Consider adding a new reflection API to get field values of an Enum

[LakshanF]

The trimmer doesn't trim Enum fields. As mentioned in the comment here, it would make sense to have a separate API that doesn't require DynamicallyAccessedMembers annotation to get Enum fields. That would prevent suppressing the warning as done here when getting Enum fields.

[MichalPetryka]

Can't NativeAOT not generate reflection info for such fields?

[jkotas]

get field values of an Enum

Note that we have added trim and AOT friendly ways to get values of an Enum: Enum.GetValuesAsUnderlyingType - #72498.

The specific case in EnumConverter wants the field values presented as FieldInfos. Fetching enum values as FieldInfos is quite inefficient, but it is required here because of pre-existing public surface.

A new API can look like this:

public class Enum
{
    [UnconditionalSuppressMessage("Trimming", "IL2075:", Justification = "Trimmer does not trim Enums")]
    public static FieldInfo[] GetValuesAsFieldInfos(Type enumType)
    {
        ArgumentNullException.ThrowIfNull(enumType);

        if (!enumType.IsEnum)
            throw new ArgumentException(SR.Arg_MustBeEnum, "enumType")

       return enumType.GetFields(BindingFlags.Public | BindingFlags.Static);
    }

The question is whether fetching enum values as FieldInfos is common enough to warrant a new public API. I think we would want to see at least one or two additional cases from real-world code where this API can be used.

[eerhardt]

The question is whether fetching enum values as FieldInfos is common enough to warrant a new public API.

Here's another use case:

#97737

There we need to get the EnumMemberAttribute on the Field of an Enum.

[steveharter]

The specific case in EnumConverter wants the field values presented as FieldInfos. Fetching enum values as FieldInfos is quite inefficient, but it is required here because of pre-existing public surface.

The case in EnumConverter doesn't directly expose the FieldInfos but does check for [Browseable] attribute on the FieldInfo, so a new API is necessary here.

However, the case in EventSource could use Enum.GetValuesAsUnderlyingType() instead of FieldInfos as the FieldInfos used there are used temporarily + privately and do not check for the [Browseable] attribute.

Moving to V10; priority appears low here (removing a couple cases of UnconditionalSuppressMessage).

[eerhardt]

Here's one more hit on the same scenario:

https://github.com/microsoft/OpenAPI.NET/pull/1717/files#diff-c59c9153ccf5e00142826d1c5e4d3d92470aac0bc740a302a23557432141277cR29

Getting the DisplayAttribute of an enum field.