Keystrokes between `debugger` sessions seem to persist

[joshuay03]

Your environment

• ruby -v: ruby 3.2.2 (2023-03-30 revision e51014f9c0) [arm64-darwin22]
• rdbg -v: rdbg 1.9.2

Describe the bug

After hitting a debugger break point once, and using c to move on, if you hit Enter before the next break point, the next breakpoint is skipped.

To Reproduce

Script:

require "debug"; def my_method; 2.times { |i| p i; debugger; sleep 1 }; end

Without hitting Enter:

1.mov

With hitting Enter during the first sleep:

2.mov

Expected behavior

The execution should stop at the next breakpoint regardless of what keystrokes are used between breakpoints.

Additional context

None.

[ko1]

wow I see... Should we consume all input before REPL?

[ko1]

advices are very welcome If someone knows a techniques about it on other implementations

[joshuay03]

Should we consume all input before REPL?

Hmm possibly, is that considered unconventional? Might be worth looking at how pry handles this.

Or maybe just ignore previous REPL if in-between sessions.

[joshuay03]

The source of the issue:

debug/lib/debug/session.rb

Lines 1146 to 1152 in 0b77e82

	if line.empty?
	if @repl_prev_line
	line = @repl_prev_line
	else
	return :retry
	end
	else

[mattkuras]

I too recently encountered this same issue. makes it hard to clear extra lines in the console

[dhh]

Been seeing the same issue. This didn't use to be the case. Maybe we can track down when this started?

[joshuay03]

Maybe we can track down when this started?

I think it was introduced here. And there's this related follow-up issue.

I think a sensible middle ground would be to skip the repeat functionality on enter / empty line until the prompt is displaying. Or discard empty line input altogether until then.

[dhh]

@ko1 What do you think about an option where Rails could turn off this repeater behavior? Right now ruby/debug is not all that usable in Rails because of this issue.

[ko1]

Sorry for long absent.

I have two options.

1. clear $stdin just before printing prompt.
2. provide an option to disable repeating input.

I made patches for 1 and 2. 1 seems aggressive, but I'll try to merge.
2 is conservative approach, so no problem to introduce (RUBY_DEBUG_NO_REPEAT or no_repeat option).

BTW, I confirmed that:

a. pry behaves similar (typed "foo" while sleeping appears on the prompt) , but pry doesn't have repeating previous command with white space, there is no same issue.
b. gdb behaves similar and has same issue.

[ko1]

For 1, I found that the patch makes failure on remote debugging features.

[joshuay03]

Thank you @ko1, it seems we can close this issue off in that case?

@dhh I opened rails/rails#55214 if we want to enable the config option in new Rails apps.