[ruby-core:104905] [Ruby master Feature#17881] Add a Module#const_added callback
From:
takashikkbn@...
Date:
2021-08-13 06:35:46 UTC
List:
ruby-core #104905
Issue #17881 has been updated by k0kubun (Takashi Kokubun). Status changed from Open to Feedback FYI, I changed the MJIT implementation in commit:ac4d53bd461ff386cd45fdd484ffb6b628a251ad to not disable JIT-ed code when a TracePoint for class events gets enabled. So, as long as Zeitwerk only uses TracePoints for class events, we no longer need this API for MJIT w/ Zeitwerk either. ---------------------------------------- Feature #17881: Add a Module#const_added callback https://bugs.ruby-lang.org/issues/17881#change-93266 * Author: byroot (Jean Boussier) * Status: Feedback * Priority: Normal ---------------------------------------- ### Use case Autoloaders like `zeitwerk` need a callback when a new class or module is registered in the constant table. Currently this is implemented with TracePoint's `:class` event. It works, but it is a bit unfortunate to have to use an API intended for debugging to implement production features. It doesn't feel "conceptually clean". It also [doesn't play well with MJIT](https://k0kubun.medium.com/ruby-3-jit-can-make-rails-faster-756310f235a), even though it's more of an MJIT limitation. Additionally this usage of TracePoint cause [some incompatibilities with some debuggers like `byebug`](https://github.com/deivid-rodriguez/byebug/issues/564) (even though others don't have this issue). ### Proposal I believe that if Ruby was to call `Module#const_added` when a constant is registered, Zeitwerk could get rid of TracePoint. For now I implemented it as: `const_added(const_name)` for similarity with `method_added`. But maybe it could make sense to have the signature be `const_added(const_name, const_value)`. Also since `method_removed` exists, maybe `const_removed` would need to be added for consistency. ### Links Patch: https://github.com/ruby/ruby/pull/4521 Zeitwerk side discussion: https://github.com/fxn/zeitwerk/issues/135 cc @k0kubun -- https://bugs.ruby-lang.org/ Unsubscribe: <mailto:ruby-core-request@ruby-lang.org?subject=unsubscribe> <http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>