I agree, Dart's public-facing codegen system (build_runner) leaves a lot to be desired. (In part the problem is that Dart uses a separate system inside Google.)

However, this is a topic of active work for the Dart team: https://github.com/dart-lang/build/issues/3800. I'm sure they would welcome your feedback, particularly if you have examples you can share.

You're also always welcome to reach out to me if you have Flutter/Dart concerns. I founded the Flutter project (and briefly led the Dart team) and care a great deal about customer success with both. eric@shorebird.dev reaches me.

It takes a minute to build from scratch or to update when running "build_runner watch"? My app is over 40k lines and watch updates almost instantaneously.

You should be able to leverage generate_for in your build.yaml with include/exclude to reduce those build times significantly. You should be able to get it back down to a few seconds including building the graph and then you should be able to just run watch instead of build.

It may be worth mentioning that build_runner's graph contains every single asset that might be generated. So when selecting what's included and excluded you can reduce the graph size dramatically.