Enum Attribute arguments are stored as Type Object

[xumix]

Which leads to problems like inability to get the enum value name when working with Attribute arguments. I think that better alternative is to store them as IEnumValue so that it is possible to get useful info from the value.

[NeVeSpl]

Do you mean an enum type used as an attribute argument? It would be nice to see c# code snippet to remove any chance for misunderstanding.

[xumix]

Do you mean an enum type used as an attribute argument? It would be nice to see c# code snippet to remove any chance for misunderstanding.

    [AttributeUsage(AttributeTargets.Field, AllowMultiple = true)]
    public class StatisticsGroupAttribute : Attribute
    {
        protected StatisticsGroupAttribute(StatisticsGroupTypeEnum type, params object[] values)
        {
            var ids = new List<Guid>();

            Type = type;

            foreach (var value in values)
            {
                if (value is Enum @enum)
                {
                    ids.Add(@enum.GetId());
                }
                else
                {
                    throw new ArgumentException($"'{value}' не является '{nameof(Enum)}'", nameof(value));
                }
            }

            Values = ids;
        }

        public StatisticsGroupAttribute(StatisticsGroupTypeEnum type, params RegionStatTypeEnum[] values)
            : this(type, values.Cast<object>().ToArray())
        {
        }

        public StatisticsGroupAttribute(StatisticsGroupTypeEnum type, params FederalLawEnum[] values)
            : this(type, values.Cast<object>().ToArray())
        {
        }

        public StatisticsGroupTypeEnum Type { get; set; }

        public IEnumerable<Guid> Values { get; }
    }

Usage:

    public enum RegionStatTypeEnum
    {
        [Display(Name = "Число контрактов по 44-ФЗ, заключенных по результатам КС")]
        [StatisticsGroup(StatisticsGroupTypeEnum.Restriction, FederalLawEnum.FZ44)]
        AuctionContractCount44,

        [Display(Name = "Сумма по всем контрактам")]
        [StatisticsGroup(StatisticsGroupTypeEnum.Variation, ContractSum223, ContractSum44)]
        ContractSum,
}

When I try to get the StatisticsGroupAttribute Arguments I get type object containing int as a value

var args = enumValue.Attributes.First(f => f.Name == "StatisticsGroup").Arguments;

so I can't get what it the actual type of the argument

[NeVeSpl]

I have made a unit test:

input code:

namespace NTypewriter.Tests.CodeModel
{
    public enum RegionStatTypeEnum
    {        
        [StatisticsGroup(StatisticsGroupTypeEnum.Restriction, FederalLawEnum.FZ44)]
        AuctionContractCount44,

        [StatisticsGroup(StatisticsGroupTypeEnum.Variation, 2, FederalLawEnum.FZ69)]
        ContractSum,
    }

    [AttributeUsage(AttributeTargets.Field, AllowMultiple = true)]
    public class StatisticsGroupAttribute : Attribute
    {
        public StatisticsGroupAttribute(StatisticsGroupTypeEnum type, params object[] values)
        {

        }       

        public StatisticsGroupAttribute(StatisticsGroupTypeEnum type, params FederalLawEnum[] values)
            : this(type, values.Cast<object>().ToArray())
        {
        }

        public StatisticsGroupTypeEnum Type { get; set; }

        public IEnumerable<Guid> Values { get; }
    }

    public enum StatisticsGroupTypeEnum
    {
        Restriction = 1,
        Variation = 3,
    }

    public enum FederalLawEnum
    {
        FZ44 = 44,
        FZ69 = 69,
    }
}

template:

{{- capture captured}}
{{- for enum in data.Enums | Symbols.WhereNamespaceStartsWith "NTypewriter.Tests.CodeModel" | Symbols.WhereNameEndsWith "RegionStatTypeEnum"}}
    {{- for enum_item in enum.Values }} 
    {{-  enum_item.Name}}
         {{- for attr in enum_item.Attributes }}
[{{ attr.Name }}] 
         {{- for arg in attr.Arguments }}
             name : {{ arg.Name }} 
             type : {{ arg.Type }}
             value : {{ arg.Value }}
             -------------
         {{~ end}}
         {{- end }}
    {{- end}}
{{ end }}
{{- end }}
{{- Save captured "result" }}

output:

AuctionContractCount44
[StatisticsGroup]
             name : type 
             type : StatisticsGroupTypeEnum
             value : StatisticsGroupTypeEnum.Restriction
             -------------

             name : values 
             type : FederalLawEnum[]
             value : [44]
             -------------
ContractSum
[StatisticsGroup]
             name : type 
             type : StatisticsGroupTypeEnum
             value : StatisticsGroupTypeEnum.Variation
             -------------

             name : values 
             type : object[]
             value : [2, 69]
             -------------

As you can see there is no problem with determining the type of argument of an attribute. The only problem that I see is inconsistency:

• for arrays of enums there is returned array of enum values
• for a single variable of enum type there is returned enum type.value name

IEnumValue cannot be used here, because the parameters of attributes are TypedConstant, a completely different type.

[NeVeSpl]

NTypewriter will follow Roslyn design and return ITypedConstant for the value of the attribute argument.

In the upcoming version for the input from previous comment, the output will be:

AuctionContractCount44
[StatisticsGroup]
             name : type 
             type : StatisticsGroupTypeEnum
             value : StatisticsGroupTypeEnum.Restriction
             -------------

             name : values 
             type : FederalLawEnum[]
             value : [FederalLawEnum.FZ44]
             -------------
ContractSum
[StatisticsGroup]
             name : type 
             type : StatisticsGroupTypeEnum
             value : StatisticsGroupTypeEnum.Variation
             -------------

             name : values 
             type : object[]
             value : [2, FederalLawEnum.FZ69]
             -------------

[xumix]

Thank you so much, I'll try this!