Third-party libraries that depend on dart_mappable without exporting mappers break code generation

[nikodembernat]

Issue

Let's assume we have a 3rd party package:some_package that depends on dart_mappable to generate model classes. That package then exports models, but hides mappers to avoid polluting the autocomplete (see: #91).

Now, let's move to our app. We create a class that uses those exported models in our own dart_mappable class. The current implementation fails during code generation, because the 3rd party library doesn't export *Mapper and *CopyWith classes, but expects them since those models are annotated with @MappableClass().

Related repository

n-bernat/dart_mappable-issue278

Possible solution

Since we can add custom mappers to @MappableClass() (e.g. @MappableClass(includeCustomMappers: [_SomeMapper()]), it seems feasible to use provided custom mappers (if we have them), instead of generating new ones.

[schultek]

As you correctly identified we need all third party mappers to be available in the library where our own class is defined. I think the best way is just for the third party package to export the mappers and copyWith classes as well.

To deal with the namespace "pollution" the package could have two top-level libraries, one with and one without exported mappers. Than in your model files you can import the library with mappers and everywhere else the one without.

I don't see another solution to this right now.