From: "Eregon (Benoit Daloze) via ruby-core" <ruby-core@...>
Date: 2025-04-26T18:25:11+00:00
Subject: [ruby-core:121738] [Ruby Bug#21272] Class.new doesn't trigger :class TracePoint

Issue #21272 has been updated by Eregon (Benoit Daloze).


In my view, `Baz = Class.new` doesn't really "Start a class or module definition." it creates a class but there is no definition of it, no body.
Though `Baz = Class.new { ... }` would arguably start a definition/body, but then so would `Baz.class_exec { ... }` and that seems less reasonable to catch with a :class TracePoint.

I think unless there is a good motivating example to change behavior (which could be incompatible), it's better to just document it better, so I'd suggest opening a PR to document it better.

----------------------------------------
Bug #21272: Class.new doesn't trigger :class TracePoint
https://bugs.ruby-lang.org/issues/21272#change-112793

* Author: st0012 (Stan Lo)
* Status: Open
* Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
----------------------------------------
According to the official [documentation](https://docs.ruby-lang.org/en/master/TracePoint.html#class-TracePoint-label-Events):

> To filter what is traced, you can pass any of the following as events:
> 
> :class
> Start a class or module definition.

I'd expect `:class` events to be triggered when new classes are defined via `Class.new` as well, but currently that's not the case.

Should we either support `Class.new`, or clarify the behaviour in documentation?

### Reproduction

```rb
TracePoint.trace(:class) do |tp|
  puts "Class created at line: #{tp.lineno}"
end

class Foo; end # Triggers the tracepoint

Baz = Class.new # Doesn't trigger the tracepoint

# ruby test.rb
# Class created at line: 5
```




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