[ruby/irb] Support repeating debugger input by passing empty input

to it
(https://github.com/ruby/irb/pull/856)

* Test IRB's behaviour with empty input

* Handle empty input and pass it to debugger

Since `rdbg` accepts empty input to repeat the previous command, IRB
should take empty input in `irb:rdbg` sessions and pass them to the
debugger.

Currently, IRB simply ignores empty input and does nothing. This commit
creates `EmptyInput` to represent empty input so it can fit into the
current IRB's input processing flow in `Irb#eval_input`.

https://github.com/ruby/irb/commit/0e9db419be

1 files changed, 5 insertions, 4 deletions

diff --git a/lib/irb.rb b/lib/irb.rb
index 67e03f8bc9..fd06626e9b 100644
--- a/lib/irb.rb
+++ b/lib/irb.rb
@@ -1082,16 +1082,17 @@ module IRB
       loop do
         code = readmultiline
         break unless code
-
-        if code != "\n"
-          yield build_statement(code), @line_no
-        end
+        yield build_statement(code), @line_no
         @line_no += code.count("\n")
       rescue RubyLex::TerminateLineInput
       end
     end
 
     def build_statement(code)
+      if code.match?(/\A\n*\z/)
+        return Statement::EmptyInput.new
+      end
+
       code.force_encoding(@context.io.encoding)
       command_or_alias, arg = code.split(/\s/, 2)
       # Transform a non-identifier alias (@, $) or keywords (next, break)