Nullable error when target type comes from external reference

[PaulVrugt]

Describe the bug
Nullable error when target type comes from external reference

To Reproduce
Steps to reproduce the behavior:
Download the sample project from #679

Expected behavior
No nullable erros

Code snippets
source:

public class Source
{
    public SubSource[]? Property1 { get; set; }
}

public class SubSource
{
    public Guid Id { get; set; }
}

and a mapper:

[Mapper]
internal static partial class EntityMapper
{
    internal static partial Target ToMutationIssue(Source issueDto);
}

and the target, but this target is included via a references project:

public class Target
{
    public SubTarget[]? Property1 { get; set; }
}

public class SubTarget
{
    public Guid Id { get; set; }
}

Environment (please complete the following information):

• Mapperly Version: 3.1.0
• .NET Version: .net 7
• Target Framework: .net 7
• IDE: Visual Studio v17.6.6
• OS: windows 11

Additional context
It only happens when the target class is in a references project

[latonz]

I can reproduce the issue, but I don't really understand it.
The relevant generated code looks like this:

...
if (issueDto.Property1 != null)
{
     target.Property1 = MapToSubTargetArray(issueDto.Property1);
}
...
private static global::dtoTest.SubTarget[] MapToSubTargetArray(global::NullableMapperlyTest.SubSource[] source)
...

The compiler reports error CS8619: Nullability of reference types in value of type 'SubTarget?[]' doesn't match target type 'SubTarget[]', but the generated method returns global::dtoTest.SubTarget[] and has a #nullable enable directive at the top. If I copy the generated mapper into a cs file into the project and comment the [Mapper] attribute it works just fine. Although the referenced project has nullables enabled and the property on the target is of type SubTarget[]?, and not SubTarget?[] as the compiler reports. I'm not sure if this is really a problem of Mapperly or if it is a problem of Roslyn. Especially since the generated code works 1:1 if copied to the the project for which it is generated.

@TimothyMakkison what are your thoughts on this?

[PaulVrugt]

Yeah my brain also crashed investigating what was going wrong. But the problem in our case is that ALL dto's are coming from a referenced project, and we treat all warnings as errors in our project, so this issue is preventing our code base to build.

As far as I could find mapperly doesn't have an option to disable nullable context in the generated code does it? Because that would be a workaround for us for the time being

[latonz]

@PaulVrugt nope Mapperly doesn't have such an option. The problem only exiss on arrays, correct?

Sorry that you can't use Mapperly for now 🙄

[TimothyMakkison]

The nullability being on the array element threw me + the difference between VS and rider.

Perhaps in external references, arrays don't correctly annotate array element/generic types, so they all annotated with None. This is then upgraded to Annotated by mapperly.

I'm strugglng to debug this. I can recreate the issue if I look at the generated code. Running it in debug mode generates the following code with no nullability issues 😭

public static partial global::Lib.ContainerDto MapTo(global::Riok.Mapperly.Sample.Container src)
{
    var target = new global::Lib.ContainerDto();
    target.Arrays = MapToElementDtoArray(src.Arrays);
    return target;
}
private static global::Lib.ElementDto MapToElementDto(global::Riok.Mapperly.Sample.Element source)
{
    var target = new global::Lib.ElementDto();
    target.Value = source.Value;
    return target;
}
private static global::Lib.ElementDto[] MapToElementDtoArray(global::Riok.Mapperly.Sample.Element[] source)
{
    var target = new global::Lib.ElementDto[source.Length];
    for (var i = 0; i < source.Length; i++)
    {
        target[i] = MapToElementDto(source[i]);
    }

    return target;
}

[TimothyMakkison]

I think I've fixed the issue. Looks like external array types treat the nullability of type arguments differently. Not sure if this is a roslyn bug 🤷

I realised that the same issue wouldn't occur if the external collection is a list, despite having similar code generated.

// returns a `None` annotated generic type if type is an array
 if (type.ImplementsGeneric(types.Get(typeof(IEnumerable<>)), out var enumerableIntf))
            return enumerableIntf.TypeArguments[0];

// will have the correct nullability annotation
((IArrayTypeSymbol)type).ElementType;

I'm strugglng to debug this. I can recreate the issue if I look at the generated code. Running it in debug mode generates the following code with no nullability issues 😭

I ended up creating a static public static List<String> Logger {get:} which would insert comments to the end of the final MemberDeclarationSyntax in SourceEmitter

[PaulVrugt]

Awesome! Hopefully this fixes it

[github-actions]

🎉 This issue has been resolved in version 3.2.0-next.2 🎉

The release is available on:

• GitHub release
• v3.2.0-next.2

Your semantic-release bot 📦🚀

[github-actions]

🎉 This issue has been resolved in version 3.2.0 🎉

The release is available on:

• GitHub release
• v3.2.0

Your semantic-release bot 📦🚀