Finally figured it out: properly intercept Array#grep

lib/ap/core_ext/array.rb

@@ -3,18 +3,18 @@
 # Awesome Print is freely distributable under the terms of MIT license.
 # See LICENSE file or http://www.opensource.org/licenses/mit-license.php
 #------------------------------------------------------------------------------
+#
+# The following makes it possible to invoke awesome_print while performing
+# operations on method arrays, ex:
+#
+#   ap [].methods - Object.methods
+#   ap ''.methods.grep(/!|\?/)
+#
+# If you could think of a better way please let me know: twitter.com/mid :-)
+#
 class Array
-  #
-  # The following makes it possible to invoke awesome_print while performing
-  # operations on method arrays, ex:
-  # 
-  #   ap [].methods - Object.methods
-  #   ap ''.methods.grep(/!|\?/)
-  # 
-  # If you could think of a better way please let me know: twitter.com/mid :-)
-  #
   [ :-, :& ].each do |operator|
-    alias_method :"original_#{operator.object_id}", operator
+    alias :"original_#{operator.object_id}" :"#{operator}"
     define_method operator do |*args|
       arr = self.send(:"original_#{operator.object_id}", *args)
       if self.instance_variable_defined?('@__awesome_methods__')
@@ -24,10 +24,40 @@ class Array
       arr
     end
   end
-
-  alias_method :original_grep, :grep
-  define_method :grep do |*args, &blk|
-    arr = original_grep(*args, &blk)
+  #
+  # Intercepting Array#grep needs a special treatment since grep accepts
+  # an optional block.
+  #
+  alias :original_grep :grep
+  def grep(pattern, &blk)
+    #
+    # The following looks rather insane and I've sent numerous hours trying
+    # to figure it out. The problem is that if grep gets called with the
+    # block, for example:
+    #
+    #    [].methods.grep(/(.+?)_by/) { $1.to_sym }
+    #
+    # ...then simple:
+    #
+    #    original_grep(pattern, &blk)
+    #
+    # doesn't set $1 within the grep block which causes nil.to_sym failure.
+    # The workaround below has been tested with Ruby 1.8.7/Rails 2.3.8 and
+    # Ruby 1.9.2/Rails 3.0.0. For more info see the following thread dating
+    # back to 1993 when Ruby 1.8.0 was as fresh off the grill as Ruby 1.9.2
+    # is in 2010 :-)
+    #
+    # http://www.justskins.com/forums/bug-when-rerouting-string-52852.html
+    #
+    # BTW, if you figure out a better way of intercepting Array#grep please
+    # let me know: twitter.com/mid -- or just say hi so I know you've read
+    # the comment :-)
+    #
+    arr = unless blk
+      original_grep(pattern)
+    else
+      original_grep(pattern) { |match| eval("%Q/#{match}/ =~ #{pattern.inspect}", blk.binding); yield match }
+    end
     if self.instance_variable_defined?('@__awesome_methods__')
       arr.instance_variable_set('@__awesome_methods__', self.instance_variable_get('@__awesome_methods__'))
       arr.reject! { |item| !(item.is_a?(Symbol) || item.is_a?(String)) } # grep block might return crap.

spec/methods_spec.rb

@@ -384,4 +384,26 @@ describe "Methods arrays" do
     out = Hello.methods.grep(/^m\d$/).ai(:plain => true)
     out.should == "[\n    [0] m1() Hello\n    [1] m2() Hello\n    [2] m3() Hello\n]"
   end
+
+  it "obj1.methods.grep(pattern, &block) should pass the matching string within the block" do
+    class Hello
+      def self.m_one; end
+      def self.m_two; end
+    end
+
+    out = Hello.methods.grep(/^m_(.+)$/) { $1.to_sym }
+    out.should == [:one, :two]
+  end
+
+  it "obj1.methods.grep(pattern, &block) should be awesome printed" do
+    class Hello
+      def self.m0; end
+      def self.none; end
+      def self.m1; end
+      def self.one; end
+    end
+
+    out = Hello.methods.grep(/^m(\d)$/) { %w(none one)[$1.to_i] }.ai(:plain => true)
+    out.should == "[\n    [0] none() Hello\n    [1]  one() Hello\n]"
+  end
 end