From d1abf29e796a86cbac315da217f3fe7addb88106 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jos=C3=A9=20Valim?= <jose.valim@gmail.com>
Date: Thu, 8 Dec 2011 20:21:48 +0100
Subject: Remove NilClass whiners feature.

Removing this feature causes boost in performance when using Ruby 1.9.

Ruby 1.9 started to do implicit conversions using `to_ary` and `to_str`
in some STDLIB methods (like Array#join). To do such implicit conversions,
Ruby 1.9 always dispatches the method and rescues the NoMethodError exception
in case one is raised.

Therefore, since the whiners feature defined NilClass#method_missing, such
implicit conversions for nil became much, much slower. In fact, just defining
NilClass#method_missing (even without the whiners feature) already causes a
massive slow down. Here is a snippet that shows such slow down:

    require "benchmark"
    Benchmark.realtime { 1_000.times { [nil,nil,nil].join } }

    class NilClass
      def method_missing(*args)
        raise NoMethodError
      end
    end

    Benchmark.realtime { 1_000.times { [nil,nil,nil].join } }
---
 activesupport/lib/active_support/whiny_nil.rb | 42 ++-------------------------
 1 file changed, 2 insertions(+), 40 deletions(-)

(limited to 'activesupport/lib')

diff --git a/activesupport/lib/active_support/whiny_nil.rb b/activesupport/lib/active_support/whiny_nil.rb
index 577db5018e..a065233679 100644
--- a/activesupport/lib/active_support/whiny_nil.rb
+++ b/activesupport/lib/active_support/whiny_nil.rb
@@ -1,21 +1,6 @@
 # Extensions to +nil+ which allow for more helpful error messages for people who
 # are new to Rails.
 #
-# Ruby raises NoMethodError if you invoke a method on an object that does not
-# respond to it:
-#
-#   $ ruby -e nil.destroy
-#   -e:1: undefined method `destroy' for nil:NilClass (NoMethodError)
-#
-# With these extensions, if the method belongs to the public interface of the
-# classes in NilClass::WHINERS the error message suggests which could be the
-# actual intended class:
-#
-#   $ rails runner nil.destroy
-#   ...
-#   You might have expected an instance of ActiveRecord::Base.
-#   ...
-#
 # NilClass#id exists in Ruby 1.8 (though it is deprecated). Since +id+ is a fundamental
 # method of Active Record models NilClass#id is redefined as well to raise a RuntimeError
 # and warn the user. She probably wanted a model database identifier and the 4
@@ -25,36 +10,13 @@
 # By default it is on in development and test modes, and it is off in production
 # mode.
 class NilClass
-  METHOD_CLASS_MAP = Hash.new
-
   def self.add_whiner(klass)
-    methods = klass.public_instance_methods - public_instance_methods
-    class_name = klass.name
-    methods.each { |method| METHOD_CLASS_MAP[method.to_sym] = class_name }
+    ActiveSupport::Deprecation.warn "NilClass.add_whiner is deprecated and this functionality is " \
+      "removed from Rails versions as it affects Ruby 1.9 performance.", caller
   end
 
-  add_whiner ::Array
-
   # Raises a RuntimeError when you attempt to call +id+ on +nil+.
   def id
     raise RuntimeError, "Called id for nil, which would mistakenly be #{object_id} -- if you really wanted the id of nil, use object_id", caller
   end
-
-  private
-    def method_missing(method, *args)
-      if klass = METHOD_CLASS_MAP[method]
-        raise_nil_warning_for klass, method, caller
-      else
-        super
-      end
-    end
-
-    # Raises a NoMethodError when you attempt to call a method on +nil+.
-    def raise_nil_warning_for(class_name = nil, selector = nil, with_caller = nil)
-      message = "You have a nil object when you didn't expect it!"
-      message << "\nYou might have expected an instance of #{class_name}." if class_name
-      message << "\nThe error occurred while evaluating nil.#{selector}" if selector
-
-      raise NoMethodError, message, with_caller || caller
-    end
 end
-- 
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