Clone of unsubmitted cr/176529515. Introduce parameterless expectations.

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

@@ -1282,6 +1282,13 @@ class MockSpec {
         file, line, source_text, matchers_);
   }
 
+  // This operator overload is used to swallow the superfluous parameter list
+  // introduced by the ON/EXPECT_CALL macros. See the macro comments for more
+  // explanation.
+  MockSpec<F>& operator()(const internal::WithoutMatchers&, void* const) {
+    return *this;
+  }
+
  private:
   template <typename Function>
   friend class internal::FunctionMocker;
@@ -1836,17 +1843,76 @@ inline Expectation::Expectation(internal::ExpectationBase& exp)  // NOLINT
 
 }  // namespace testing
 
-// A separate macro is required to avoid compile errors when the name
-// of the method used in call is a result of macro expansion.
-// See CompilesWithMethodNameExpandedFromMacro tests in
-// internal/gmock-spec-builders_test.cc for more details.
-#define GMOCK_ON_CALL_IMPL_(obj, call) \
-    ((obj).gmock_##call).InternalDefaultActionSetAt(__FILE__, __LINE__, \
-                                                    #obj, #call)
-#define ON_CALL(obj, call) GMOCK_ON_CALL_IMPL_(obj, call)
+// Implementation for ON_CALL and EXPECT_CALL macros. A separate macro is
+// required to avoid compile errors when the name of the method used in call is
+// a result of macro expansion. See CompilesWithMethodNameExpandedFromMacro
+// tests in internal/gmock-spec-builders_test.cc for more details.
+//
+// This macro supports statements both with and without parameter matchers. If
+// the parameter list is omitted, gMock will accept any parameters, which allows
+// tests to be written that don't need to encode the number of method
+// parameter. This technique may only be used for non-overloaded methods.
+//
+//   // These are the same:
+//   ON_CALL(mock, NoArgsMethod()).WillByDefault(…);
+//   ON_CALL(mock, NoArgsMethod).WillByDefault(…);
+//
+//   // As are these:
+//   ON_CALL(mock, TwoArgsMethod(_, _)).WillByDefault(…);
+//   ON_CALL(mock, TwoArgsMethod).WillByDefault(…);
+//
+//   // Can also specify args if you want, of course:
+//   ON_CALL(mock, TwoArgsMethod(_, 45)).WillByDefault(…);
+//
+//   // Overloads work as long as you specify parameters:
+//   ON_CALL(mock, OverloadedMethod(_)).WillByDefault(…);
+//   ON_CALL(mock, OverloadedMethod(_, _)).WillByDefault(…);
+//
+//   // Oops! Which overload did you want?
+//   ON_CALL(mock, OverloadedMethod).WillByDefault(…);
+//     => ERROR: call to member function 'gmock_OverloadedMethod' is ambiguous
+//
+// How this works: The mock class uses two overloads of the gmock_Method
+// expectation setter method plus an operator() overload on the MockSpec object.
+// In the matcher list form, the macro expands to:
+//
+//   // This statement:
+//   ON_CALL(mock, TwoArgsMethod(_, 45))…
+//
+//   // …expands to:
+//   mock.gmock_TwoArgsMethod(_, 45)(WithoutMatchers(), nullptr)…
+//   |-------------v---------------||------------v-------------|
+//       invokes first overload        swallowed by operator()
+//
+//   // …which is essentially:
+//   mock.gmock_TwoArgsMethod(_, 45)…
+//
+// Whereas the form without a matcher list:
+//
+//   // This statement:
+//   ON_CALL(mock, TwoArgsMethod)…
+//
+//   // …expands to:
+//   mock.gmock_TwoArgsMethod(WithoutMatchers(), nullptr)…
+//   |-----------------------v--------------------------|
+//                 invokes second overload
+//
+//   // …which is essentially:
+//   mock.gmock_TwoArgsMethod(_, _)…
+//
+// The WithoutMatchers() argument is used to disambiguate overloads and to
+// block the caller from accidentally invoking the second overload directly. The
+// second argument is an internal type derived from the method signature. The
+// failure to disambiguate two overloads of this method in the ON_CALL statement
+// is how we block callers from setting expectations on overloaded methods.
+#define GMOCK_ON_CALL_IMPL_(mock_expr, Setter, call)                          \
+  ((mock_expr).gmock_##call)(::testing::internal::GetWithoutMatchers(), NULL) \
+      .Setter(__FILE__, __LINE__, #mock_expr, #call)
 
-#define GMOCK_EXPECT_CALL_IMPL_(obj, call) \
-    ((obj).gmock_##call).InternalExpectedAt(__FILE__, __LINE__, #obj, #call)
-#define EXPECT_CALL(obj, call) GMOCK_EXPECT_CALL_IMPL_(obj, call)
+#define ON_CALL(obj, call) \
+  GMOCK_ON_CALL_IMPL_(obj, InternalDefaultActionSetAt, call)
+
+#define EXPECT_CALL(obj, call) \
+  GMOCK_ON_CALL_IMPL_(obj, InternalExpectedAt, call)
 
 #endif  // GMOCK_INCLUDE_GMOCK_GMOCK_SPEC_BUILDERS_H_