Issue #21143 has been updated by fxn (Xavier Noria). The hooks `const_added` and `inherited` may need to be executed "together". For example, consider: ```ruby module M def self.const_added(cname) = ... class C def self.inherited(subclass) = ... end class D < C; end end ``` When `D` is defined, two hooks are set to run, but in which order? Both orders make sense in a way: 1. When `inherited` is called, you can observe that the subclass has a permanent name, ergo it was assigned to a constant, which must me stored in a class or module object. Therefore, the constant was added to said module module before `inherited` was invoked. 1. When `const_added` is called, you can `const_get` the symbol and observe the object is a class, hence with a superclass, hence inheritance already happened. The patch in [ruby#12759](https://github.com/ruby/ruby/pull/12759) documents and adds a test for (1). Rationale: 1. I believe it would be nice specify this order. 1. Chose (1) because it is how it works today. While the motivation for the patch was formal (to remove an ambiguity), after reflecting about this I realized users of Zeitwerk may depend on this. Nowadays, Zeitwerk uses `const_added` to set autoloads for child constants in namespaces. Thanks to the current order, code can be used in `inherited` hooks normally (it would not be ready if the order was different). ---------------------------------------- Misc #21143: Speficy order of execution const_added vs inherited https://bugs.ruby-lang.org/issues/21143#change-111994 * Author: fxn (Xavier Noria) * Status: Open ---------------------------------------- The hooks `const_added` and `inherited` may need to be executed "together". For example, consider: ```ruby module M def self.const_added(cname) = ... class C def self.inherited(subclass) = ... end class D < C; end ``` When `D` is defined, two hooks are set to run, but in which order? Both orders make sense in a way: 1. When `inherited` is called, you can observe that the subclass has a permanent name, ergo it was assigned to a constant, which must me stored in a module. Therefore, the constant was added to said module module before `inherited` was invoked. 1. When `const_added` is called, you can `const_get` the symbol and observe the object is a class, hence with a superclass, hence inheritance already happened. The patch in https://github.com/ruby/ruby/pull/12759 documents and adds a test for (1). Rationale: 1. I believe it would be nice specify this order. 1. Chose (1) because it is how it works today. While the motivation for the patch was formal (to remove an ambiguity), after reflecting about this I realized users of Zeitwerk may depend on this. Zeitwerk uses `const_added` to set autoloads for child constants in namespaces. Thanks to the current order, code can be used in `inherited` hooks normally (it would not be ready if the order was different). -- https://bugs.ruby-lang.org/

Issue #21143 has been updated by Eregon (Benoit Daloze). FWIW looking at this stuff I noticed `rb_class_new()` doesn't call `inherited` at all, but `rb_define_class*()` do. ---------------------------------------- Misc #21143: Speficy order of execution const_added vs inherited https://bugs.ruby-lang.org/issues/21143#change-111998 * Author: fxn (Xavier Noria) * Status: Open ---------------------------------------- The hooks `const_added` and `inherited` may need to be executed "together". For example, consider: ```ruby module M def self.const_added(cname) = ... class C def self.inherited(subclass) = ... end class D < C; end end ``` When `D` is defined, two hooks are set to run, but in which order? Both orders make sense in a way: 1. When `inherited` is called, you can observe that the subclass has a permanent name, ergo it was assigned to a constant, which must me stored in a class or module object. Therefore, the constant was added to said class/module before `inherited` was invoked. 1. When `const_added` is called, you can `const_get` the symbol and observe the object is a class, hence with a superclass, hence inheritance already happened. The patch in [ruby#12759](https://github.com/ruby/ruby/pull/12759) documents and adds a test for (1). Rationale: 1. I believe it would be nice to specify this order. 1. Chose (1) because it is how it works today. While the motivation for the patch was formal (to remove an ambiguity), after reflecting about this I realized users of Zeitwerk may depend on this. Nowadays, Zeitwerk uses `const_added` to set autoloads for child constants in namespaces. Thanks to the current order, code can be used in `inherited` hooks normally (it would not be ready if the order was different). -- https://bugs.ruby-lang.org/

Issue #21143 has been updated by matz (Yukihiro Matsumoto). Status changed from Open to Feedback I think @eregon's opinion here is reasonable. But I don't want to break any existing code. I'd like to experiment `inherited`-then-`const_added` order works (or not). If it works, I'd like to change the order. If it doesn't I'like to keep the current order (and document somewhere). Matz. ---------------------------------------- Misc #21143: Speficy order of execution const_added vs inherited https://bugs.ruby-lang.org/issues/21143#change-112285 * Author: fxn (Xavier Noria) * Status: Feedback ---------------------------------------- The hooks `const_added` and `inherited` may need to be executed "together". For example, consider: ```ruby module M def self.const_added(cname) = ... class C def self.inherited(subclass) = ... end class D < C; end end ``` When `D` is defined, two hooks are set to run, but in which order? Both orders make sense in a way: 1. When `inherited` is called, you can observe that the subclass has a permanent name, ergo it was assigned to a constant, which must me stored in a class or module object. Therefore, the constant was added to said class/module before `inherited` was invoked. 1. When `const_added` is called, you can `const_get` the symbol and observe the object is a class, hence with a superclass, hence inheritance already happened. The patch in [ruby#12759](https://github.com/ruby/ruby/pull/12759) documents and adds a test for (1). Rationale: 1. I believe it would be nice to specify this order. 1. Chose (1) because it is how it works today. While the motivation for the patch was formal (to remove an ambiguity), after reflecting about this I realized users of Zeitwerk may depend on this. Nowadays, Zeitwerk uses `const_added` to set autoloads for child constants in namespaces. Thanks to the current order, code can be used in `inherited` hooks normally (it would not be ready if the order was different). -- https://bugs.ruby-lang.org/

Issue #21143 has been updated by byroot (Jean Boussier). Calling `inherited` before `const_added` is doable and I doubt it would cause much backward compatibility issues except for one thing: the class being anonymous when `inherited` is called. There are a number of `inherited` methods in Rails that do expect the class to have a name (it handles anonymous classes in a degraded way). Just to give one example: https://github.com/rails/rails/blob/3626b8f52c425c2dd7a0d0aa698cff9f10d789b3... Here `module_parents` rely on `Module#name`. But if we still assign the `name` before calling `inherited`, then I think we can change the order without problem. ---------------------------------------- Misc #21143: Speficy order of execution const_added vs inherited https://bugs.ruby-lang.org/issues/21143#change-112301 * Author: fxn (Xavier Noria) * Status: Feedback ---------------------------------------- The hooks `const_added` and `inherited` may need to be executed "together". For example, consider: ```ruby module M def self.const_added(cname) = ... class C def self.inherited(subclass) = ... end class D < C; end end ``` When `D` is defined, two hooks are set to run, but in which order? Both orders make sense in a way: 1. When `inherited` is called, you can observe that the subclass has a permanent name, ergo it was assigned to a constant, which must me stored in a class or module object. Therefore, the constant was added to said class/module before `inherited` was invoked. 1. When `const_added` is called, you can `const_get` the symbol and observe the object is a class, hence with a superclass, hence inheritance already happened. The patch in [ruby#12759](https://github.com/ruby/ruby/pull/12759) documents and adds a test for (1). Rationale: 1. I believe it would be nice to specify this order. 1. Chose (1) because it is how it works today. While the motivation for the patch was formal (to remove an ambiguity), after reflecting about this I realized users of Zeitwerk may depend on this. Nowadays, Zeitwerk uses `const_added` to set autoloads for child constants in namespaces. Thanks to the current order, code can be used in `inherited` hooks normally (it would not be ready if the order was different). -- https://bugs.ruby-lang.org/

Issue #21143 has been updated by fxn (Xavier Noria).

But if we still assign the name before calling inherited, then I think we can change the order without problem.

Just to clarify in the thread, it is more than the name. Nowadays, the constant exists in `inherited` (maybe your patch preserves this too?) Provided both *internal* inheritance and constant assignment have happened, we are discussing the order in which the user-facing callbacks are invoked. As the description says, in `const_added`, today inheritance already happened (the value has a superclass), but note that the `inherited` callback was not fired. This is not inconsistent if we consider internal operations to be decouple from the public hooks. On the other hand, in `inherited`, the constant was already assigned (`const_get` gives it to you and the subclass has a permanent name). I am fine either way, though reordering would make me document in Zeitwerk that you cannot refer to certain constants in `inherited` hooks. Sometimes, the need to write such docs is a signal that the feature is not quite right. So, fine either way, but slightly slanted towards keeping things as they are and applying my doc + specs patch :). ---------------------------------------- Misc #21143: Speficy order of execution const_added vs inherited https://bugs.ruby-lang.org/issues/21143#change-112312 * Author: fxn (Xavier Noria) * Status: Feedback ---------------------------------------- The hooks `const_added` and `inherited` may need to be executed "together". For example, consider: ```ruby module M def self.const_added(cname) = ... class C def self.inherited(subclass) = ... end class D < C; end end ``` When `D` is defined, two hooks are set to run, but in which order? Both orders make sense in a way: 1. When `inherited` is called, you can observe that the subclass has a permanent name, ergo it was assigned to a constant, which must me stored in a class or module object. Therefore, the constant was added to said class/module before `inherited` was invoked. 1. When `const_added` is called, you can `const_get` the symbol and observe the object is a class, hence with a superclass, hence inheritance already happened. The patch in [ruby#12759](https://github.com/ruby/ruby/pull/12759) documents and adds a test for (1). Rationale: 1. I believe it would be nice to specify this order. 1. Chose (1) because it is how it works today. While the motivation for the patch was formal (to remove an ambiguity), after reflecting about this I realized users of Zeitwerk may depend on this. Nowadays, Zeitwerk uses `const_added` to set autoloads for child constants in namespaces. Thanks to the current order, code can be used in `inherited` hooks normally (it would not be ready if the order was different). -- https://bugs.ruby-lang.org/

Issue #21143 has been updated by Eregon (Benoit Daloze). @byroot 's PR swaps `rb_class_inherited()` and `rb_const_set()`, so AFAIK the constant is not set yet in the "lexical parent/namespace" module when `inherited` is called. It's kind of nice to keep "actual constant assignment" and "calling const_added" together, and also it's consistent with `C = Class.new(parent)` where it happens in the same order as in that PR. I'm just not sure if it might cause compatibility issues, but I suggest to try, we are early in the dev cycle and can always revert if it causes problems. ---------------------------------------- Misc #21143: Speficy order of execution const_added vs inherited https://bugs.ruby-lang.org/issues/21143#change-112317 * Author: fxn (Xavier Noria) * Status: Feedback ---------------------------------------- The hooks `const_added` and `inherited` may need to be executed "together". For example, consider: ```ruby module M def self.const_added(cname) = ... class C def self.inherited(subclass) = ... end class D < C; end end ``` When `D` is defined, two hooks are set to run, but in which order? Both orders make sense in a way: 1. When `inherited` is called, you can observe that the subclass has a permanent name, ergo it was assigned to a constant, which must me stored in a class or module object. Therefore, the constant was added to said class/module before `inherited` was invoked. 1. When `const_added` is called, you can `const_get` the symbol and observe the object is a class, hence with a superclass, hence inheritance already happened. The patch in [ruby#12759](https://github.com/ruby/ruby/pull/12759) documents and adds a test for (1). Rationale: 1. I believe it would be nice to specify this order. 1. Chose (1) because it is how it works today. While the motivation for the patch was formal (to remove an ambiguity), after reflecting about this I realized users of Zeitwerk may depend on this. Nowadays, Zeitwerk uses `const_added` to set autoloads for child constants in namespaces. Thanks to the current order, code can be used in `inherited` hooks normally (it would not be ready if the order was different). -- https://bugs.ruby-lang.org/

Issue #21143 has been updated by fxn (Xavier Noria). The problem with `C = Class.new(parent)` is that it is a totally different mindset. In the thing we are discussing, the interpreter is in charge. In the other example, the user has decided to decouple both things. That anonymous class could be stored in a variable, passed three frames up and down, and perhaps be assigned to a constant 10 minutes later. Or never. That is, in my mind instantiating an anonymous class object totally decouples the callbacks in a way that is expected. Furthermore, if you have an autoload for `:C`: ```ruby autoload :C, 'x' ``` `const_added` is going to be called before `inherited` anyway (because it is triggered by the `autoload` call itself). Analogous situation in my view, the user decided to decouple the actions. ---------------------------------------- Misc #21143: Speficy order of execution const_added vs inherited https://bugs.ruby-lang.org/issues/21143#change-112323 * Author: fxn (Xavier Noria) * Status: Feedback ---------------------------------------- The hooks `const_added` and `inherited` may need to be executed "together". For example, consider: ```ruby module M def self.const_added(cname) = ... class C def self.inherited(subclass) = ... end class D < C; end end ``` When `D` is defined, two hooks are set to run, but in which order? Both orders make sense in a way: 1. When `inherited` is called, you can observe that the subclass has a permanent name, ergo it was assigned to a constant, which must me stored in a class or module object. Therefore, the constant was added to said class/module before `inherited` was invoked. 1. When `const_added` is called, you can `const_get` the symbol and observe the object is a class, hence with a superclass, hence inheritance already happened. The patch in [ruby#12759](https://github.com/ruby/ruby/pull/12759) documents and adds a test for (1). Rationale: 1. I believe it would be nice to specify this order. 1. Chose (1) because it is how it works today. While the motivation for the patch was formal (to remove an ambiguity), after reflecting about this I realized users of Zeitwerk may depend on this. Nowadays, Zeitwerk uses `const_added` to set autoloads for child constants in namespaces. Thanks to the current order, code can be used in `inherited` hooks normally (it would not be ready if the order was different). -- https://bugs.ruby-lang.org/