I already fixed most of the issues found by checkstyle here. The remaining issues required more thoughts and maybe discussion. And I already prepared the 1.3.0 release in #19398 (moved). But if you prefer fixing most or even all issues, I'm happy to delay the 1.3.0 release. What do you think?
I'll attach a patch to #19398 (moved) that fixes all but three checkstyle complaints.
The two remaining switch-without-default definitely need new tests and probably discussion.
These can be tackled on this issue, which now can wait for a release > 1.3.0.