Add TupleGenerator and tuple_as_range

Author: theo-dep

src/catch2/generators/catch_generators_tuple.hpp

@@ -0,0 +1,124 @@
+//              Copyright Catch2 Authors
+// Distributed under the Boost Software License, Version 1.0.
+//   (See accompanying file LICENSE.txt or copy at
+//        https://www.boost.org/LICENSE_1_0.txt)
+
+// SPDX-License-Identifier: BSL-1.0
+#ifndef CATCH_GENERATORS_TUPLE_HPINCLUDED
+#define CATCH_GENERATORS_TUPLE_HPINCLUDED
+
+#include <catch2/generators/catch_generators.hpp>
+
+#include <array>
+#include <tuple>
+#include <type_traits>
+
+namespace Catch {
+    namespace Generators {
+        namespace Detail {
+
+            template <typename Ret,
+                      typename Tup,
+                      typename Fun,
+                      std::size_t... Idxs>
+            struct TupleRuntimeAccessTable {
+                template <std::size_t N>
+                static constexpr Ret access_tuple( Tup& tuple, Fun& fun ) {
+                    return fun( std::get<N>( tuple ) );
+                }
+
+                using AccessorFunPtr = Ret ( * )( Tup&, Fun& );
+                static constexpr std::size_t table_size{ sizeof...( Idxs ) };
+
+                static constexpr std::array<AccessorFunPtr, table_size>
+                    lookup_table{ { access_tuple<Idxs>... } };
+            };
+
+            template <typename Tup, typename Fun, std::size_t... Idxs>
+            constexpr auto
+            call_access_function( Tup& tuple,
+                                  std::size_t index,
+                                  Fun fun,
+                                  std::index_sequence<Idxs...> ) {
+                using FirstTupleIndexType = decltype( std::get<0>( tuple ) );
+                using FunReturnType =
+                    std::invoke_result_t<Fun, FirstTupleIndexType>;
+
+                constexpr auto& table{
+                    TupleRuntimeAccessTable<FunReturnType, Tup, Fun, Idxs...>::
+                        lookup_table };
+                return table[index]( tuple, fun );
+            }
+
+            template <typename Tup, typename Fun>
+            constexpr auto
+            runtime_get( Tup& tuple, std::size_t index, Fun fun ) {
+                return call_access_function(
+                    tuple,
+                    index,
+                    CATCH_FORWARD( fun ),
+                    std::make_index_sequence<std::tuple_size_v<Tup>>{} );
+            }
+
+            template <typename Tup>
+            class TupleAccessor {
+                Tup m_tuple;
+                std::size_t m_current_index;
+
+            public:
+                template <typename... Args>
+                constexpr TupleAccessor( Args&&... args ):
+                    m_tuple{ CATCH_FORWARD( args )... }, m_current_index{ 0 } {}
+
+                constexpr TupleAccessor& operator++() {
+                    ++m_current_index;
+                    return *this;
+                }
+
+                constexpr operator bool() const {
+                    return m_current_index < std::tuple_size_v<Tup>;
+                }
+
+                template <typename Fun>
+                constexpr auto perform( Fun fun ) const {
+                    return runtime_get(
+                        m_tuple, m_current_index, CATCH_FORWARD( fun ) );
+                }
+            };
+
+        } // namespace Detail
+
+        template <typename Tup>
+        class TupleGenerator final
+            : public IGenerator<Detail::TupleAccessor<Tup>> {
+            Detail::TupleAccessor<Tup> m_iterator;
+
+        public:
+            template <typename... Args>
+            TupleGenerator( Args&&... args ):
+                m_iterator{ CATCH_FORWARD( args )... } {}
+
+            const Detail::TupleAccessor<Tup>& get() const override {
+                return m_iterator;
+            }
+
+            bool next() override { return ++m_iterator; }
+        };
+
+        template <typename Tup, typename... Args>
+        auto tuple_as_range( Args&&... args ) {
+            return GeneratorWrapper<Detail::TupleAccessor<Tup>>(
+                Catch::Detail::make_unique<TupleGenerator<Tup>>(
+                    CATCH_FORWARD( args )... ) );
+        }
+
+        template <typename... Args>
+        auto tuple_as_range( Args&&... args ) {
+            return tuple_as_range<std::tuple<Args...>>(
+                CATCH_FORWARD( args )... );
+        }
+
+    } // namespace Generators
+} // namespace Catch
+
+#endif // CATCH_GENERATORS_TUPLE_HPINCLUDED

tests/SelfTest/UsageTests/Generators.tests.cpp

@@ -7,12 +7,15 @@
 // SPDX-License-Identifier: BSL-1.0
 
 #include <catch2/catch_test_macros.hpp>
+#include <catch2/catch_tostring.hpp>
 #include <catch2/generators/catch_generator_exception.hpp>
 #include <catch2/generators/catch_generators_adapters.hpp>
 #include <catch2/generators/catch_generators_random.hpp>
 #include <catch2/generators/catch_generators_range.hpp>
+#include <catch2/generators/catch_generators_tuple.hpp>
 
 #include <cstring>
+#include <sstream>
 
 
 // Generators and sections can be nested freely
@@ -321,3 +324,36 @@ TEST_CASE( "GENERATE can combine literals and generators", "[generators]" ) {
                                      random( -100, 100 ) ) ) );
     REQUIRE( i % 2 == 0 );
 }
+
+TEST_CASE( "Tuple", "[generators]" ) {
+    // imagine two different serialization to test
+    // once a serialization is tested, the second must be identical
+    static const auto std_serialization{ []( const auto& element ) {
+        std::stringstream ss;
+        ss << element;
+        return ss.str();
+    } };
+    static const auto catch2_serialization{ []( const auto& element ) {
+        return Catch::StringMaker<decltype( element )>::convert( element );
+    } };
+
+    int counter{ 0 };
+
+    const auto accessor = GENERATE( tuple_as_range( 42, "foo", 3.14 ) );
+    accessor.perform( [&]( const auto& element ) {
+        REQUIRE( std_serialization( element ) ==
+                 catch2_serialization( element ) );
+        ++counter;
+    } );
+
+    // also work with std::pair or a tuple-like
+    const auto accessor_pair =
+        GENERATE( tuple_as_range<std::pair<int, std::string>>( 42, "foo" ) );
+    accessor_pair.perform( [&]( const auto& element ) {
+        REQUIRE( std_serialization( element ) ==
+                 catch2_serialization( element ) );
+        ++counter;
+    } );
+    
+    REQUIRE( counter == 2 );
+}