Make many parts of Rails lazy. In order to facilitate this,

add lazy_load_hooks.rb, which allows us to declare code that
should be run at some later time. For instance, this allows
us to defer requiring ActiveRecord::Base at boot time purely
to apply configuration. Instead, we register a hook that should
apply configuration once ActiveRecord::Base is loaded.

With these changes, brings down total boot time of a
new app to 300ms in production and 400ms in dev.

TODO: rename base_hook

9 files changed, 44 insertions, 101 deletions

diff --git a/activesupport/lib/active_support.rb b/activesupport/lib/active_support.rb
index ae31d191c0..e34e46b4cf 100644
--- a/activesupport/lib/active_support.rb
+++ b/activesupport/lib/active_support.rb
@@ -53,6 +53,7 @@ module ActiveSupport
     autoload :Deprecation
     autoload :Gzip
     autoload :Inflector
+    autoload :JSON
     autoload :Memoizable
     autoload :MessageEncryptor
     autoload :MessageVerifier
@@ -70,3 +71,5 @@ module ActiveSupport
   autoload :SafeBuffer, "active_support/core_ext/string/output_safety"
   autoload :TestCase
 end
+
+autoload :I18n, "active_support/i18n"
diff --git a/activesupport/lib/active_support/all.rb b/activesupport/lib/active_support/all.rb
index 64600575d9..f537818300 100644
--- a/activesupport/lib/active_support/all.rb
+++ b/activesupport/lib/active_support/all.rb
@@ -1,4 +1,3 @@
 require 'active_support'
-require 'active_support/i18n'
 require 'active_support/time'
 require 'active_support/core_ext'
diff --git a/activesupport/lib/active_support/core_ext/array/conversions.rb b/activesupport/lib/active_support/core_ext/array/conversions.rb
index 814567a5a6..2119322bfe 100644
--- a/activesupport/lib/active_support/core_ext/array/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/array/conversions.rb
@@ -1,7 +1,6 @@
 require 'active_support/core_ext/hash/keys'
 require 'active_support/core_ext/hash/reverse_merge'
 require 'active_support/inflector'
-require 'active_support/i18n'
 
 class Array
   # Converts the array to a comma-separated sentence where the last element is joined by the connector word. Options:
diff --git a/activesupport/lib/active_support/core_ext/string/interpolation.rb b/activesupport/lib/active_support/core_ext/string/interpolation.rb
index 06d3505c60..932117cc10 100644
--- a/activesupport/lib/active_support/core_ext/string/interpolation.rb
+++ b/activesupport/lib/active_support/core_ext/string/interpolation.rb
@@ -1,91 +1 @@
-=begin
-  heavily based on Masao Mutoh's gettext String interpolation extension
-  http://github.com/mutoh/gettext/blob/f6566738b981fe0952548c421042ad1e0cdfb31e/lib/gettext/core_ext/string.rb
-  Copyright (C) 2005-2010 Masao Mutoh
-  You may redistribute it and/or modify it under the same license terms as Ruby.
-=end
-
-if RUBY_VERSION < '1.9' && !"".respond_to?(:interpolate_without_ruby_19_syntax)
-
-  # KeyError is raised by String#% when the string contains a named placeholder
-  # that is not contained in the given arguments hash. Ruby 1.9 includes and
-  # raises this exception natively. We define it to mimic Ruby 1.9's behaviour
-  # in Ruby 1.8.x
-
-  class KeyError < IndexError
-    def initialize(message = nil)
-      super(message || "key not found")
-    end
-  end unless defined?(KeyError)
-
-  # Extension for String class. This feature is included in Ruby 1.9 or later but not occur TypeError.
-  #
-  # String#% method which accept "named argument". The translator can know
-  # the meaning of the msgids using "named argument" instead of %s/%d style.
-
-  class String
-    alias :interpolate_without_ruby_19_syntax :% # :nodoc:
-
-    INTERPOLATION_PATTERN = Regexp.union(
-      /%%/,
-      /%\{(\w+)\}/,                               # matches placeholders like "%{foo}"
-      /%<(\w+)>(.*?\d*\.?\d*[bBdiouxXeEfgGcps])/  # matches placeholders like "%<foo>.d"
-    )
-
-    # % uses self (i.e. the String) as a format specification and returns the
-    # result of applying it to the given arguments. In other words it interpolates
-    # the given arguments to the string according to the formats the string
-    # defines.
-    #
-    # There are three ways to use it:
-    #
-    # * Using a single argument or Array of arguments.
-    #
-    #   This is the default behaviour of the String class. See Kernel#sprintf for
-    #   more details about the format string.
-    #
-    #   Example:
-    #
-    #     "%d %s" % [1, "message"]
-    #     # => "1 message"
-    #
-    # * Using a Hash as an argument and unformatted, named placeholders.
-    #
-    #   When you pass a Hash as an argument and specify placeholders with %{foo}
-    #   it will interpret the hash values as named arguments.
-    #
-    #   Example:
-    #
-    #     "%{firstname}, %{lastname}" % {:firstname => "Masao", :lastname => "Mutoh"}
-    #     # => "Masao Mutoh"
-    #
-    # * Using a Hash as an argument and formatted, named placeholders.
-    #
-    #   When you pass a Hash as an argument and specify placeholders with %<foo>d
-    #   it will interpret the hash values as named arguments and format the value
-    #   according to the formatting instruction appended to the closing >.
-    #
-    #   Example:
-    #
-    #     "%<integer>d, %<float>.1f" % { :integer => 10, :float => 43.4 }
-    #     # => "10, 43.3"
-    def %(args)
-      if args.kind_of?(Hash)
-        dup.gsub(INTERPOLATION_PATTERN) do |match|
-          if match == '%%'
-            '%'
-          else
-            key = ($1 || $2).to_sym
-            raise KeyError unless args.has_key?(key)
-            $3 ? sprintf("%#{$3}", args[key]) : args[key]
-          end
-        end
-      elsif self =~ INTERPOLATION_PATTERN
-        raise ArgumentError.new('one hash required')
-      else
-        result = gsub(/%([{<])/, '%%\1')
-        result.send :'interpolate_without_ruby_19_syntax', args
-      end
-    end
-  end
-end
+require 'i18n/core_ext/string/interpolate'
diff --git a/activesupport/lib/active_support/dependencies/autoload.rb b/activesupport/lib/active_support/dependencies/autoload.rb
index 44edb89ad5..f669f4a77e 100644
--- a/activesupport/lib/active_support/dependencies/autoload.rb
+++ b/activesupport/lib/active_support/dependencies/autoload.rb
@@ -1,7 +1,12 @@
 require "active_support/inflector/methods"
+require "active_support/lazy_load_hooks"
 
 module ActiveSupport
   module Autoload
+    def self.extended(base)
+      base.extend(LazyLoadHooks)
+    end
+
     @@autoloads = {}
     @@under_path = nil
     @@at_path = nil
diff --git a/activesupport/lib/active_support/i18n.rb b/activesupport/lib/active_support/i18n.rb
index 854c60eec1..034d7d8ddc 100644
--- a/activesupport/lib/active_support/i18n.rb
+++ b/activesupport/lib/active_support/i18n.rb
@@ -1,2 +1,3 @@
 require 'i18n'
-I18n.load_path << "#{File.dirname(__FILE__)}/locale/en.yml"
\ No newline at end of file
+I18n.load_path << "#{File.dirname(__FILE__)}/locale/en.yml"
+ActiveSupport.run_base_hooks(:i18n)
\ No newline at end of file
diff --git a/activesupport/lib/active_support/lazy_load_hooks.rb b/activesupport/lib/active_support/lazy_load_hooks.rb
new file mode 100644
index 0000000000..36acfda524
--- /dev/null
+++ b/activesupport/lib/active_support/lazy_load_hooks.rb
@@ -0,0 +1,25 @@
+module ActiveSupport
+  module LazyLoadHooks
+    def _setup_base_hooks
+      @base_hooks ||= Hash.new {|h,k| h[k] = [] }
+      @base ||= {}
+    end
+
+    def base_hook(name = nil, &block)
+      _setup_base_hooks
+
+      if base = @base[name]
+        base.instance_eval(&block)
+      else
+        @base_hooks[name] << block
+      end
+    end
+
+    def run_base_hooks(base, name = nil)
+      _setup_base_hooks
+
+      @base_hooks[name].each { |hook| base.instance_eval(&hook) } if @base_hooks
+      @base[name] = base
+    end
+  end
+end
\ No newline at end of file
diff --git a/activesupport/lib/active_support/railtie.rb b/activesupport/lib/active_support/railtie.rb
index 58d11585ba..d2c13e030d 100644
--- a/activesupport/lib/active_support/railtie.rb
+++ b/activesupport/lib/active_support/railtie.rb
@@ -37,10 +37,12 @@ module I18n
     config.i18n.load_path = []
 
     initializer "i18n.initialize" do
-      require 'active_support/i18n'
-
-      ActionDispatch::Callbacks.to_prepare do
+      ActiveSupport.base_hook(:i18n) do
         I18n.reload!
+
+        ActionDispatch::Callbacks.to_prepare do
+          I18n.reload!
+        end
       end
     end
 
diff --git a/activesupport/lib/active_support/whiny_nil.rb b/activesupport/lib/active_support/whiny_nil.rb
index 0b68e936f6..91ddef2619 100644
--- a/activesupport/lib/active_support/whiny_nil.rb
+++ b/activesupport/lib/active_support/whiny_nil.rb
@@ -25,17 +25,16 @@
 # By default it is on in development and test modes, and it is off in production
 # mode.
 class NilClass
-  WHINERS = [::Array]
-  WHINERS << ::ActiveRecord::Base if defined? ::ActiveRecord::Base
-
   METHOD_CLASS_MAP = Hash.new
 
-  WHINERS.each do |klass|
+  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 }
   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 4 -- if you really wanted the id of nil, use object_id", caller