Page the output in irb:rdbg sessions too

[st0012]

IRB started to page its evaluation output and it became a useful feature for users. However, in irb:rdbg sessions, the output is not paged so the sudden change in behavior is surprising and inconvenient.

This commit makes irb:rdbg sessions page the output of the debugger too.

Notes:

• I didn't add a test for it as we currently don't have a way to test pager output.
• When printing results from ThreadClient, Debug::UI#puts will always receive string. So we only need to activate pager in that case. In fact, debug most of the time passes string to this method, except for when printing exception backtrace.

[tompng]

This input will launch the pager 3 times.

irb:rdbg(main):025> outline Object.new.tap{|o|['a','b','c'].each{o.define_singleton_method(_1*10000){}}}

This part calls Debug::UI#puts several times to print a single output.
https://github.com/ruby/debug/blob/9c4279598e9e0376657b3813bf76a206f1f97beb/lib/debug/session.rb#L278C7-L278C13

# in DEBUGGER__::Session#process_event
output.each{|str| @ui.puts str} if ev != :suspend

I think this is just an acceptable edge case. Maybe we can fix it in debug.
What do you think?

[st0012]

Thanks for catching that. Since outline is just a ported version of ls (ruby/debug#173), an alternative could be that we somehow alias outline to IRB's ls command in irb:rdbg mode 🤔

[st0012]

an alternative could be that we somehow alias outline to IRB's ls command in irb:rdbg mode

Actually not cause we need to have an outline command class for that to work. And I don't think it's worth introducing a new command (even just as an alias) just to work around this edge case. I'll submit a PR to debug if people does hit this case.

[technicalpickles]

Thanks for fixing this! I asked about this on the ruby-dx slack and was not effecting a solution this fast for it 😁