Add support for std::function in MockFunction (#2277)

googlemock/include/gmock/gmock-spec-builders.h

@@ -1786,10 +1786,80 @@ void ReportUninterestingCall(CallReaction reaction, const std::string& msg);
 
 }  // namespace internal
 
-// A MockFunction<F> class has one mock method whose type is F.  It is
-// useful when you just want your test code to emit some messages and
-// have Google Mock verify the right messages are sent (and perhaps at
-// the right times).  For example, if you are exercising code:
+namespace internal {
+
+template <typename F>
+class MockFunction;
+
+template <typename R, typename... Args>
+class MockFunction<R(Args...)> {
+ public:
+  MockFunction(const MockFunction&) = delete;
+  MockFunction& operator=(const MockFunction&) = delete;
+
+  std::function<R(Args...)> AsStdFunction() {
+    return [this](Args... args) -> R {
+      return this->Call(std::forward<Args>(args)...);
+    };
+  }
+
+  // Implementation detail: the expansion of the MOCK_METHOD macro.
+  R Call(Args... args) {
+    mock_.SetOwnerAndName(this, "Call");
+    return mock_.Invoke(std::forward<Args>(args)...);
+  }
+
+  MockSpec<R(Args...)> gmock_Call(Matcher<Args>... m) {
+    mock_.RegisterOwner(this);
+    return mock_.With(std::move(m)...);
+  }
+
+  MockSpec<R(Args...)> gmock_Call(const WithoutMatchers&,
+                                  R (*)(Args...)) {
+    return this->gmock_Call(::testing::A<Args>()...);
+  }
+
+ protected:
+  MockFunction() = default;
+  ~MockFunction() = default;
+
+ private:
+  FunctionMocker<R(Args...)> mock_;
+};
+
+/*
+The SignatureOf<F> struct is a meta-function returning function signature
+corresponding to the provided F argument.
+
+It makes use of MockFunction easier by allowing it to accept more F arguments
+than just function signatures.
+
+Specializations provided here cover only a signature type itself and
+std::function. However, if need be it can be easily extended to cover also other
+types (like for example boost::function).
+*/
+
+template <typename F>
+struct SignatureOf;
+
+template <typename R, typename... Args>
+struct SignatureOf<R(Args...)> {
+  using type = R(Args...);
+};
+
+template <typename F>
+struct SignatureOf<std::function<F>> : SignatureOf<F> {};
+
+template <typename F>
+using SignatureOfT = typename SignatureOf<F>::type;
+
+}  // namespace internal
+
+// A MockFunction<F> type has one mock method whose type is
+// internal::SignatureOfT<F>.  It is useful when you just want your
+// test code to emit some messages and have Google Mock verify the
+// right messages are sent (and perhaps at the right times).  For
+// example, if you are exercising code:
 //
 //   Foo(1);
 //   Foo(2);
@@ -1823,49 +1893,33 @@ void ReportUninterestingCall(CallReaction reaction, const std::string& msg);
 // Bar("a") is called by which call to Foo().
 //
 // MockFunction<F> can also be used to exercise code that accepts
-// std::function<F> callbacks. To do so, use AsStdFunction() method
-// to create std::function proxy forwarding to original object's Call.
-// Example:
+// std::function<internal::SignatureOfT<F>> callbacks. To do so, use
+// AsStdFunction() method to create std::function proxy forwarding to
+// original object's Call. Example:
 //
 // TEST(FooTest, RunsCallbackWithBarArgument) {
 //   MockFunction<int(string)> callback;
 //   EXPECT_CALL(callback, Call("bar")).WillOnce(Return(1));
 //   Foo(callback.AsStdFunction());
 // }
+//
+// The internal::SignatureOfT<F> indirection allows to use other types
+// than just function signature type. This is typically useful when
+// providing a mock for a predefined std::function type. Example:
+//
+// using FilterPredicate = std::function<bool(string)>;
+// void MyFilterAlgorithm(FilterPredicate predicate);
+//
+// TEST(FooTest, FilterPredicateAlwaysAccepts) {
+//   MockFunction<FilterPredicate> predicateMock;
+//   EXPECT_CALL(predicateMock, Call(_)).WillRepeatedly(Return(true));
+//   MyFilterAlgorithm(predicateMock.AsStdFunction());
+// }
 template <typename F>
-class MockFunction;
-
-template <typename R, typename... Args>
-class MockFunction<R(Args...)> {
+class MockFunction : public internal::MockFunction<internal::SignatureOfT<F>> {
+  using Base = internal::MockFunction<internal::SignatureOfT<F>>;
  public:
-  MockFunction() {}
-  MockFunction(const MockFunction&) = delete;
-  MockFunction& operator=(const MockFunction&) = delete;
-
-  std::function<R(Args...)> AsStdFunction() {
-    return [this](Args... args) -> R {
-      return this->Call(std::forward<Args>(args)...);
-    };
-  }
-
-  // Implementation detail: the expansion of the MOCK_METHOD macro.
-  R Call(Args... args) {
-    mock_.SetOwnerAndName(this, "Call");
-    return mock_.Invoke(std::forward<Args>(args)...);
-  }
-
-  internal::MockSpec<R(Args...)> gmock_Call(Matcher<Args>... m) {
-    mock_.RegisterOwner(this);
-    return mock_.With(std::move(m)...);
-  }
-
-  internal::MockSpec<R(Args...)> gmock_Call(const internal::WithoutMatchers&,
-                                            R (*)(Args...)) {
-    return this->gmock_Call(::testing::A<Args>()...);
-  }
-
- private:
-  internal::FunctionMocker<R(Args...)> mock_;
+  using Base::Base;
 };
 
 // The style guide prohibits "using" statements in a namespace scope

googlemock/test/gmock-function-mocker_test.cc

@@ -40,6 +40,7 @@
 # include <objbase.h>
 #endif  // GTEST_OS_WINDOWS
 
+#include <functional>
 #include <map>
 #include <string>
 #include <type_traits>
@@ -779,6 +780,54 @@ TEST(MockMethodMockFunctionTest, AsStdFunctionWithReferenceParameter) {
 }
 
 
+namespace {
+
+template <typename Expected, typename F>
+static constexpr bool IsMockFunctionTemplateArgumentDeducedTo(const MockFunction<F>&) {
+  return std::is_same<F, Expected>::value;
+}
+
+} // namespace
+
+template <typename F>
+class MockMethodMockFunctionSignatureTest : public Test {
+};
+
+using MockMethodMockFunctionSignatureTypes = Types<
+  void(),
+  int(),
+  void(int),
+  int(int),
+  int(bool, int),
+  int(bool, char, int, int, int, int, int, char, int, bool)
+>;
+TYPED_TEST_SUITE(MockMethodMockFunctionSignatureTest, MockMethodMockFunctionSignatureTypes);
+
+TYPED_TEST(MockMethodMockFunctionSignatureTest, IsMockFunctionTemplateArgumentDeducedForRawSignature) {
+  using Argument = TypeParam;
+  MockFunction<Argument> foo;
+  EXPECT_TRUE(IsMockFunctionTemplateArgumentDeducedTo<Argument>(foo));
+}
+
+TYPED_TEST(MockMethodMockFunctionSignatureTest, IsMockFunctionTemplateArgumentDeducedForStdFunction) {
+  using Argument = std::function<TypeParam>;
+  MockFunction<Argument> foo;
+  EXPECT_TRUE(IsMockFunctionTemplateArgumentDeducedTo<Argument>(foo));
+}
+
+TYPED_TEST(MockMethodMockFunctionSignatureTest, IsMockFunctionCallMethodSignatureTheSameForRawSignatureAndStdFunction) {
+  using ForRawSignature = decltype(&MockFunction<TypeParam>::Call);
+  using ForStdFunction = decltype(&MockFunction<std::function<TypeParam>>::Call);
+  EXPECT_TRUE((std::is_same<ForRawSignature, ForStdFunction>::value));
+}
+
+TYPED_TEST(MockMethodMockFunctionSignatureTest, IsMockFunctionAsStdFunctionMethodSignatureTheSameForRawSignatureAndStdFunction) {
+  using ForRawSignature = decltype(&MockFunction<TypeParam>::AsStdFunction);
+  using ForStdFunction = decltype(&MockFunction<std::function<TypeParam>>::AsStdFunction);
+  EXPECT_TRUE((std::is_same<ForRawSignature, ForStdFunction>::value));
+}
+
+
 struct MockMethodSizes0 {
   MOCK_METHOD(void, func, ());
 };