PostProcessBuilder class Null safety
A builder which runs in a special phase at the end of the build.
They are different from a normal Builder in several ways:
- They don't have to declare output extensions, and can output any file as long as it doesn't conflict with an existing one.
- They can only read their primary input.
- They will not cause optional actions to run - they will only run on assets that were built as a part of the normal build.
- They all run in a single phase, and thus can not see the outputs of any other PostProcessBuilders.
- Because they run in a separate phase, after other builders, none of thier outputs can be consumed by Builders.
Because of these restrictions, these builders should never be used to output Dart files, or any other file which would should be processed by normal Builders.