add tests showing TypeConverterGeneric<T> is working when used without factory

Author: StefanBertels

tests/CsvHelper.Tests/TypeConversion/TypeConverterFactoryTests.cs

@@ -0,0 +1,107 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Globalization;
+using System.IO;
+using System.Linq;
+using CsvHelper.Configuration;
+using CsvHelper.TypeConversion;
+using Xunit;
+
+namespace CsvHelper.Tests.TypeConversion
+{
+	public class TypeConverterFactoryTests
+	{
+		public readonly record struct Option<T> : IEnumerable<T>
+		{
+			public bool IsPresent { get; }
+			private readonly T _value;
+
+			internal Option(T value)
+			{
+				IsPresent = true;
+				_value = value;
+			}
+
+			public IEnumerator<T> GetEnumerator()
+			{
+				if (IsPresent) yield return _value;
+			}
+
+			IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+		}
+
+		private class MyOptionTypeFactory : ITypeConverterFactory
+		{
+			public bool CanCreate(Type type) =>
+				type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Option<>);
+
+			public bool Create(Type type, TypeConverterCache cache, out ITypeConverter typeConverter)
+			{
+				var wrappedType = type.GetGenericArguments().Single();
+				typeConverter =
+					Activator.CreateInstance(typeof(OptionConverter<>).MakeGenericType(wrappedType)) as
+						ITypeConverter ?? throw new NullReferenceException();
+				return true;
+			}
+
+			internal class OptionConverter<T> : TypeConverterGeneric<Option<T>>
+			{
+				public override string ConvertToString(Option<T> value, IWriterRow row,
+					MemberMapData memberMapData)
+				{
+					var wrappedTypeConverter = row.Context.TypeConverterCache.GetConverter<T>();
+					return value.IsPresent
+						? wrappedTypeConverter.ConvertToString(value.Single(), row, memberMapData)
+						: "";
+				}
+
+				public override Option<T> ConvertFromString(string text, IReaderRow row,
+					MemberMapData memberMapData)
+				{
+					var wrappedTypeConverter = row.Context.TypeConverterCache.GetConverter<T>();
+
+					return text == ""
+						? new Option<T>()
+						: new Option<T>((T)wrappedTypeConverter.ConvertFromString(text, row, memberMapData));
+				}
+			}
+		}
+
+		private record RecordWithGenerics(Option<int> MaybeNumber);
+
+		[Fact]
+		void ReadTypeConverterGenericInt()
+		{
+			var input = """
+			            MaybeNumber
+			            23
+
+			            """;
+
+			using var cr = new CsvReader(new StringReader(input), CultureInfo.InvariantCulture);
+			cr.Context.TypeConverterCache.AddConverter(new MyOptionTypeFactory.OptionConverter<int>());
+			var firstRow = cr.GetRecords<RecordWithGenerics>().First();
+			Assert.Equal(new Option<int>(23), firstRow.MaybeNumber);
+		}
+
+		[Fact]
+		void WriteTypeConverterGenericInt()
+		{
+			var expected = """
+			               MaybeNumber
+			               42
+
+			               """;
+
+			var stringWriter = new StringWriter();
+			using var cw = new CsvWriter(stringWriter, CultureInfo.InvariantCulture);
+			cw.Context.TypeConverterCache.AddConverter(new MyOptionTypeFactory.OptionConverter<int>());
+			cw.WriteRecords(new[]
+			{
+				new RecordWithGenerics(new Option<int>(42))
+			});
+			Assert.Equal(expected, stringWriter.ToString());
+		}
+	}
+}