When implementing the attachment mechanism suggested by @marandaneto in #683, I realize BeforeSendCallback has a nullable Hint. If the passed-in hint is null, I have no way to attach an attachment. On the other hand, I quickly glanced through the source code and it seems that it guarantees it is not null (by providing a default value). So shall we mark it as non-null?

Platform

Dart

Obfuscation

Enabled

Debug Info

Enabled

Doctor

Version

latest

Steps to Reproduce

Expected Result

Actual Result

Are you willing to submit a PR?

None