From: eregontp@... Date: 2021-05-22T12:18:05+00:00 Subject: [ruby-core:103978] [Ruby master Feature#17881] Add a Module#const_added callback Issue #17881 has been updated by Eregon (Benoit Daloze). Ugh, Redmine doesn't handle posting a comment concurrently and now incorrectly reverted the description changes even though I didn't touch the description. @byroot Could you re-apply your changes? ---------------------------------------- Feature #17881: Add a Module#const_added callback https://bugs.ruby-lang.org/issues/17881#change-92111 * Author: byroot (Jean Boussier) * Status: Open * 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 also has performance implications (albeit relatively minor), and [doesn't play well with MJIT](https://k0kubun.medium.com/ruby-3-jit-can-make-rails-faster-756310f235a). ### 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: