Fix Test timedout in test_debug_cmd

[tompng]

Description

In ruby head, readline-ext is removed. Readline.readline will be Reline.readline instead of readline.so.

The problem is that Reline prints "▽\e[6n", east-asian-amibuous character and device status report escape sequence.
Reline will wait for cursor position report \e[<row>;<col>R forever and cause timeout error.
Timeout result in #581
To suppress this, I override Reline::IOGate.cursor_pos to use Reline::GeneralIO.cursor_pos in test_debug_cmd

Failing test (help wanted)

Still one test is failing in ruby head.

Failed assertion

assert_match(/\(rdbg\) next/, output)

Actual output

From: /tmp/irb-20230516-1760-qqd7e7.rb @ line 1 :

 => 1: binding.irb
    2: puts "hello"

debug
next
continue
(rdbg) [1, 2] in /tmp/irb-20230516-1760-qqd7e7.rb
     1| binding.irb
=>   2| puts "hello"
=>#0	<main> at /tmp/irb-20230516-1760-qqd7e7.rb:2
(rdbg) hello

This is because ruby/debug is directly requiring readline.so and fallbacks to print prompt; gets.
https://github.com/ruby/debug/blob/4ec9d7ab46df09aa87d64e600df8805a3ee0314c/lib/debug/console.rb#L164-L168

[st0012]

@tompng I think if you also apply this change it'll pass:

diff --git a/test/irb/test_debug_cmd.rb b/test/irb/test_debug_cmd.rb
index 309e241..1cf6066 100644
--- a/test/irb/test_debug_cmd.rb
+++ b/test/irb/test_debug_cmd.rb
@@ -17,7 +17,7 @@ module TestIRB
 
   class DebugCommandTestCase < TestCase
     IRB_AND_DEBUGGER_OPTIONS = {
-      "RUBY_DEBUG_NO_RELINE" => "true", "NO_COLOR" => "true", "RUBY_DEBUG_HISTORY_FILE" => ''
+      "NO_COLOR" => "true", "RUBY_DEBUG_HISTORY_FILE" => ''
     }

A few questions:

1. What does this do?

   Reline prints "▽\e[6n", east-asian-amibuous character and device status report escape sequence.
   Reline will wait for cursor position report \e[;R forever and cause timeout error.

2. Should Reline.readline behave this way?

3. I found forcing Reline::IOGate to be GeneralIO also prevents the issue:

   @@ -214,11 +214,7 @@ module TestIRB
          rc_file.write(<<~RUBY)
            IRB.conf[:USE_SINGLELINE] = true
            require 'readline'
   -        if Readline.const_defined?(:IOGate)
   -          def (Reline::IOGate).cursor_pos
   -            Reline::GeneralIO.cursor_pos
   -          end
   -        end
   +        Reline.const_set(:IOGate, Reline::GeneralIO)
          RUBY
          rc_file.close

   If the answer of 2) is yes, perhaps we can make Reline's IOGate configurable so it works in testing environment too? ruby/debug could benefit from this.

[tompng]

What does this do?

It prints east asian ambiguous character, request current cursor position by printing "\e[6n", get the actual cursor position escape sequence from STDIN, and determine the actual east asian ambiguous character width.
User can set east asian ambiguous width to either half-width or full-width in preference panel of terminal emulator app. Reline should know this setting value.

Should Reline.readline behave this way?

I think yes. By doing it, reline can handle east asian ambiguous chars correctly.
On the other hand, readline does not do this. It assumes ambiguous char is half-width and it fails to render in full-width setting.

If STDIN and STDOUT is a TTY, reline is assuming it is run inside a terminal that answers to "\e[6n". I think this assumption is correct and what is wrong is that the test is using pty but does not act like a real terminal that reply to "\e[6n".

3. Reline::IOGate to be GeneralIO

Yes, it is one of the solution. Making configurable seems good.
We can also force reline to use GeneralIO by not using PTY.spawn but use IO.popen.
Unfortunately, I tried IO.popen but there was a problem of buffering.

IO.popen ['ruby', '-e', '5.times{sleep 1;puts _1}'], 'w+' do |io|
  5.times { puts io.gets }
  # expect: prints one line per sec for 5 times
  # actual: wait for 5 sec and prints 5 lines at once
  # It means, `line.match?(/binding\.irb/)` in test_debug_cmd will timeout.
end

[tompng]

Thanks for the diff, test passed!

[st0012]

Thanks for the fix and explanation 🙏
Yeah I think ideally we should:

• Either more realisticly simulate users’ activity in tests, which in this case means doing cursor position report (does this make sense though?)
• Or we should switch to popen

But we can do that in a follow up PR and let’s fix the build first 👍