From befb416021b08d663b78024e6537680d93c64ac3 Mon Sep 17 00:00:00 2001
From: Thom Carter <thom@bridge-u.com>
Date: Mon, 12 Feb 2018 16:50:02 +0000
Subject: [PATCH] Define respond_to_missing? on Mocha::Mock

Fixes #321.

As of Ruby 2.4, Forwardable warns when delegating to a private method.
Warnings are shown when delegating methods to a Mocha::Mock.

To determine whether to show a warning, Forwardable tests the delegated
method with the defined? operator. Mocha uses method_missing to respond
to mocked methods. defined? uses respond_to_missing? to determine
whether or not a missing method is defined. Defining respond_to_missing?
on Mocha::Mock, in place of respond_to?, prevents warnings from being
shown.

To preserve compatibility with Ruby 1.8.7, we continue to conditionally
define respond_to?. Prior to Ruby 1.9.3, defined? returns nil for method
calls handled via method_missing, so we also only test that mocked
methods are defined? in later Ruby versions.
---
 lib/mocha/mock.rb      | 10 +++++++++-
 test/unit/mock_test.rb |  8 ++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/lib/mocha/mock.rb b/lib/mocha/mock.rb
index 69e1bcce1..c35c4256c 100644
--- a/lib/mocha/mock.rb
+++ b/lib/mocha/mock.rb
@@ -9,6 +9,7 @@
 require 'mocha/argument_iterator'
 require 'mocha/expectation_error_factory'
 require 'mocha/deprecation'
+require 'mocha/ruby_version'
 
 module Mocha
 
@@ -314,7 +315,7 @@ def method_missing(symbol, *arguments, &block)
     end
 
     # @private
-    def respond_to?(symbol, include_private = false)
+    def respond_to_missing?(symbol, include_private = false)
       if @responder then
         if @responder.method(:respond_to?).arity > 1
           @responder.respond_to?(symbol, include_private)
@@ -326,6 +327,13 @@ def respond_to?(symbol, include_private = false)
       end
     end
 
+    # @private
+    if PRE_RUBY_V19
+      def respond_to?(symbol, include_private = false)
+        respond_to_missing?(symbol, include_private)
+      end
+    end
+
     # @private
     def __verified__?(assertion_counter = nil)
       @expectations.verified?(assertion_counter)
diff --git a/test/unit/mock_test.rb b/test/unit/mock_test.rb
index 7dc02e18a..44cce4868 100644
--- a/test/unit/mock_test.rb
+++ b/test/unit/mock_test.rb
@@ -334,6 +334,14 @@ def test_should_remove_expectation_for_unstubbed_method
     assert_match(/unexpected invocation/, e.message)
   end
 
+  unless PRE_RUBY_V19
+    def test_expectation_is_defined_on_mock
+      mock = build_mock
+      mock.expects(:method1)
+      assert defined? mock.method1
+    end
+  end
+
   private
 
   def build_mock