Custom type with Combine(). Fix for #3781

docs/reference/testing.md

@@ -109,6 +109,7 @@ namespace:
 | `ValuesIn(container)` or `ValuesIn(begin,end)` | Yields values from a C-style array, an STL-style container, or an iterator range `[begin, end)`. |
 | `Bool()`                     | Yields sequence `{false, true}`.            |
 | `Combine(g1, g2, ..., gN)`   | Yields as `std::tuple` *n*-tuples all combinations (Cartesian product) of the values generated by the given *n* generators `g1`, `g2`, ..., `gN`. |
+| `ConvertGenerator<T>(g)`     | Yields values generated by generator `g`, `static_cast` to `T`. |
 
 The optional last argument *`name_generator`* is a function or functor that
 generates custom test name suffixes based on the test parameters. The function

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

@@ -407,6 +407,46 @@ internal::CartesianProductHolder<Generator...> Combine(const Generator&... g) {
   return internal::CartesianProductHolder<Generator...>(g...);
 }
 
+// ConvertGenerator() wraps a parameter generator in order to cast each prduced
+// value through a known type before supplying it to the test suite
+//
+// Synopsis:
+// ConvertGenerator<T>(gen)
+//   - returns a generator producing the same elements as generated by gen, but
+//     each element is static_cast to type T before being returned
+//
+// It is useful when using the Combine() function to get the generated
+// parameters in a custom type instead of std::tuple
+//
+// Example:
+//
+// This will instantiate tests in test suite AnimalTest each one with
+// the parameter values tuple("cat", BLACK), tuple("cat", WHITE),
+// tuple("dog", BLACK), and tuple("dog", WHITE):
+//
+// enum Color { BLACK, GRAY, WHITE };
+// struct ParamType {
+//   using TupleT = std::tuple<const char*, Color>;
+//   std::string animal;
+//   Color color;
+//   ParamType(TupleT t) : animal(std::get<0>(t)), color(std::get<1>(t)) {}
+// };
+// class AnimalTest
+//     : public testing::TestWithParam<ParamType> {...};
+//
+// TEST_P(AnimalTest, AnimalLooksNice) {...}
+//
+// INSTANTIATE_TEST_SUITE_P(AnimalVariations, AnimalTest,
+//                          ConvertGenerator<ParamType::TupleT>(
+//                              Combine(Values("cat", "dog"),
+//                                      Values(BLACK, WHITE))));
+//
+template <typename T>
+internal::ParamConverterGenerator<T> ConvertGenerator(
+    internal::ParamGenerator<T> gen) {
+  return internal::ParamConverterGenerator<T>(gen);
+}
+
 #define TEST_P(test_suite_name, test_name)                                     \
   class GTEST_TEST_CLASS_NAME_(test_suite_name, test_name)                     \
       : public test_suite_name {                                               \

googletest/include/gtest/gtest.h

@@ -1625,7 +1625,7 @@ class GTEST_API_ AssertHelper {
 // the GetParam() method.
 //
 // Use it with one of the parameter generator defining functions, like Range(),
-// Values(), ValuesIn(), Bool(), and Combine().
+// Values(), ValuesIn(), Bool(), Combine(), and ConvertGenerator<T>().
 //
 // class FooTest : public ::testing::TestWithParam<int> {
 //  protected:

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

@@ -950,6 +950,77 @@ class CartesianProductHolder {
   std::tuple<Gen...> generators_;
 };
 
+template <typename From, typename To>
+class ParamGeneratorConverter : public ParamGeneratorInterface<To> {
+ public:
+  ParamGeneratorConverter(ParamGenerator<From> gen)
+      : generator_(std::move(gen)) {}
+
+  ParamIteratorInterface<To>* Begin() const override {
+    return new Iterator(this, generator_.begin(), generator_.end());
+  }
+  ParamIteratorInterface<To>* End() const override {
+    return new Iterator(this, generator_.end(), generator_.end());
+  }
+
+ private:
+  class Iterator : public ParamIteratorInterface<To> {
+   public:
+    Iterator(const ParamGeneratorInterface<To>* base, ParamIterator<From> it,
+             ParamIterator<From> end)
+        : base_(base), it_(it), end_(end) {
+      if (it_ != end_) value_ = std::make_shared<To>(static_cast<To>(*it_));
+    }
+    ~Iterator() override {}
+
+    const ParamGeneratorInterface<To>* BaseGenerator() const override {
+      return base_;
+    }
+    void Advance() override {
+      ++it_;
+      if (it_ != end_) value_ = std::make_shared<To>(static_cast<To>(*it_));
+    }
+    ParamIteratorInterface<To>* Clone() const override {
+      return new Iterator(*this);
+    }
+    const To* Current() const override { return value_.get(); }
+    bool Equals(const ParamIteratorInterface<To>& other) const override {
+      // Having the same base generator guarantees that the other
+      // iterator is of the same type and we can downcast.
+      GTEST_CHECK_(BaseGenerator() == other.BaseGenerator())
+          << "The program attempted to compare iterators "
+          << "from different generators." << std::endl;
+      const ParamIterator<From> other_it =
+          CheckedDowncastToActualType<const Iterator>(&other)->it_;
+      return it_ == other_it;
+    }
+
+   private:
+    Iterator(const Iterator& other) = default;
+
+    const ParamGeneratorInterface<To>* const base_;
+    ParamIterator<From> it_;
+    ParamIterator<From> end_;
+    std::shared_ptr<To> value_;
+  };  // class ParamGeneratorConverter::Iterator
+
+  ParamGenerator<From> generator_;
+};  // class ParamGeneratorConverter
+
+template <class Gen>
+class ParamConverterGenerator {
+ public:
+  ParamConverterGenerator(ParamGenerator<Gen> g) : generator(g) {}
+
+  template <typename T>
+  operator ParamGenerator<T>() const {
+    return ParamGenerator<T>(new ParamGeneratorConverter<Gen, T>(generator));
+  }
+
+ private:
+  ParamGenerator<Gen> generator;
+};
+
 }  // namespace internal
 }  // namespace testing
 

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

@@ -51,6 +51,7 @@ using ::std::vector;
 using ::testing::AddGlobalTestEnvironment;
 using ::testing::Bool;
 using ::testing::Combine;
+using ::testing::ConvertGenerator;
 using ::testing::Message;
 using ::testing::Range;
 using ::testing::TestWithParam;
@@ -402,7 +403,7 @@ TEST(BoolTest, BoolWorks) {
 TEST(CombineTest, CombineWithTwoParameters) {
   const char* foo = "foo";
   const char* bar = "bar";
-  const ParamGenerator<std::tuple<const char*, int> > gen =
+  const ParamGenerator<std::tuple<const char*, int>> gen =
       Combine(Values(foo, bar), Values(3, 4));
 
   std::tuple<const char*, int> expected_values[] = {
@@ -413,7 +414,7 @@ TEST(CombineTest, CombineWithTwoParameters) {
 
 // Tests that Combine() with three parameters generates the expected sequence.
 TEST(CombineTest, CombineWithThreeParameters) {
-  const ParamGenerator<std::tuple<int, int, int> > gen =
+  const ParamGenerator<std::tuple<int, int, int>> gen =
       Combine(Values(0, 1), Values(3, 4), Values(5, 6));
   std::tuple<int, int, int> expected_values[] = {
       std::make_tuple(0, 3, 5), std::make_tuple(0, 3, 6),
@@ -427,7 +428,7 @@ TEST(CombineTest, CombineWithThreeParameters) {
 // sequence generates a sequence with the number of elements equal to the
 // number of elements in the sequence generated by the second parameter.
 TEST(CombineTest, CombineWithFirstParameterSingleValue) {
-  const ParamGenerator<std::tuple<int, int> > gen =
+  const ParamGenerator<std::tuple<int, int>> gen =
       Combine(Values(42), Values(0, 1));
 
   std::tuple<int, int> expected_values[] = {std::make_tuple(42, 0),
@@ -439,7 +440,7 @@ TEST(CombineTest, CombineWithFirstParameterSingleValue) {
 // sequence generates a sequence with the number of elements equal to the
 // number of elements in the sequence generated by the first parameter.
 TEST(CombineTest, CombineWithSecondParameterSingleValue) {
-  const ParamGenerator<std::tuple<int, int> > gen =
+  const ParamGenerator<std::tuple<int, int>> gen =
       Combine(Values(0, 1), Values(42));
 
   std::tuple<int, int> expected_values[] = {std::make_tuple(0, 42),
@@ -450,7 +451,7 @@ TEST(CombineTest, CombineWithSecondParameterSingleValue) {
 // Tests that when the first parameter produces an empty sequence,
 // Combine() produces an empty sequence, too.
 TEST(CombineTest, CombineWithFirstParameterEmptyRange) {
-  const ParamGenerator<std::tuple<int, int> > gen =
+  const ParamGenerator<std::tuple<int, int>> gen =
       Combine(Range(0, 0), Values(0, 1));
   VerifyGeneratorIsEmpty(gen);
 }
@@ -458,7 +459,7 @@ TEST(CombineTest, CombineWithFirstParameterEmptyRange) {
 // Tests that when the second parameter produces an empty sequence,
 // Combine() produces an empty sequence, too.
 TEST(CombineTest, CombineWithSecondParameterEmptyRange) {
-  const ParamGenerator<std::tuple<int, int> > gen =
+  const ParamGenerator<std::tuple<int, int>> gen =
       Combine(Values(0, 1), Range(1, 1));
   VerifyGeneratorIsEmpty(gen);
 }
@@ -469,7 +470,7 @@ TEST(CombineTest, CombineWithMaxNumberOfParameters) {
   const char* foo = "foo";
   const char* bar = "bar";
   const ParamGenerator<
-      std::tuple<const char*, int, int, int, int, int, int, int, int, int> >
+      std::tuple<const char*, int, int, int, int, int, int, int, int, int>>
       gen =
           Combine(Values(foo, bar), Values(1), Values(2), Values(3), Values(4),
                   Values(5), Values(6), Values(7), Values(8), Values(9));
@@ -497,11 +498,11 @@ class NonDefaultConstructAssignString {
 };
 
 TEST(CombineTest, NonDefaultConstructAssign) {
-  const ParamGenerator<std::tuple<int, NonDefaultConstructAssignString> > gen =
+  const ParamGenerator<std::tuple<int, NonDefaultConstructAssignString>> gen =
       Combine(Values(0, 1), Values(NonDefaultConstructAssignString("A"),
                                    NonDefaultConstructAssignString("B")));
 
-  ParamGenerator<std::tuple<int, NonDefaultConstructAssignString> >::iterator
+  ParamGenerator<std::tuple<int, NonDefaultConstructAssignString>>::iterator
       it = gen.begin();
 
   EXPECT_EQ(0, std::get<0>(*it));
@@ -523,6 +524,63 @@ TEST(CombineTest, NonDefaultConstructAssign) {
   EXPECT_TRUE(it == gen.end());
 }
 
+template <typename T>
+class ConstructFromT {
+ public:
+  ConstructFromT(const T& t) : t_(t) {}
+  template <typename... Args>
+  ConstructFromT(Args&&... args) : t_(std::forward<Args>(args)...) {}
+
+  bool operator==(const ConstructFromT& other) const { return other.t_ == t_; }
+
+  const T& get() const { return t_; }
+
+ private:
+  T t_;
+};
+
+TEST(ConvertTest, CombineWithTwoParameters) {
+  const char* foo = "foo";
+  const char* bar = "bar";
+  const ParamGenerator<ConstructFromT<std::tuple<const char*, int>>> gen =
+      ConvertGenerator<std::tuple<const char*, int>>(
+          Combine(Values(foo, bar), Values(3, 4)));
+
+  ConstructFromT<std::tuple<const char*, int>> expected_values[] = {
+      {foo, 3}, {foo, 4}, {bar, 3}, {bar, 4}};
+  VerifyGenerator(gen, expected_values);
+}
+
+TEST(ConvertTest, NonDefaultConstructAssign) {
+  const ParamGenerator<
+      ConstructFromT<std::tuple<int, NonDefaultConstructAssignString>>>
+      gen = ConvertGenerator<std::tuple<int, NonDefaultConstructAssignString>>(
+          Combine(Values(0, 1), Values(NonDefaultConstructAssignString("A"),
+                                       NonDefaultConstructAssignString("B"))));
+
+  ParamGenerator<ConstructFromT<
+      std::tuple<int, NonDefaultConstructAssignString>>>::iterator it =
+      gen.begin();
+
+  EXPECT_EQ(0, std::get<0>(it->get()));
+  EXPECT_EQ("A", std::get<1>(it->get()).str());
+  ++it;
+
+  EXPECT_EQ(0, std::get<0>(it->get()));
+  EXPECT_EQ("B", std::get<1>(it->get()).str());
+  ++it;
+
+  EXPECT_EQ(1, std::get<0>(it->get()));
+  EXPECT_EQ("A", std::get<1>(it->get()).str());
+  ++it;
+
+  EXPECT_EQ(1, std::get<0>(it->get()));
+  EXPECT_EQ("B", std::get<1>(it->get()).str());
+  ++it;
+
+  EXPECT_TRUE(it == gen.end());
+}
+
 // Tests that an generator produces correct sequence after being
 // assigned from another generator.
 TEST(ParamGeneratorTest, AssignmentWorks) {