Add CombineTo<R>() parameters generator

googletest/include/gtest/gtest-param-test.h

@@ -332,9 +332,10 @@ internal::ParamGenerator<typename Container::value_type> ValuesIn(
 // INSTANTIATE_TEST_SUITE_P(FloatingNumbers, BazTest, Values(1, 2, 3.5));
 //
 //
-template <typename... T>
-internal::ValueArray<T...> Values(T... v) {
-  return internal::ValueArray<T...>(std::move(v)...);
+template <typename... Ts>
+internal::ParamGenerator<std::common_type_t<Ts...>> Values(Ts... vs) {
+  return ValuesIn(
+      std::array<std::common_type_t<Ts...>, sizeof...(Ts)>{std::move(vs)...});
 }
 
 // Bool() allows generating tests with parameters in a set of (false, true).
@@ -359,6 +360,47 @@ internal::ValueArray<T...> Values(T... v) {
 //
 inline internal::ParamGenerator<bool> Bool() { return Values(false, true); }
 
+// CombineTo() allows the user to combine two or more sequences to produce
+// values of a Cartesian product of those sequences' elements converted to
+// the required type.
+//
+// Synopsis:
+// CombineTo<MyClass>(gen1, gen2, ..., genN)
+//   - returns a generator producing sequences with elements coming from
+//     the Cartesian product of elements from the sequences generated by
+//     gen1, gen2, ..., genN. The sequence elements will have a type of
+//     Myclass where elements from sequences produced by gen1, gen2, ..., genN
+//     was provided to the MyClass constructor parameters.
+//
+// Example:
+//
+// This will instantiate tests in test suite AnimalTest each one with
+// the parameter values Animal("cat", BLACK), Animal("cat", WHITE),
+// Animal("dog", BLACK), and Animal("dog", WHITE):
+// enum Color { BLACK, GRAY, WHITE };
+//
+// struct Animal {
+//   std::string name;
+//   Color color;
+// };
+//
+// class AnimalTest
+//     : public testing::TestWithParam<Animal> {...};
+//
+// TEST_P(AnimalTest, AnimalLooksNice) {...}
+//
+// INSTANTIATE_TEST_SUITE_P(AnimalVariations, AnimalTest,
+//                          CombineTo<Animal>(Values("cat", "dog"),
+//                                  Values(BLACK, WHITE)));
+//
+template <typename R, typename... T>
+internal::ParamGenerator<R> CombineTo(
+    internal::ParamGenerator<T>&&... generators) {
+  return internal::ParamGenerator<R>(
+      new internal::CartesianProductGenerator<R, T...>(
+          std::forward<decltype(generators)>(generators)...));
+}
+
 // Combine() allows the user to combine two or more sequences to produce
 // values of a Cartesian product of those sequences' elements.
 //
@@ -403,9 +445,11 @@ inline internal::ParamGenerator<bool> Bool() { return Values(false, true); }
 // INSTANTIATE_TEST_SUITE_P(TwoBoolSequence, FlagDependentTest,
 //                          Combine(Bool(), Bool()));
 //
-template <typename... Generator>
-internal::CartesianProductHolder<Generator...> Combine(const Generator&... g) {
-  return internal::CartesianProductHolder<Generator...>(g...);
+template <typename... T>
+internal::ParamGenerator<std::tuple<T...>> Combine(
+    internal::ParamGenerator<T>&&... generators) {
+  return CombineTo<std::tuple<T...>, T...>(
+      std::forward<decltype(generators)>(generators)...);
 }
 
 // ConvertGenerator() wraps a parameter generator in order to cast each produced

googletest/include/gtest/internal/gtest-param-util.h

@@ -180,6 +180,11 @@ class ParamGeneratorInterface {
   virtual ParamIteratorInterface<T>* End() const = 0;
 };
 
+template <class GeneratedT,
+          typename StdFunction =
+              std::function<const GeneratedT&(const GeneratedT&)>>
+class ParamConverterGenerator;
+
 // Wraps ParamGeneratorInterface<T> and provides general generator syntax
 // compatible with the STL Container concept.
 // This class implements copy initialization semantics and the contained
@@ -201,6 +206,11 @@ class ParamGenerator {
   iterator begin() const { return iterator(impl_->Begin()); }
   iterator end() const { return iterator(impl_->End()); }
 
+  template <typename R>
+  operator ParamGenerator<R>() {
+    return ParamConverterGenerator<T>(*this);
+  }
+
  private:
   std::shared_ptr<const ParamGeneratorInterface<T>> impl_;
 };
@@ -796,39 +806,15 @@ internal::ParamGenerator<typename Container::value_type> ValuesIn(
     const Container& container);
 
 namespace internal {
-// Used in the Values() function to provide polymorphic capabilities.
-
-GTEST_DISABLE_MSC_WARNINGS_PUSH_(4100)
 
-template <typename... Ts>
-class ValueArray {
+template <typename R, typename... T>
+class CartesianProductGenerator : public ParamGeneratorInterface<R> {
  public:
-  explicit ValueArray(Ts... v) : v_(FlatTupleConstructTag{}, std::move(v)...) {}
+  using ParamType = R;
 
-  template <typename T>
-  operator ParamGenerator<T>() const {  // NOLINT
-    return ValuesIn(MakeVector<T>(std::make_index_sequence<sizeof...(Ts)>()));
-  }
+  explicit CartesianProductGenerator(ParamGenerator<T>&&... g)
+      : generators_(std::forward<decltype(g)>(g)...) {}
 
- private:
-  template <typename T, size_t... I>
-  std::vector<T> MakeVector(std::index_sequence<I...>) const {
-    return std::vector<T>{static_cast<T>(v_.template Get<I>())...};
-  }
-
-  FlatTuple<Ts...> v_;
-};
-
-GTEST_DISABLE_MSC_WARNINGS_POP_()  // 4100
-
-template <typename... T>
-class CartesianProductGenerator
-    : public ParamGeneratorInterface<::std::tuple<T...>> {
- public:
-  typedef ::std::tuple<T...> ParamType;
-
-  CartesianProductGenerator(const std::tuple<ParamGenerator<T>...>& g)
-      : generators_(g) {}
   ~CartesianProductGenerator() override = default;
 
   ParamIteratorInterface<ParamType>* Begin() const override {
@@ -916,7 +902,8 @@ class CartesianProductGenerator
 
     void ComputeCurrentValue() {
       if (!AtEnd())
-        current_value_ = std::make_shared<ParamType>(*std::get<I>(current_)...);
+        current_value_ =
+            std::make_shared<ParamType>(ParamType{*std::get<I>(current_)...});
     }
     bool AtEnd() const {
       bool at_end = false;
@@ -938,20 +925,6 @@ class CartesianProductGenerator
   std::tuple<ParamGenerator<T>...> generators_;
 };
 
-template <class... Gen>
-class CartesianProductHolder {
- public:
-  CartesianProductHolder(const Gen&... g) : generators_(g...) {}
-  template <typename... T>
-  operator ParamGenerator<::std::tuple<T...>>() const {
-    return ParamGenerator<::std::tuple<T...>>(
-        new CartesianProductGenerator<T...>(generators_));
-  }
-
- private:
-  std::tuple<Gen...> generators_;
-};
-
 template <typename From, typename To, typename Func>
 class ParamGeneratorConverter : public ParamGeneratorInterface<To> {
  public:
@@ -1020,9 +993,7 @@ class ParamGeneratorConverter : public ParamGeneratorInterface<To> {
   Func converter_;
 };  // class ParamGeneratorConverter
 
-template <class GeneratedT,
-          typename StdFunction =
-              std::function<const GeneratedT&(const GeneratedT&)>>
+template <class GeneratedT, typename StdFunction>
 class ParamConverterGenerator {
  public:
   ParamConverterGenerator(ParamGenerator<GeneratedT> g)  // NOLINT

googletest/test/googletest-param-test-test.cc

@@ -588,6 +588,70 @@ TEST(ConvertTest, NonDefaultConstructAssign) {
   EXPECT_TRUE(it == gen.end());
 }
 
+TEST(CombineToTest, DefaultConstructible) {
+  struct DefaultConstructible {
+    int x;
+    std::string s;
+
+    bool operator==(const DefaultConstructible& other) const {
+      return x == other.x && s == other.s;
+    }
+  };
+
+  static_assert(std::is_default_constructible_v<DefaultConstructible>);
+  ParamGenerator<DefaultConstructible> gen =
+      testing::CombineTo<DefaultConstructible>(Values(0, 1), Values("A", "B"));
+
+  DefaultConstructible expected_values[] = {
+      {0, "A"}, {0, "B"}, {1, "A"}, {1, "B"}};
+  VerifyGenerator(gen, expected_values);
+}
+
+TEST(CombineToTest, NonDefaultConstructible) {
+  class NonDefaultConstructible {
+   public:
+    NonDefaultConstructible(const int xArg, std::string sArg)
+        : x(xArg), s(std::move(sArg)) {}
+
+    bool operator==(const NonDefaultConstructible& other) const {
+      return x == other.x && s == other.s;
+    }
+
+   private:
+    int x;
+    std::string s;
+  };
+
+  static_assert(not std::is_default_constructible_v<NonDefaultConstructible>);
+  ParamGenerator<NonDefaultConstructible> gen =
+      testing::CombineTo<NonDefaultConstructible>(Values(0, 1),
+                                                  Values("A", "B"));
+
+  NonDefaultConstructible expected_values[] = {
+      {0, "A"}, {0, "B"}, {1, "A"}, {1, "B"}};
+  VerifyGenerator(gen, expected_values);
+}
+
+TEST(CombineToTest, CopyConstructible) {
+  struct CopyConstructible {
+    CopyConstructible(const CopyConstructible& other) = default;
+
+    bool operator==(const CopyConstructible& other) const {
+      return x == other.x && s == other.s;
+    }
+
+    int x;
+    std::string s;
+  };
+
+  static_assert(std::is_copy_constructible_v<CopyConstructible>);
+  ParamGenerator<CopyConstructible> gen = testing::CombineTo<CopyConstructible>(
+      Values(CopyConstructible{0, "A"}, CopyConstructible{1, "B"}));
+  CopyConstructible expected_values[] = {CopyConstructible{0, "A"},
+                                         CopyConstructible{1, "B"}};
+  VerifyGenerator(gen, expected_values);
+}
+
 TEST(ConvertTest, WithConverterLambdaAndDeducedType) {
   const ParamGenerator<ConstructFromT<int8_t>> gen =
       ConvertGenerator(Values("0", std::string("1")), [](const std::string& s) {