Performance problems which combined with json_serializable

[lume-code]

For a long time, some of our applications suffered from long build_runner incremental builds. However, with the recent introduction of build_runner logging, it appears that source_gen:combining_builder, which runs after freezed and json_serializable, is the main culprit. It seems that build_runner itself is working on improving this issue (dart-lang/build#3803). Nevertheless, I would like to ask the author of the freezed library about immediate approaches we might take to mitigate the problem for now. Interestingly, this step goes through all the files in the project, even those that neither have a freezed nor json_serializable instance in them, and significantly increases the incremental build times. Is this intended behavior? During this long runs I am seeing logs like lib/features/payment/data/repositories/payment_repository.mock.freezed.dart although this file is not a freezed one at all.