Cache hash value of Sexps

for faster lookups

lib/brakeman/util.rb

@@ -187,20 +187,3 @@ module Brakeman::Util
     exp.is_a? Sexp
   end
 end
-
-class Sexp
-  alias :old_init :initialize
-
-  def initialize *args
-    old_init *args
-    @original_line = nil
-  end
-
-  def original_line line = nil
-    if line
-      @original_line = line
-    else
-      @original_line
-    end
-  end
-end

lib/ruby_parser/ruby_parser_extras.rb

@@ -1052,7 +1052,7 @@ class Symbol
 end
 
 class Sexp
-  attr_writer :paren
+  attr_reader :paren
 
   def paren
     @paren ||= false
@@ -1069,6 +1069,94 @@ class Sexp
 
   alias :node_type :sexp_type
   alias :values :sexp_body # TODO: retire
+
+  alias :old_init :initialize
+  alias :old_push :<<
+  alias :old_line :line
+  alias :old_line_set :line=
+  alias :old_file_set :file=
+  alias :old_comments_set :comments=
+  alias :old_compact :compact
+  alias :old_fara :find_and_replace_all
+  alias :old_find_node :find_node
+
+  def initialize *args
+    old_init *args
+    @original_line = nil
+    @my_hash_value = nil
+  end
+
+  def original_line line = nil
+    if line
+      @my_hash_value = nil
+      @original_line = line
+    else
+      @original_line
+    end
+  end
+
+  def hash
+    #There still seems to be some instances in which the hash of the
+    #Sexp changes, but I have not found what method call is doing it.
+    #Of course, Sexp is subclasses from Array, so who knows what might
+    #be going on.
+    @my_hash_value ||= super
+  end
+
+  def line *args
+    @my_hash_value = nil
+    old_line *args
+  end
+
+  def line= *args
+    @my_hash_value = nil
+    old_line_set *args
+  end
+
+  def file= *args
+    @my_hash_value = nil
+    old_file_set *args
+  end
+
+  def compact
+    @my_hash_value = nil
+    old_compact *args
+  end
+
+  def find_and_replace_all *args
+    @my_hash_value = nil
+    old_fara *args
+  end
+
+  def find_node *args
+    @my_hash_value = nil
+    old_find_node *args
+  end
+
+  def paren= arg
+    @my_hash_value = nil
+    @paren = arg
+  end
+
+  def comments= *args
+    @my_hash_value = nil
+    old_comments_set *args
+  end
+end
+
+#Invalidate hash cache if the Sexp changes
+[:[]=, :clear, :collect!, :compact!, :concat, :delete, :delete_at,
+  :delete_if, :drop, :drop_while, :fill, :flatten!, :replace, :insert,
+  :keep_if, :map!, :pop, :push, :reject!, :replace, :reverse!, :rotate!,
+  :select!, :shift, :shuffle!, :slice!, :sort!, :sort_by!, :transpose, 
+  :uniq!, :unshift].each do |method|
+
+  Sexp.class_eval <<-RUBY
+    def #{method} *args
+      @my_hash_value = nil
+      super
+    end
+    RUBY
 end
 
 # END HACK