[ruby/irb] Support seamless integration with ruby/debug

(https://github.com/ruby/irb/pull/575)

* Support native integration with ruby/debug

* Prevent using multi-irb and activating debugger at the same time

Multi-irb makes a few assumptions:

- IRB will manage all threads that host sub-irb sessions
- All IRB sessions will be run on the threads created by IRB itself

However, when using the debugger these assumptions are broken:

- `debug` will freeze ALL threads when it suspends the session (e.g. when
  hitting a breakpoint, or performing step-debugging).
- Since the irb-debug integration runs IRB as the debugger's interface,
  it will be run on the debugger's thread, which is not managed by IRB.

So we should prevent the 2 features from being used at the same time.
To do that, we check if the other feature is already activated when
executing the commands that would activate the other feature.

https://github.com/ruby/irb/commit/d8fb3246be

1 files changed, 5 insertions, 1 deletions

diff --git a/lib/irb/ruby-lex.rb b/lib/irb/ruby-lex.rb
index 7d4f8a514c..282e6ef05f 100644
--- a/lib/irb/ruby-lex.rb
+++ b/lib/irb/ruby-lex.rb
@@ -183,6 +183,10 @@ class RubyLex
     prompt(opens, continue, line_num_offset)
   end
 
+  def increase_line_no(addition)
+    @line_no += addition
+  end
+
   def readmultiline
     save_prompt_to_context_io([], false, 0)
 
@@ -220,7 +224,7 @@ class RubyLex
         code.force_encoding(@context.io.encoding)
         yield code, @line_no, assignment_expression?(code)
       end
-      @line_no += code.count("\n")
+      increase_line_no(code.count("\n"))
     rescue TerminateLineInput
     end
   end