ruby/debug is a new debugger that is going to ship with CRuby.
It makes sense for Rails to switch to this one because that is
where the language is heading, and because Byebug is not fully
compatible with Zeitwerk. See
https://github.com/deivid-rodriguez/byebug/issues/564
While ruby/debug has not been heavily tested with Zeitwerk,
casual usage seems to suggest it works without issues, including
explicit namespaces, which is where Byebug and Zeitwerk conflict.
Byebug is terrific, thanks a lot for all these years. ❤️
`Minitest.plugin_rails_init` sets `Minitest.backtrace_filter` to
`Rails.backtrace_cleaner` right before tests are run, overwriting the
value set in test_helper.rb.
`Rails.backtrace_cleaner` silences backtrace lines that do not start
with `Rails.root` followed by e.g. "lib/" or "test/". Thus when
`Rails.root` is a subdirectory of the project directory -- for example,
when testing a plugin that has a dummy app -- all lines of the backtrace
are silenced.
This commit adds a fallback such that when all backtrace lines are
silenced, the original `Minitest.backtrace_filter` is used instead.
Additionally, this commit refactors and expands existing test coverage.
