Merge pull request #2553 from jasujm/jasujm/input_adapter_custom_cont…

…ainer Fix compilation of input_adapter(container) in edge cases
nlohmann · Dec 29, 2020 · ff3863d · ff3863d
2 parents dfedefb + 467f622
commit ff3863d
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Showing 3 changed files with 80 additions and 13 deletions.
diff --git a/include/nlohmann/detail/input/input_adapters.hpp b/include/nlohmann/detail/input/input_adapters.hpp
@@ -371,14 +371,35 @@ typename iterator_input_adapter_factory<IteratorType>::adapter_type input_adapte
 }
 
 // Convenience shorthand from container to iterator
+// Enables ADL on begin(container) and end(container)
+// Encloses the using declarations in namespace for not to leak them to outside scope
+
+namespace container_input_adapter_factory_impl {
+
+using std::begin;
+using std::end;
+
+template<typename ContainerType, typename Enable = void>
+struct container_input_adapter_factory {};
+
 template<typename ContainerType>
-auto input_adapter(const ContainerType& container) -> decltype(input_adapter(begin(container), end(container)))
+struct container_input_adapter_factory< ContainerType,
+                                        void_t<decltype(begin(std::declval<ContainerType>()), end(std::declval<ContainerType>()))> >
 {
-    // Enable ADL
-    using std::begin;
-    using std::end;
+    using adapter_type = decltype(input_adapter(begin(std::declval<ContainerType>()), end(std::declval<ContainerType>())));
+
+    static adapter_type create(const ContainerType& container)
+    {
+        return input_adapter(begin(container), end(container));
+    }
+};
+
+}
 
-    return input_adapter(begin(container), end(container));
+template<typename ContainerType>
+typename container_input_adapter_factory_impl::container_input_adapter_factory<ContainerType>::adapter_type input_adapter(const ContainerType& container)
+{
+    return container_input_adapter_factory_impl::container_input_adapter_factory<ContainerType>::create(container);
 }
 
 // Special cases with fast paths

diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
@@ -5183,14 +5183,35 @@ typename iterator_input_adapter_factory<IteratorType>::adapter_type input_adapte
 }
 
 // Convenience shorthand from container to iterator
+// Enables ADL on begin(container) and end(container)
+// Encloses the using declarations in namespace for not to leak them to outside scope
+
+namespace container_input_adapter_factory_impl {
+
+using std::begin;
+using std::end;
+
+template<typename ContainerType, typename Enable = void>
+struct container_input_adapter_factory {};
+
 template<typename ContainerType>
-auto input_adapter(const ContainerType& container) -> decltype(input_adapter(begin(container), end(container)))
+struct container_input_adapter_factory< ContainerType,
+                                        void_t<decltype(begin(std::declval<ContainerType>()), end(std::declval<ContainerType>()))> >
 {
-    // Enable ADL
-    using std::begin;
-    using std::end;
+    using adapter_type = decltype(input_adapter(begin(std::declval<ContainerType>()), end(std::declval<ContainerType>())));
+
+    static adapter_type create(const ContainerType& container)
+    {
+        return input_adapter(begin(container), end(container));
+    }
+};
 
-    return input_adapter(begin(container), end(container));
+}
+
+template<typename ContainerType>
+typename container_input_adapter_factory_impl::container_input_adapter_factory<ContainerType>::adapter_type input_adapter(const ContainerType& container)
+{
+    return container_input_adapter_factory_impl::container_input_adapter_factory<ContainerType>::create(container);
 }
 
 // Special cases with fast paths
@@ -16801,7 +16822,7 @@ class basic_json
         detail::parser_callback_t<basic_json>cb = nullptr,
         const bool allow_exceptions = true,
         const bool ignore_comments = false
-                                 )
+    )
     {
         return ::nlohmann::detail::parser<basic_json, InputAdapterType>(std::move(adapter),
                 std::move(cb), allow_exceptions, ignore_comments);
@@ -25346,7 +25367,7 @@ template<>
 inline void swap<nlohmann::json>(nlohmann::json& j1, nlohmann::json& j2) noexcept(
     is_nothrow_move_constructible<nlohmann::json>::value&&
     is_nothrow_move_assignable<nlohmann::json>::value
-                              )
+)
 {
     j1.swap(j2);
 }

diff --git a/test/src/unit-user_defined_input.cpp b/test/src/unit-user_defined_input.cpp
@@ -63,7 +63,7 @@ const char* end(const MyContainer& c)
     return c.data + strlen(c.data);
 }
 
-TEST_CASE("Custom container")
+TEST_CASE("Custom container non-member begin/end")
 {
 
     MyContainer data{"[1,2,3,4]"};
@@ -75,6 +75,31 @@ TEST_CASE("Custom container")
 
 }
 
+TEST_CASE("Custom container member begin/end")
+{
+    struct MyContainer2
+    {
+        const char* data;
+
+        const char* begin() const
+        {
+            return data;
+        }
+
+        const char* end() const
+        {
+            return data + strlen(data);
+        }
+    };
+
+    MyContainer2 data{"[1,2,3,4]"};
+    json as_json = json::parse(data);
+    CHECK(as_json.at(0) == 1);
+    CHECK(as_json.at(1) == 2);
+    CHECK(as_json.at(2) == 3);
+    CHECK(as_json.at(3) == 4);
+}
+
 TEST_CASE("Custom iterator")
 {
     const char* raw_data = "[1,2,3,4]";