Work around Readline clash

Only limited debugging functionality is available to things that involve
the Readline formula, but it is better than crashing outright.

c.f. Homebrew/homebrew#15776.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>

1 files changed, 8 insertions, 7 deletions

diff --git a/Library/Homebrew/debrew.rb b/Library/Homebrew/debrew.rb
index eff396909..54f01a234 100644
--- a/Library/Homebrew/debrew.rb
+++ b/Library/Homebrew/debrew.rb
@@ -1,9 +1,10 @@
-require 'irb'
-begin
-  require 'continuation' # needed on 1.9
-rescue LoadError
+def can_use_readline?
+  not ENV['HOMEBREW_NO_READLINE']
 end
 
+require 'irb' if can_use_readline?
+require 'continuation' if RUBY_VERSION.to_f >= 1.9
+
 class Menu
   attr_accessor :prompt
   attr_accessor :entries
@@ -75,7 +76,7 @@ module IRB
       irb_at_exit
     end
   end
-end
+end if can_use_readline?
 
 class Exception
   attr_accessor :continuation
@@ -92,7 +93,7 @@ def has_debugger?
     true
   rescue LoadError
     false
-  end
+  end if can_use_readline?
 end
 
 def debrew(exception, formula=nil)
@@ -121,7 +122,7 @@ def debrew(exception, formula=nil)
             end
           }
         end
-      end
+      end if can_use_readline?
       menu.choice(:shell) do
         puts "When you exit this shell, you will return to the menu."
         interactive_shell formula