I'm not sure if this is my fault, maybe I've simply failed at understanding the docs.

I need to export the database:

$ wp db export
mysqldump: Got error: 1044: "Access denied for user 'myuser'@'localhost' to database 'mydb'" when using LOCK TABLES

This is actually expected in my case, because I don't want to give the user that WP uses to connect to the database the LOCK TABLES privilege.

However I need the "wp db export" command to work when manually invoked from time to time.
I'm ok with manually specifying different username and password, using the "--<field>=<value>" syntax, but that fails too:

$ wp db export --user=root --password=mypass
mysqldump: Got error: 1045: "Access denied for user 'myuser'@'localhost' (using password: YES)" when trying to connect

which means wp cli handed only the "--password" option to mysqldump, but not the "--user" option. That's expected too, because the "--user" option is a global option that's used to specify the WordPress user, not the database user.

However I couldn't find any "--dbuser" or similar option: I'm not sure if that's by design or a missing feature, but I think it would make sense to have it in the latter case.