forwardable.rb: backtrace

* lib/forwardable.rb (_delegator_method): leave the backtrace
  untouched during accessor.  forwardable.rb does not appear in
  the backtrace during delegated method because of tail-call
  optimization.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@55372 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,10 @@
+Sat Jun 11 09:31:28 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* lib/forwardable.rb (_delegator_method): leave the backtrace
+	  untouched during accessor.  forwardable.rb does not appear in
+	  the backtrace during delegated method because of tail-call
+	  optimization.
+
 Sat Jun 11 01:38:31 2016  Naohisa Goto  <ngotogenome@gmail.com>
 
 	* include/ruby/defines.h (GCC_VERSION_SINCE): Fix logic error by

lib/forwardable.rb

@@ -113,12 +113,9 @@ module Forwardable
   # Version of +forwardable.rb+
   FORWARDABLE_VERSION = "1.1.0"
 
-  FILE_REGEXP = %r"#{Regexp.quote(__FILE__)}"
-
   @debug = nil
   class << self
-    # If true, <tt>__FILE__</tt> will remain in the backtrace in the event an
-    # Exception is raised.
+    # ignored
     attr_accessor :debug
   end
 
@@ -204,8 +201,6 @@ module Forwardable
         def #{ali}(*args, &block)
           begin
             #{accessor}
-          ensure
-            $@.delete_if {|s| ::Forwardable::FILE_REGEXP =~ s} if $@ and !::Forwardable::debug
           end.__send__ :#{method}, *args, &block
         end
       end

test/test_forwardable.rb

@@ -225,18 +225,21 @@ class TestForwardable < Test::Unit::TestCase
   class Foo
     extend Forwardable
 
+    attr_accessor :bar
     def_delegator :bar, :baz
     def_delegator :caller, :itself, :c
-
-    class Exception
-    end
   end
 
   def test_backtrace_adjustment
+    obj = Foo.new
+    def (obj.bar = Object.new).baz
+      foo
+    end
     e = assert_raise(NameError) {
-      Foo.new.baz
+      obj.baz
     }
-    assert_not_match(/\/forwardable\.rb/, e.backtrace[0])
+    assert_not_match(/\/forwardable\.rb/, e.backtrace[0],
+                     proc {RubyVM::InstructionSequence.of(obj.method(:baz)).disassemble})
     assert_equal(caller(0, 1)[0], Foo.new.c[0])
   end