feat: use T -> R type converters for T? -> R? convert

[DevNico]

This will allow usage of T -> R mappers where a mapping of T? -> R? is required. This could technically be a breaking change if someone expected to have null be set instead of the mapped value.

[tenhobi]

Hello again! I will check this on Monday in more detail. The logic and basically mitigation of how input parameter and return value works in functions is discussed here #128 (comment)

But I will take a look at this case. Could you maybe provide more detail with why etc? 😊

[DevNico]

Sure, after reading #128 (comment) I don't think that it's currently possible to write a single TypeConverter to cover both T -> R and T? -> R? at the same time? The only one that would do that is a TypeConverter<Object?, Object> which I cannot implement for my use case because if my input is null I want my output to be null aswell.

Short example:

class ExampleId extends ValueId<int, ExampleId> {
  const ExampleId(super.value);
}

@AutoMappr(
  [],
  converters: [
    TypeConverter<int, ExampleId>(ExampleId.new),
  ],
)
class ExampleMappr extends $ExampleMappr{
  const ExampleMappr();
}

Sidenote the overview given in #128 (comment) might help some people if it was in the readme.

[tenhobi]

First of all, we can add that list to readme, good point!

---

I see now, "TypeConverter<Object?, Object>, ... if my input is null I want my output to be null as well".

I extended the support for this also for TypeConverter<Object, Object?>

Aka the proposed change is

• TypeConverter<Object, Object> ... aka Object converter(Object) => ...
  • Object -> Object
  • Object -> Object?
  • Object? -> Object?, when source is not null <-- THIS
• TypeConverter<Object, Object?> ... aka Object? converter(Object) => ...
  • Object -> Object?
  • Object? -> Object? when source is not null <-- THIS
• TypeConverter<Object?, Object> ... aka Object converter(Object?) => ...
  • Object -> Object
  • Object? -> Object
  • Object -> Object?
  • Object? -> Object?
• TypeConverter<Object?, Object?> ... aka Object? converter(Object?) => ...
  • Object -> Object?
  • Object? -> Object?

[tenhobi]

I am also thinking, should there be an option to disable/enable this, or should we keep it always on?

[DevNico]

I am also thinking, should there be an option to disable/enable this, or should we keep it always on?

I do think that the change should always be enabled by default but I am not sure if this is a breaking change. Might be best to release as a new major version. I do not see why one would want to turn this feature off so a feature flag / build configuration value thingy isn't required unless someone asks for it in the future I guess.

[tenhobi]

LGTM, thanks for the great work @DevNico