There's --allow-warnings-in-packages and --allow-errors-in-packages to only show warnings of certain packages. This is useful for meta-packages like Flutter that only want to show warnings of the packages they control.

It would be nice if there's also an option to only show warnings/errors for a certain library. The use case in Flutter: we control the dart:ui library and want to make sure it is free of dartdoc warnings and errors. Unfortunately, dart:ui is bundled in the larger sky_engine package, which contains other dart: libraries that we don't control and those do contain some warnings that we would like to ignore. A --allow-warnings-in-libraries flag would help here.

When --allow-warnings-in-packages and --allow-warnings-in-libraries are used in combination, I'd imagine you'd get the warnings for all the libraries in the packages listed under the first flag plus the warnings for the libraries listed under the second flag.