Use autoload to delay loading features until we need them.

This yields about a 10% improvement in the time it
takes to initially load rspec-mocks.

benchmarks/boot_time.sh

@@ -0,0 +1,31 @@
+time (for i in {1..100}; do ruby -Ilib:../rspec-support/lib -rrspec/mocks -e ""; done)
+
+# 3 runs before our autoload changes
+# real  0m4.497s
+# user  0m3.662s
+# sys 0m0.677s
+#
+# real  0m4.472s
+# user  0m3.644s
+# sys 0m0.671s
+#
+# real  0m4.465s
+# user  0m3.640s
+# sys 0m0.668s
+
+# 3 runs after our autoload changes:
+#
+# real  0m4.038s
+# user  0m3.274s
+# sys 0m0.609s
+#
+# real  0m4.038s
+# user  0m3.274s
+# sys 0m0.609s
+#
+# real  0m4.038s
+# user  0m3.274s
+# sys 0m0.609s
+
+# It's modest, but that's about a 10% improvement: an average
+# of about 40ms to load rather than 45 ms to load.

lib/rspec/mocks.rb

@@ -14,19 +14,7 @@
 require 'rspec/mocks/error_generator'
 require 'rspec/mocks/space'
 require 'rspec/mocks/extensions/marshal'
-require 'rspec/mocks/any_instance/chain'
-require 'rspec/mocks/any_instance/stub_chain'
-require 'rspec/mocks/any_instance/stub_chain_chain'
-require 'rspec/mocks/any_instance/expect_chain_chain'
-require 'rspec/mocks/any_instance/expectation_chain'
-require 'rspec/mocks/any_instance/message_chains'
-require 'rspec/mocks/any_instance/recorder'
 require 'rspec/mocks/mutate_const'
-require 'rspec/mocks/matchers/have_received'
-require 'rspec/mocks/matchers/receive'
-require 'rspec/mocks/matchers/receive_messages'
-require 'rspec/mocks/matchers/receive_message_chain'
-require 'rspec/mocks/message_chain'
 require 'rspec/mocks/targets'
 require 'rspec/mocks/syntax'
 require 'rspec/mocks/configuration'
@@ -114,5 +102,18 @@ class << self; attr_reader :space; end
 
     # @private
     IGNORED_BACKTRACE_LINE = 'this backtrace line is ignored'
+
+    # To speed up boot time a bit, delay loading optional or rarely
+    # used features until their first use.
+    autoload :AnyInstance, "rspec/mocks/any_instance"
+    autoload :ExpectChain, "rspec/mocks/message_chain"
+    autoload :StubChain,   "rspec/mocks/message_chain"
+
+    module Matchers
+      autoload :HaveReceived,        "rspec/mocks/matchers/have_received"
+      autoload :Receive,             "rspec/mocks/matchers/receive"
+      autoload :ReceiveMessageChain, "rspec/mocks/matchers/receive_message_chain"
+      autoload :ReceiveMessages,     "rspec/mocks/matchers/receive_messages"
+    end
   end
 end

lib/rspec/mocks/any_instance.rb

@@ -0,0 +1,7 @@
+require 'rspec/mocks/any_instance/chain'
+require 'rspec/mocks/any_instance/stub_chain'
+require 'rspec/mocks/any_instance/stub_chain_chain'
+require 'rspec/mocks/any_instance/expect_chain_chain'
+require 'rspec/mocks/any_instance/expectation_chain'
+require 'rspec/mocks/any_instance/message_chains'
+require 'rspec/mocks/any_instance/recorder'

lib/rspec/mocks/matchers/expectation_customization.rb

@@ -0,0 +1,20 @@
+module RSpec
+  module Mocks
+    module Matchers
+      # @private
+      class ExpectationCustomization
+        attr_accessor :block
+
+        def initialize(method_name, args, block)
+          @method_name = method_name
+          @args        = args
+          @block       = block
+        end
+
+        def playback_onto(expectation)
+          expectation.__send__(@method_name, *@args, &@block)
+        end
+      end
+    end
+  end
+end

lib/rspec/mocks/matchers/receive.rb

@@ -1,3 +1,5 @@
+require 'rspec/mocks/matchers/expectation_customization'
+
 module RSpec
   module Mocks
     module Matchers
@@ -101,20 +103,5 @@ def move_block_to_last_customization(block)
         end
       end
     end
-
-    # @private
-    class ExpectationCustomization
-      attr_accessor :block
-
-      def initialize(method_name, args, block)
-        @method_name = method_name
-        @args        = args
-        @block       = block
-      end
-
-      def playback_onto(expectation)
-        expectation.__send__(@method_name, *@args, &@block)
-      end
-    end
   end
 end

lib/rspec/mocks/matchers/receive_message_chain.rb

@@ -1,3 +1,5 @@
+require 'rspec/mocks/matchers/expectation_customization'
+
 module RSpec
   module Mocks
     module Matchers

lib/rspec/mocks/targets.rb

@@ -37,16 +37,9 @@ def self.disallow_negation(method_name)
     private
 
       def matcher_allowed?(matcher)
-        ALLOWED_MATCHERS.include?(matcher.class)
+        matcher.class.name.start_with?("RSpec::Mocks::Matchers".freeze)
       end
 
-      #@api private
-      ALLOWED_MATCHERS = [
-        Matchers::Receive,
-        Matchers::ReceiveMessages,
-        Matchers::ReceiveMessageChain,
-      ]
-
       def define_matcher(matcher, name, &block)
         matcher.__send__(name, @target, &block)
       end