gmock-actions: add support for move-only values to Return.
`Return(x)` can now be used directly with `WillOnce` (the only place it makes
sense in the type system), without using `ByMove`.
PiperOrigin-RevId: 448380066
Change-Id: Ia71cc60ccbc3b99720662731a2d309735a5ce7c8
diff --git a/googlemock/include/gmock/gmock-actions.h b/googlemock/include/gmock/gmock-actions.h
index df2effd..e5981f9 100644
--- a/googlemock/include/gmock/gmock-actions.h
+++ b/googlemock/include/gmock/gmock-actions.h
@@ -881,6 +881,17 @@
template <typename U, typename... Args,
typename = typename std::enable_if<conjunction<
// See the requirements documented on Return.
+ negation<std::is_same<void, U>>, //
+ negation<std::is_reference<U>>, //
+ std::is_convertible<R, U>, //
+ std::is_move_constructible<U>>::value>::type>
+ operator OnceAction<U(Args...)>() && { // NOLINT
+ return Impl<U>(std::move(value_));
+ }
+
+ template <typename U, typename... Args,
+ typename = typename std::enable_if<conjunction<
+ // See the requirements documented on Return.
negation<std::is_same<void, U>>, //
negation<std::is_reference<U>>, //
std::is_convertible<const R&, U>, //
@@ -894,9 +905,17 @@
template <typename U>
class Impl final {
public:
+ // The constructor used when the return value is allowed to move from the
+ // input value (i.e. we are converting to OnceAction).
+ explicit Impl(R&& input_value)
+ : state_(new State(std::move(input_value))) {}
+
+ // The constructor used when the return value is not allowed to move from
+ // the input value (i.e. we are converting to Action).
explicit Impl(const R& input_value) : state_(new State(input_value)) {}
- U operator()() const { return state_->value; }
+ U operator()() && { return std::move(state_->value); }
+ U operator()() const& { return state_->value; }
private:
// We put our state on the heap so that the compiler-generated copy/move
@@ -923,6 +942,18 @@
// explicit constructor from R.
value(ImplicitCast_<U>(internal::as_const(input_value))) {}
+ // As above, but for the case where we're moving from the ReturnAction
+ // object because it's being used as a OnceAction.
+ explicit State(R&& input_value_in)
+ : input_value(std::move(input_value_in)),
+ // For the same reason as above we make an implicit conversion to U
+ // before initializing the value.
+ //
+ // Unlike above we provide the input value as an rvalue to the
+ // implicit conversion because this is a OnceAction: it's fine if it
+ // wants to consume the input value.
+ value(ImplicitCast_<U>(std::move(input_value))) {}
+
// A copy of the value originally provided by the user. We retain this in
// addition to the value of the mock function's result type below in case
// the latter is a reference-like type. See the std::string_view example
@@ -1740,18 +1771,19 @@
// Creates an action that returns a value.
//
-// R must be copy-constructible. The returned type can be used as an
-// Action<U(Args...)> for any type U where all of the following are true:
+// The returned type can be used with a mock function returning a non-void,
+// non-reference type U as follows:
//
-// * U is not void.
-// * U is not a reference type. (Use ReturnRef instead.)
-// * U is copy-constructible.
-// * const R& is convertible to U.
+// * If R is convertible to U and U is move-constructible, then the action can
+// be used with WillOnce.
//
-// The Action<U(Args)...> object contains the R value from which the U return
-// value is constructed (a copy of the argument to Return). This means that the
-// R value will survive at least until the mock object's expectations are
-// cleared or the mock object is destroyed, meaning that U can be a
+// * If const R& is convertible to U and U is copy-constructible, then the
+// action can be used with both WillOnce and WillRepeatedly.
+//
+// The mock expectation contains the R value from which the U return value is
+// constructed (a move/copy of the argument to Return). This means that the R
+// value will survive at least until the mock object's expectations are cleared
+// or the mock object is destroyed, meaning that U can safely be a
// reference-like type such as std::string_view:
//
// // The mock function returns a view of a copy of the string fed to
@@ -1794,6 +1826,8 @@
return internal::ReturnRefOfCopyAction<R>(x);
}
+// DEPRECATED: use Return(x) directly with WillOnce.
+//
// Modifies the parent action (a Return() action) to perform a move of the
// argument instead of a copy.
// Return(ByMove()) actions can only be executed once and will assert this
diff --git a/googlemock/test/gmock-actions_test.cc b/googlemock/test/gmock-actions_test.cc
index 414c615..9aa9f81 100644
--- a/googlemock/test/gmock-actions_test.cc
+++ b/googlemock/test/gmock-actions_test.cc
@@ -47,6 +47,7 @@
#include "gmock/gmock-actions.h"
#include <algorithm>
+#include <functional>
#include <iterator>
#include <memory>
#include <string>
@@ -709,6 +710,24 @@
EXPECT_THAT(mock.AsStdFunction()(), Field(&Out::x, 19));
}
+// It should be possible to use Return(R) with a mock function result type U
+// that is convertible from const R& but *not* R (such as
+// std::reference_wrapper). This should work for both WillOnce and
+// WillRepeatedly.
+TEST(ReturnTest, ConversionRequiresConstLvalueReference) {
+ using R = int;
+ using U = std::reference_wrapper<const int>;
+
+ static_assert(std::is_convertible<const R&, U>::value, "");
+ static_assert(!std::is_convertible<R, U>::value, "");
+
+ MockFunction<U()> mock;
+ EXPECT_CALL(mock, Call).WillOnce(Return(17)).WillRepeatedly(Return(19));
+
+ EXPECT_EQ(17, mock.AsStdFunction()());
+ EXPECT_EQ(19, mock.AsStdFunction()());
+}
+
// Return(x) should not be usable with a mock function result type that's
// implicitly convertible from decltype(x) but requires a non-const lvalue
// reference to the input. It doesn't make sense for the conversion operator to
@@ -731,32 +750,33 @@
// It shouldn't be possible to use the result of Return(std::string) in a
// context where an S is needed.
+ //
+ // Here too we disable the assertion for MSVC, since its incorrect
+ // implementation of is_convertible causes our SFINAE to be wrong.
using RA = decltype(Return(std::string()));
static_assert(!std::is_convertible<RA, Action<S()>>::value, "");
+#ifndef _MSC_VER
static_assert(!std::is_convertible<RA, OnceAction<S()>>::value, "");
+#endif
}
-// Return(x) should not be usable with a mock function result type that's
-// implicitly convertible from decltype(x) but requires an rvalue reference to
-// the input. We don't yet support handing over the value for consumption.
-TEST(ReturnTest, ConversionRequiresRvalueReference) {
- // Set up a type that is implicitly convertible from std::string&& and
- // `const std::string&&`, but not `const std::string&`.
- struct S {
- S(std::string&&) {} // NOLINT
- S(const std::string&&) {} // NOLINT
- };
+TEST(ReturnTest, MoveOnlyResultType) {
+ // Return should support move-only result types when used with WillOnce.
+ {
+ MockFunction<std::unique_ptr<int>()> mock;
+ EXPECT_CALL(mock, Call)
+ // NOLINTNEXTLINE
+ .WillOnce(Return(std::unique_ptr<int>(new int(17))));
- static_assert(std::is_convertible<std::string, S>::value, "");
- static_assert(!std::is_convertible<const std::string&, S>::value, "");
+ EXPECT_THAT(mock.AsStdFunction()(), Pointee(17));
+ }
- // It shouldn't be possible to use the result of Return(std::string) in a
- // context where an S is needed.
- using RA = decltype(Return(std::string()));
-
- static_assert(!std::is_convertible<RA, Action<S()>>::value, "");
- static_assert(!std::is_convertible<RA, OnceAction<S()>>::value, "");
+ // The result of Return should not be convertible to Action (so it can't be
+ // used with WillRepeatedly).
+ static_assert(!std::is_convertible<decltype(Return(std::unique_ptr<int>())),
+ Action<std::unique_ptr<int>()>>::value,
+ "");
}
// Tests that Return(v) is covaraint.
