Remove `@TagNumber(...)` annotations?

[devoncarew]

I'm unclear what the @$pb.TagNumber(104) annotations are used for. Thay add quite a bit of noise to the generated code - each message field is tagged w/ four TagNumber annotations.

  /// Used as a ...
  @$pb.TagNumber(103)
  $core.String get apiShortName => $_getSZ(2);
  @$pb.TagNumber(103)
  set apiShortName($core.String v) {
    $_setString(2, v);
  }

  @$pb.TagNumber(103)
  $core.bool hasApiShortName() => $_has(2);
  @$pb.TagNumber(103)
  void clearApiShortName() => $_clearField(103);

Do we know of any use cases / users of these annotations? (or, if they are being used, why we're tagging all for items for the field instead of just something like the getter)

The docs for the annotation say; 'Annotation for marking accessors that belong together.\n\nAllows tooling to associate related accessors'.

cc @osa1 (and also @sigurdm, who may also have context here)

[sigurdm]

They are used by the "protobuf aware treeshaker" https://github.com/dart-lang/sdk/blob/617d0a8e96edbbff9f1c76f873bdcd74f39f5b1a/pkg/vm/bin/protobuf_aware_treeshaker.dart#L6 to see which fields are related to which accessors.

Recognized here:
https://github.com/dart-lang/sdk/blob/617d0a8e96edbbff9f1c76f873bdcd74f39f5b1a/pkg/vm/lib/transformations/type_flow/protobuf_handler.dart#L76

[osa1]

I think we should document the use cases in annotations (also for GrpcServiceName) in documentation comments. Currently it's impossible to find out why they're needed as the uses are not even in the same library.

[devoncarew]

Thanks for the links! I may dig into the code to see if we can safely dial back the annotations a bit (are they necessary on the hazzers and the clear method as well?).

[sigurdm]

The idea is that if we don't use any of the accessors for one field, we can remove out the descriptor, that in turn might enable us to treeshake other things.

But maybe there is a less verbose way of marking the connection.

[devoncarew]

Gotcha; if the only use was through a 'clearXXX' method, and that wasn't annotated, the tree-shaker would miss the reference.