EnumMember is not applied when enum value is a combination of flags.

[filzrev]

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Describe the bug When serialize enum value combinations. value is serialized by default enum name. And the name that is specified by EnumMember is not used.

To Reproduce

Test Code

[Flags]
public enum TestEnum
{
	[JsonStringEnumMemberName("A")]
	[EnumMember(Value = "A")]
	AAA = 1,
	[JsonStringEnumMemberName("B")]
	[EnumMember(Value = "B")]
	BBB = 2,
}

public class Tests
{
    [Fact]
    public void YamlDotNetTest()
    {
          var serializer = new SerializerBuilder().Build();

          // Arrange
          var value = TestEnum.AAA | TestEnum.BBB;

          // Act
          var result = serializer.Serialize(value);

          // Assert
          result.Should().Be("A, B\r\n"); // Failed. Expected: "A,B\r\n" but Actual: "AAA, BBB\r\n"
    }
}

Serialize result of System.Text.Json / NewtonsoftJson

When serialize same value with System.Text.Json / NewtonsoftJson enum value is serialized as expected.

// System.Text.Json use `JsonStringEnumMemberName` attribute (EnumMember attribute is not used)
[Fact]
public void SystemTextJsonTest()
{	
	var options = new JsonSerializerOptions { };
	options.Converters.Add(new JsonStringEnumConverter(JsonNamingPolicy.CamelCase));
	
	// Arrange
	var value = TestEnum.AAA | TestEnum.BBB;

	// Act
	var result = System.Text.Json.JsonSerializer.Serialize(value, options);

	// Assert
	result.Should().Be("\"A, B\""); // Success
}

// NewtonsoftJson use `EnumMember` attribute.
[Fact]
public void NewtonsoftJsonTest()
{
	// Arrange
	var value = TestEnum.AAA | TestEnum.BBB;

	// Act
	var result = JsonConvert.SerializeObject(value, new Newtonsoft.Json.Converters.StringEnumConverter());

	// Assert
	result.Should().Be("\"A, B\""); // Success
}