After entering debug, _ (underscore) stops working

[joe-sharp]

Description

Underscore stops working correctly after entering debug mode. Issue is present on Ruby 2.7.8-3.3.0. Cross filed from ruby/debug#1069

Additional context

Shell session:

irb(#<RuboCop::Formatter::Markdow...):001> 3+3
=> 6
irb(#<RuboCop::Formatter::Markdow...):002> _
=> 6
irb(#<RuboCop::Formatter::Markdow...):003> debug
irb:rdbg(#<RuboCop::Formatter::Markdow...):002> 3+3
6
irb:rdbg(#<RuboCop::Formatter::Markdow...):003> _
nil

This older more detailed shell session shows that the most recent irb error seems to be returned if it were the last command.

Older Shell session:

irb(#<Foobar:0x000000011efeb9f0>):001> 3+3
=> 6

irb(#<Foobar:0x000000011efeb9f0>):002> puts _
6
=> nil

irb(#<Foobar:0x000000011efeb9f0>):003> 4+4
=> 8

irb(#<Foobar:0x000000011efeb9f0>):004> info
(rdbg:irb) info
%self = #<Foobar:0x000000011efeb9f0 @foo="bar">
@foo = "bar"

irb:rdbg(#<Foobar:0x000000011efeb9f0>):002> puts _

nil

irb:rdbg(#<Foobar:0x000000011efeb9f0>):003> 4+4
8

irb:rdbg(#<Foobar:0x000000011efeb9f0>):004> puts _

nil
irb:rdbg(#<Foobar:0x000000011efeb9f0>):005> 4+4
8

irb:rdbg(#<Foobar:0x000000011efeb9f0>):006> info
%self = #<Foobar:0x000000011efeb9f0 @foo="bar">
_ = nil
@foo = "bar"

irb:rdbg(#<Foobar:0x000000011efeb9f0>):007> ls Bar
Traceback (most recent call last):
	24: from /Users/joesharp/.asdf/installs/ruby/2.7.8/lib/ruby/gems/2.7.0/gems/debug-1.9.1/lib/debug/session.rb:212:in `block in activate'
	23: from /Users/joesharp/.asdf/installs/ruby/2.7.8/lib/ruby/gems/2.7.0/gems/debug-1.9.1/lib/debug/session.rb:254:in `session_server_main'
	22: from /Users/joesharp/.asdf/installs/ruby/2.7.8/lib/ruby/gems/2.7.0/gems/debug-1.9.1/lib/debug/session.rb:365:in `process_event'
	21: from /Users/joesharp/.asdf/installs/ruby/2.7.8/lib/ruby/gems/2.7.0/gems/debug-1.9.1/lib/debug/session.rb:403:in `wait_command_loop'
	20: from /Users/joesharp/.asdf/installs/ruby/2.7.8/lib/ruby/gems/2.7.0/gems/debug-1.9.1/lib/debug/session.rb:403:in `loop'
	19: from /Users/joesharp/.asdf/installs/ruby/2.7.8/lib/ruby/gems/2.7.0/gems/debug-1.9.1/lib/debug/session.rb:404:in `block in wait_command_loop'
	18: from /Users/joesharp/.asdf/installs/ruby/2.7.8/lib/ruby/gems/2.7.0/gems/debug-1.9.1/lib/debug/session.rb:444:in `wait_command'
	15: from /Users/joesharp/.asdf/installs/ruby/2.7.8/lib/ruby/gems/2.7.0/gems/debug-1.9.1/lib/debug/session.rb:1981:in `intercept_trap_sigint'
	 4: from /Users/joesharp/.asdf/installs/ruby/2.7.8/lib/ruby/gems/2.7.0/gems/debug-1.9.1/lib/debug/irb_integration.rb:9:in `evaluate'
(irb):7:in `set_foo': uninitialized constant Foobar::Bar (NameError)`

irb:rdbg(#<Foobar:0x000000011efeb9f0>):008> puts _
uninitialized constant Foobar::Bar
nil

irb:rdbg(#<Foobar:0x000000011efeb9f0>):009> ls Bar
Traceback (most recent call last):
	24: from /Users/joesharp/.asdf/installs/ruby/2.7.8/lib/ruby/gems/2.7.0/gems/debug-1.9.1/lib/debug/session.rb:212:in `block in activate'
	23: from /Users/joesharp/.asdf/installs/ruby/2.7.8/lib/ruby/gems/2.7.0/gems/debug-1.9.1/lib/debug/session.rb:254:in `session_server_main'
	22: from /Users/joesharp/.asdf/installs/ruby/2.7.8/lib/ruby/gems/2.7.0/gems/debug-1.9.1/lib/debug/session.rb:365:in `process_event'
	21: from /Users/joesharp/.asdf/installs/ruby/2.7.8/lib/ruby/gems/2.7.0/gems/debug-1.9.1/lib/debug/session.rb:403:in `wait_command_loop'
	20: from /Users/joesharp/.asdf/installs/ruby/2.7.8/lib/ruby/gems/2.7.0/gems/debug-1.9.1/lib/debug/session.rb:403:in `loop'
	19: from /Users/joesharp/.asdf/installs/ruby/2.7.8/lib/ruby/gems/2.7.0/gems/debug-1.9.1/lib/debug/session.rb:404:in `block in wait_command_loop'
	18: from /Users/joesharp/.asdf/installs/ruby/2.7.8/lib/ruby/gems/2.7.0/gems/debug-1.9.1/lib/debug/session.rb:444:in `wait_command'
	15: from /Users/joesharp/.asdf/installs/ruby/2.7.8/lib/ruby/gems/2.7.0/gems/debug-1.9.1/lib/debug/session.rb:1981:in `intercept_trap_sigint'
	 4: from /Users/joesharp/.asdf/installs/ruby/2.7.8/lib/ruby/gems/2.7.0/gems/debug-1.9.1/lib/debug/irb_integration.rb:9:in `evaluate'
(irb):9:in `set_foo': uninitialized constant Foobar::Bar (NameError)`

irb:rdbg(#<Foobar:0x000000011efeb9f0>):010> info
%self = #<Foobar:0x000000011efeb9f0 @foo="bar">
_ = #<NameError: uninitialized constant Foobar::Bar>
@foo = "bar"

irb:rdbg(#<Foobar:0x000000011efeb9f0>):011> Bar.methods
eval error: uninitialized constant Foobar::Bar
  (rdbg)/scratch.rb:1:in `set_foo'`
nil

irb:rdbg(#<Foobar:0x000000011efeb9f0>):012> info
%self = #<Foobar:0x000000011efeb9f0 @foo="bar">
_ = nil
@foo = "bar"

irb:rdbg(#<Foobar:0x000000011efeb9f0>):013> Bar.methods
eval error: uninitialized constant Foobar::Bar
  (rdbg)/scratch.rb:1:in `set_foo'`
nil

irb:rdbg(#<Foobar:0x000000011efeb9f0>):014> puts _

nil

Result of irb_info

Please paste the result of irb_info command in IRB.

ex.)

irb:rdbg(#<RuboCop::Formatter::Markdow...):004> irb_info
Ruby version: 3.2.3
IRB version: irb 1.11.2 (2024-02-07)
InputMethod: RelineInputMethod with Reline 0.4.3
Completion: Autocomplete, RegexpCompletor
.irbrc path: /Users/joesharp/.config/irb/irbrc
RUBY_PLATFORM: arm64-darwin22
LANG env: en_US.UTF-8
East Asian Ambiguous Width: 1

Terminal Emulator

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iTerm2

Setting Files

Are you using ~/.irbrc and ~/.inputrc?
Only an irbrc