEnumConverter(),
 		new DoubleWithFractionalPortionConverter(),
-		new FloatWithFractionalPortionConverter()
+		new SingleWithFractionalPortionConverter()
 	};
 
 	private readonly JsonSerializerOptions _jsonSerializerOptions;

src/Elastic.Clients.Elasticsearch/Serialization/DoubleWithFractionalPortionConverter.cs

@@ -2,89 +2,121 @@
 // Elasticsearch B.V licenses this file to you under the Apache 2.0 License.
 // See the LICENSE file in the project root for more information.
 
-#pragma warning disable IDE0005
 using System;
+
+#if NETCOREAPP
+
 using System.Buffers.Text;
+
+#endif
+
 using System.Globalization;
+
+#if !NETCOREAPP
+
 using System.Text;
+
+#endif
+
 using System.Text.Json;
 using System.Text.Json.Serialization;
-using static Elastic.Clients.Elasticsearch.Serialization.JsonConstants;
-#pragma warning restore IDE0005
 
 namespace Elastic.Clients.Elasticsearch.Serialization;
 
 internal sealed class DoubleWithFractionalPortionConverter : JsonConverter<double>
 {
-	// We don't handle floating point literals (NaN, etc.) because for source serialization because Elasticsearch only support finite values for numeric fields.
-	// We must handle the possibility of numbers as strings in the source however.
-
 	public override double Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
 	{
-		if (reader.TokenType == JsonTokenType.String && options.NumberHandling.HasFlag(JsonNumberHandling.AllowReadingFromString))
+		if (reader.TokenType != JsonTokenType.String)
+			return reader.GetDouble();
+
+		if (options.NumberHandling.HasFlag(JsonNumberHandling.AllowNamedFloatingPointLiterals))
+		{
+			// TODO: Handle 'reader.HasValueSequence'
+			if (reader.ValueSpan.SequenceEqual(JsonConstants.LiteralNaN))
+				return float.NaN;
+			if (reader.ValueSpan.SequenceEqual(JsonConstants.LiteralPositiveInfinity))
+				return float.PositiveInfinity;
+			if (reader.ValueSpan.SequenceEqual(JsonConstants.LiteralNegativeInfinity))
+				return float.NegativeInfinity;
+		}
+
+		if (options.NumberHandling.HasFlag(JsonNumberHandling.AllowReadingFromString))
 		{
 			var value = reader.GetString();
 
-			if (!double.TryParse(value, NumberStyles.Any, CultureInfo.InvariantCulture, out var parsedValue))
+			if (!double.TryParse(value, NumberStyles.Any, CultureInfo.InvariantCulture, out var result))
 				ThrowHelper.ThrowJsonException($"Unable to parse '{value}' as a double.");
 
-			return parsedValue;
+			return result;
 		}
 
 		return reader.GetDouble();
 	}
 
 	public override void Write(Utf8JsonWriter writer, double value, JsonSerializerOptions options)
 	{
-		Span<byte> utf8bytes = stackalloc byte[128]; // This is the size used in STJ for future proofing. https://github.com/dotnet/runtime/blob/dae6c2472b699b7cff2efeb5ce06b75c9551bc40/src/libraries/System.Text.Json/src/System/Text/Json/JsonConstants.cs#L79
+		if (options.NumberHandling.HasFlag(JsonNumberHandling.AllowNamedFloatingPointLiterals))
+		{
+			switch (value)
+			{
+				case double.NaN:
+					writer.WriteStringValue(JsonConstants.EncodedNaN);
+					return;
 
-		// NOTE: This code is based on https://github.com/dotnet/runtime/blob/dae6c2472b699b7cff2efeb5ce06b75c9551bc40/src/libraries/System.Text.Json/src/System/Text/Json/JsonConstants.cs#L79
+				case double.PositiveInfinity:
+					writer.WriteStringValue(JsonConstants.EncodedPositiveInfinity);
+					return;
+
+				case double.NegativeInfinity:
+					writer.WriteStringValue(JsonConstants.EncodedNegativeInfinity);
+					return;
+			}
+		}
 
-		// Frameworks that are not .NET Core 3.0 or higher do not produce round-trippable strings by
-		// default. Further, the Utf8Formatter on older frameworks does not support taking a precision
-		// specifier for 'G' nor does it represent other formats such as 'R'. As such, we duplicate
-		// the .NET Core 3.0 logic of forwarding to the UTF16 formatter and transcoding it back to UTF8,
-		// with some additional changes to remove dependencies on Span APIs which don't exist downlevel.
+		if (options.NumberHandling.HasFlag(JsonNumberHandling.WriteAsString))
+		{
+			// TODO: Implement as needed
+			throw new NotImplementedException("The 'JsonNumberHandling.WriteAsString' is currently not supported.");
+		}
 
-		// PERFORMANCE: This code could be benchmarked and tweaked to make it faster.
+		// This code is based on:
+		// https://github.com/dotnet/runtime/blob/main/src/libraries/System.Text.Json/src/System/Text/Json/Writer/Utf8JsonWriter.WriteValues.Double.cs#L101
 
 #if NETCOREAPP
-		if (Utf8Formatter.TryFormat(value, utf8bytes, out var bytesWritten))
+		Span<byte> utf8Text = stackalloc byte[JsonConstants.MaximumFormatDoubleLength];
+
+		if (Utf8Formatter.TryFormat(value, utf8Text, out var bytesWritten, JsonConstants.DoubleStandardFormat))
 		{
-			if (utf8bytes.IndexOfAny(NonIntegerBytes) == -1)
+			if (utf8Text.IndexOfAny(JsonConstants.NonIntegerChars) == -1)
 			{
-				utf8bytes[bytesWritten++] = (byte)'.';
-				utf8bytes[bytesWritten++] = (byte)'0';
+				utf8Text[bytesWritten++] = (byte)'.';
+				utf8Text[bytesWritten++] = (byte)'0';
 			}
 
-#pragma warning disable IDE0057 // Use range operator
-			writer.WriteRawValue(utf8bytes.Slice(0, bytesWritten), skipInputValidation: true);
-#pragma warning restore IDE0057 // Use range operator
-
+			writer.WriteRawValue(utf8Text[..bytesWritten], true);
 			return;
 		}
 #else
-		var utf16Text = value.ToString("G17", CultureInfo.InvariantCulture);
+		var utf16Text = value.ToString(JsonConstants.DoubleFormatString, CultureInfo.InvariantCulture);
+		if (utf16Text.IndexOfAny(JsonConstants.NonIntegerChars) == -1)
+		{
+			utf16Text += ".0";
+		}
 
-		if (utf16Text.Length < utf8bytes.Length)
+		try
 		{
-			try
-			{
-				var bytes = Encoding.UTF8.GetBytes(utf16Text);
+			var utf8Text = Encoding.UTF8.GetBytes(utf16Text);
 
-				if (bytes.Length < utf8bytes.Length)
-				{
-					bytes.CopyTo(utf8bytes);
-					return;
-				}
-			}
-			catch
-			{
-				// Swallow this and fall through to our general exception.
-			}
+			writer.WriteRawValue(utf8Text, true);
+			return;
+		}
+		catch
+		{
+			// Swallow this and fall through to our general exception.
 		}
 #endif
 
-		ThrowHelper.ThrowJsonException($"Unable to serialize double value.");
+		ThrowHelper.ThrowJsonException("Unable to serialize double value.");
 	}
 }

src/Elastic.Clients.Elasticsearch/Serialization/JsonConstants.cs

@@ -3,12 +3,39 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
+using System.Text.Json;
+
+#if NETCOREAPP
+
+using System.Buffers;
+
+#endif
 
 namespace Elastic.Clients.Elasticsearch.Serialization;
 
 internal static class JsonConstants
 {
-#pragma warning disable IDE0230 // Use UTF-8 string literal
-	public static ReadOnlySpan<byte> NonIntegerBytes => new[] { (byte)'E', (byte)'.' }; // In the future, when we move to the .NET 7 SDK, it would be nice to use u8 literals e.g. "E."u8
-#pragma warning restore IDE0230 // Use UTF-8 string literal
+	public static ReadOnlySpan<byte> LiteralNaN => "NaN"u8;
+	public static ReadOnlySpan<byte> LiteralPositiveInfinity => "Infinity"u8;
+	public static ReadOnlySpan<byte> LiteralNegativeInfinity => "-Infinity"u8;
+	public static JsonEncodedText EncodedNaN => JsonEncodedText.Encode(LiteralNaN);
+	public static JsonEncodedText EncodedPositiveInfinity => JsonEncodedText.Encode(LiteralPositiveInfinity);
+	public static JsonEncodedText EncodedNegativeInfinity => JsonEncodedText.Encode(LiteralNegativeInfinity);
+
+#if NETCOREAPP
+	public static ReadOnlySpan<byte> NonIntegerChars => "E."u8;
+#else
+	public static char[] NonIntegerChars => new[] { 'E', '.' };
+#endif
+
+	public const string DoubleFormatString = "G17"; // 'R' does not roundtrip correctly in some cases prior to .NET Core 3
+	public const string SingleFormatString = "G9";  // https://learn.microsoft.com/en-us/dotnet/standard/base-types/standard-numeric-format-strings#round-trip-format-specifier-r
+
+#if NETCOREAPP
+	public static readonly StandardFormat DoubleStandardFormat = StandardFormat.Parse(DoubleFormatString);
+	public static readonly StandardFormat SingleStandardFormat = StandardFormat.Parse(SingleFormatString);
+
+	public const int MaximumFormatDoubleLength = 128; // https://github.com/dotnet/runtime/blob/main/src/libraries/System.Text.Json/src/System/Text/Json/JsonConstants.cs#L78
+	public const int MaximumFormatSingleLength = 128; // https://github.com/dotnet/runtime/blob/main/src/libraries/System.Text.Json/src/System/Text/Json/JsonConstants.cs#L79
+#endif
 }