Derived attribute causes exception

[SteveDunn]

Describe the bug

This should work:

public class CustomValueObjectAttribute<T> : ValueObjectAttribute<T>
{
    public CustomValueObjectAttribute(
        Conversions conversions = Conversions.Default | Conversions.EfCoreValueConverter,
        CastOperator toPrimitiveCasting = CastOperator.Implicit,
        CastOperator fromPrimitiveCasting = CastOperator.Implicit,
        ComparisonGeneration comparisonGeneration = ComparisonGeneration.Omit)
    { }
}

... but it fails
This is currently failing with InvalidCastException.

[CustomValueObject<Guid>]
public readonly partial record struct ConversationId
{
}

Generator 'ValueObjectGenerator' failed to generate source. It will not contribute to the output and compilation errors may occur as a result. Exception was of type 'InvalidCastException' with message 'Unable to cast object of type 'System.Int32' to type 'Microsoft.CodeAnalysis.INamedTypeSymbol'.'

Vogen v4.0.17

Steps to reproduce

Use the code above

Expected behaviour

No exceptions

[SteveDunn]

Unfortunately, derived attributes must include all of the parameter from the base attribute. So in your case, it's this immensely verbose declaration!

public class CustomValueObjectAttribute<T> : ValueObjectAttribute<T>
{
    public CustomValueObjectAttribute(
        Conversions conversions = Conversions.Default | Conversions.EfCoreValueConverter,
        Type? throws = null,
        Customizations customizations = Customizations.None,
        DeserializationStrictness deserializationStrictness = DeserializationStrictness.AllowValidAndKnownInstances,
        DebuggerAttributeGeneration debuggerAttributes = DebuggerAttributeGeneration.Default,
        ComparisonGeneration comparison = ComparisonGeneration.Omit,
        StringComparersGeneration stringComparers = StringComparersGeneration.Unspecified,
        CastOperator toPrimitiveCasting = CastOperator.Implicit,
        CastOperator fromPrimitiveCasting = CastOperator.Implicit,
        ParsableForStrings parsableForStrings = ParsableForStrings.Unspecified,
        ParsableForPrimitives parsableForPrimitives = ParsableForPrimitives.Unspecified,
        TryFromGeneration tryFromGeneration = TryFromGeneration.Unspecified,
        IsInitializedMethodGeneration isInitializedMethodGeneration = IsInitializedMethodGeneration.Unspecified,
        PrimitiveEqualityGeneration primitiveEqualityGeneration = PrimitiveEqualityGeneration.Unspecified)
        : base(
            conversions, throws, customizations, deserializationStrictness, debuggerAttributes, comparison, stringComparers,
            toPrimitiveCasting, fromPrimitiveCasting, parsableForStrings, parsableForPrimitives, tryFromGeneration,
            isInitializedMethodGeneration, primitiveEqualityGeneration)
    {
    }
}

It should be something like this, which is more natural, but Vogen doesn't currently support:

    public CustomValueObjectAttribute(
        Conversions conversions = Conversions.Default | Conversions.EfCoreValueConverter,
        ComparisonGeneration comparison = ComparisonGeneration.Omit,
        CastOperator toPrimitiveCasting = CastOperator.Implicit,
        CastOperator fromPrimitiveCasting = CastOperator.Implicit)
    : base(conversions: conversions, comparison: comparison, toPrimitiveCasting: toPrimitiveCasting, fromPrimitiveCasting: fromPrimitiveCasting)
    {
    }

This is because Vogen reads constructor parameters in order, rather than by name. So it expects the 14th parameter to be pf a certain type, the 13th to be of a certain type, etc. etc. In the case of this bug, the parameter at position 1 was expected to be a type (of the exception that is thrown during validation), but instead was an integer (representing the constant value of an enum).

I need to have a think about a better way to handle this, maybe:

[VogenConfig<Guid>]
public partial class CustomValueObject
{
        public readonly Conversions conversions = Conversions.Default | Conversions.EfCoreValueConverter;
        public readonly ComparisonGeneration comparison = ComparisonGeneration.Omit;
        public readonly CastOperator toPrimitiveCasting = CastOperator.Implicit;
        public readonly CastOperator fromPrimitiveCasting = CastOperator.Implicit;
}

That would then generate a `CustomValueObject<Guid>` attribute

I don't think this change is going to happen within the next couple of weeks though, so it looks like the ugly verbose way is the best way.

Mind you, if it's **assembly wide** config, then you can use the `[assembly: VogenDefaults(...)]`, but as I say, that's per-assembly.