Custom type with Combine(). Fix for #3781

3 files changed, 112 insertions, 1 deletions

diff --git a/googletest/include/gtest/gtest-param-test.h b/googletest/include/gtest/gtest-param-test.h
index b55119a..d59e552 100644
--- a/googletest/include/gtest/gtest-param-test.h
+++ b/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 {                                               \
diff --git a/googletest/include/gtest/gtest.h b/googletest/include/gtest/gtest.h
index d19a587..0c97f6c 100644
--- a/googletest/include/gtest/gtest.h
+++ b/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:
diff --git a/googletest/include/gtest/internal/gtest-param-util.h b/googletest/include/gtest/internal/gtest-param-util.h
index e7af2f9..c643a3b 100644
--- a/googletest/include/gtest/internal/gtest-param-util.h
+++ b/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