[ruby-core:109934] [Ruby master Bug#19003] TracePoint behavior inconsistency in 3.2.0-preview2

Issue #19003 has been updated by hurricup (Alexandr Evstigneev).


jeremyevans0 (Jeremy Evans) wrote in #note-2:

I just saying this behavior is inconsistent between versions.

Current behavior looks like a bug to me, because it feels like only hooks already set at the moment of the event arrival should handle it, not ones set while processing the event by another hook.

If API user need some additional actions to be performed on the current event, he can achieve that by additional logic in the hook. I can't imagine any case where current ruby behavior may be beneficial in any way. And from other side it's unintuitive and confusing. 

And scope of the hook (local/global) should not affect behavior in any way. This should be implementation details without any guaranteed order or behavior specifics. 

For API user it's just a TracePoint, with or without constructor arguments. 


----------------------------------------
Bug #19003: TracePoint behavior inconsistency in 3.2.0-preview2
https://bugs.ruby-lang.org/issues/19003#change-99181

* Author: hurricup (Alexandr Evstigneev)
* Status: Open
* Priority: Normal
* ruby -v: ruby 3.2.0preview2 (2022-09-09 master 35cfc9a3bb) [x86_64-linux]
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
This is kind of continuation of my previous report about global/local TP processing (#18730).

Sample script:
```rb
def foo
  return 1
end

puts RubyVM::InstructionSequence.of(method :foo).disasm

def step_over
  TracePoint.new(:line, :return, :b_return) do |tp|
    puts "Step over hits by #{tp.event} at #{tp.lineno}"
    step_over
    tp.disable
  end.enable(target: RubyVM::InstructionSequence.of(method :foo), target_thread: Thread.current)
end

TracePoint.new(:line, :return, :b_return) do |tp|
  if tp.lineno == 2
    puts "Step into hits by #{tp.event} at #{tp.lineno}"
    step_over
    tp.disable
  end
end.enable(target_thread: Thread.current)

a = foo
```

In ruby 3.1.2 we have expected behavior. Output:
```
== disasm: #<ISeq:foo@/home/hurricup/Projects/ruby-debugger/jb-debase-30/test_sample.rb:1 (1,0)-(3,3)> (catch: FALSE)
0000 putobject_INT2FIX_1_                                             (   2)[LiCa]
0001 leave                                                            (   3)[Re]
Step into hits by line at 2
Step over hits by return at 3
```

In ruby 3.2.0-preview2 - not so much. Output:
```
== disasm: #<ISeq:foo@/home/hurricup/Projects/ruby-debugger/jb-debase-30/test_sample.rb:1 (1,0)-(3,3)> (catch: false)
0000 putobject_INT2FIX_1_                                             (   2)[LiCa]
0001 leave                                                            (   3)[Re]
Step into hits by line at 2
Step over hits by line at 2
Step over hits by return at 3
```



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