From 5eddcc134df81791b455e7eb0e3d4ef3a623ce0e Mon Sep 17 00:00:00 2001
From: Alexander Karzhenkov <karzhenkov@mail.ru>
Date: Fri, 21 Aug 2020 10:05:51 +0500
Subject: [PATCH] Allow to use string_view from std::experimental

---
 include/nlohmann/detail/macro_scope.hpp | 19 ++++++++++++
 include/nlohmann/json.hpp               |  2 +-
 single_include/nlohmann/json.hpp        | 21 ++++++++++++-
 test/src/unit-conversions.cpp           | 39 ++++++++++++-------------
 4 files changed, 58 insertions(+), 23 deletions(-)

diff --git a/include/nlohmann/detail/macro_scope.hpp b/include/nlohmann/detail/macro_scope.hpp
index 77acf04c7..8dd34ac97 100644
--- a/include/nlohmann/detail/macro_scope.hpp
+++ b/include/nlohmann/detail/macro_scope.hpp
@@ -31,6 +31,25 @@
     #define JSON_HAS_CPP_14
 #endif
 
+namespace nlohmann {
+namespace std_aliases { }
+using namespace std_aliases;
+}
+
+#if defined(JSON_HAS_CPP_17)
+    #if __has_include(<string_view>)
+        #include <string_view>
+        namespace nlohmann::std_aliases {
+            using std::string_view;
+        }
+    #elif __has_include(<experimental/string_view>)
+        #include <experimental/string_view>
+        namespace nlohmann::std_aliases {
+            using std::experimental::string_view;
+        }
+    #endif
+#endif
+
 // disable float-equal warnings on GCC/clang
 #if defined(__clang__) || defined(__GNUC__) || defined(__GNUG__)
     #pragma GCC diagnostic push
diff --git a/include/nlohmann/json.hpp b/include/nlohmann/json.hpp
index cd56dafdc..e9bb1afd4 100644
--- a/include/nlohmann/json.hpp
+++ b/include/nlohmann/json.hpp
@@ -3230,7 +3230,7 @@ class basic_json
                    !detail::is_basic_json<ValueType>::value
                    && !std::is_same<ValueType, std::initializer_list<typename string_t::value_type>>::value
 #if defined(JSON_HAS_CPP_17) && (defined(__GNUC__) || (defined(_MSC_VER) && _MSC_VER >= 1910 && _MSC_VER <= 1914))
-                   && !std::is_same<ValueType, typename std::string_view>::value
+                   && !std::is_same<ValueType, string_view>::value
 #endif
                    && detail::is_detected<detail::get_template_function, const basic_json_t&, ValueType>::value
                    , int >::type = 0 >
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index e9dbc87da..2ba6c4051 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -2048,6 +2048,25 @@ JSON_HEDLEY_DIAGNOSTIC_POP
     #define JSON_HAS_CPP_14
 #endif
 
+namespace nlohmann {
+namespace std_aliases { }
+using namespace std_aliases;
+}
+
+#if defined(JSON_HAS_CPP_17)
+    #if __has_include(<string_view>)
+        #include <string_view>
+        namespace nlohmann::std_aliases {
+            using std::string_view;
+        }
+    #elif __has_include(<experimental/string_view>)
+        #include <experimental/string_view>
+        namespace nlohmann::std_aliases {
+            using std::experimental::string_view;
+        }
+    #endif
+#endif
+
 // disable float-equal warnings on GCC/clang
 #if defined(__clang__) || defined(__GNUC__) || defined(__GNUG__)
     #pragma GCC diagnostic push
@@ -19736,7 +19755,7 @@ class basic_json
                    !detail::is_basic_json<ValueType>::value
                    && !std::is_same<ValueType, std::initializer_list<typename string_t::value_type>>::value
 #if defined(JSON_HAS_CPP_17) && (defined(__GNUC__) || (defined(_MSC_VER) && _MSC_VER >= 1910 && _MSC_VER <= 1914))
-                   && !std::is_same<ValueType, typename std::string_view>::value
+                   && !std::is_same<ValueType, string_view>::value
 #endif
                    && detail::is_detected<detail::get_template_function, const basic_json_t&, ValueType>::value
                    , int >::type = 0 >
diff --git a/test/src/unit-conversions.cpp b/test/src/unit-conversions.cpp
index c71e230d9..091c4130c 100644
--- a/test/src/unit-conversions.cpp
+++ b/test/src/unit-conversions.cpp
@@ -32,6 +32,7 @@ SOFTWARE.
 #define JSON_TESTS_PRIVATE
 #include <nlohmann/json.hpp>
 using nlohmann::json;
+using namespace nlohmann::std_aliases;
 
 #include <deque>
 #include <forward_list>
@@ -48,10 +49,6 @@ using nlohmann::json;
     #define JSON_HAS_CPP_14
 #endif
 
-#if defined(JSON_HAS_CPP_17)
-    #include <string_view>
-#endif
-
 TEST_CASE("value conversion")
 {
     SECTION("get an object (explicit)")
@@ -465,7 +462,7 @@ TEST_CASE("value conversion")
 #if defined(JSON_HAS_CPP_17)
         SECTION("std::string_view")
         {
-            std::string_view s = j.get<std::string_view>();
+            string_view s = j.get<string_view>();
             CHECK(json(s) == j);
         }
 #endif
@@ -514,27 +511,27 @@ TEST_CASE("value conversion")
 #if defined(JSON_HAS_CPP_17)
         SECTION("exception in case of a non-string type using string_view")
         {
-            CHECK_THROWS_AS(json(json::value_t::null).get<std::string_view>(), json::type_error&);
-            CHECK_THROWS_AS(json(json::value_t::object).get<std::string_view>(), json::type_error&);
-            CHECK_THROWS_AS(json(json::value_t::array).get<std::string_view>(), json::type_error&);
-            CHECK_THROWS_AS(json(json::value_t::boolean).get<std::string_view>(), json::type_error&);
-            CHECK_THROWS_AS(json(json::value_t::number_integer).get<std::string_view>(), json::type_error&);
-            CHECK_THROWS_AS(json(json::value_t::number_unsigned).get<std::string_view>(), json::type_error&);
-            CHECK_THROWS_AS(json(json::value_t::number_float).get<std::string_view>(), json::type_error&);
+            CHECK_THROWS_AS(json(json::value_t::null).get<string_view>(), json::type_error&);
+            CHECK_THROWS_AS(json(json::value_t::object).get<string_view>(), json::type_error&);
+            CHECK_THROWS_AS(json(json::value_t::array).get<string_view>(), json::type_error&);
+            CHECK_THROWS_AS(json(json::value_t::boolean).get<string_view>(), json::type_error&);
+            CHECK_THROWS_AS(json(json::value_t::number_integer).get<string_view>(), json::type_error&);
+            CHECK_THROWS_AS(json(json::value_t::number_unsigned).get<string_view>(), json::type_error&);
+            CHECK_THROWS_AS(json(json::value_t::number_float).get<string_view>(), json::type_error&);
 
-            CHECK_THROWS_WITH(json(json::value_t::null).get<std::string_view>(),
+            CHECK_THROWS_WITH(json(json::value_t::null).get<string_view>(),
                               "[json.exception.type_error.302] type must be string, but is null");
-            CHECK_THROWS_WITH(json(json::value_t::object).get<std::string_view>(),
+            CHECK_THROWS_WITH(json(json::value_t::object).get<string_view>(),
                               "[json.exception.type_error.302] type must be string, but is object");
-            CHECK_THROWS_WITH(json(json::value_t::array).get<std::string_view>(),
+            CHECK_THROWS_WITH(json(json::value_t::array).get<string_view>(),
                               "[json.exception.type_error.302] type must be string, but is array");
-            CHECK_THROWS_WITH(json(json::value_t::boolean).get<std::string_view>(),
+            CHECK_THROWS_WITH(json(json::value_t::boolean).get<string_view>(),
                               "[json.exception.type_error.302] type must be string, but is boolean");
-            CHECK_THROWS_WITH(json(json::value_t::number_integer).get<std::string_view>(),
+            CHECK_THROWS_WITH(json(json::value_t::number_integer).get<string_view>(),
                               "[json.exception.type_error.302] type must be string, but is number");
-            CHECK_THROWS_WITH(json(json::value_t::number_unsigned).get<std::string_view>(),
+            CHECK_THROWS_WITH(json(json::value_t::number_unsigned).get<string_view>(),
                               "[json.exception.type_error.302] type must be string, but is number");
-            CHECK_THROWS_WITH(json(json::value_t::number_float).get<std::string_view>(),
+            CHECK_THROWS_WITH(json(json::value_t::number_float).get<string_view>(),
                               "[json.exception.type_error.302] type must be string, but is number");
         }
 #endif
@@ -562,7 +559,7 @@ TEST_CASE("value conversion")
         SECTION("std::string_view")
         {
             std::string s = "previous value";
-            std::string_view sv = s;
+            string_view sv = s;
             j.get_to(sv);
             CHECK(json(sv) == j);
         }
@@ -617,7 +614,7 @@ TEST_CASE("value conversion")
 #if defined(JSON_HAS_CPP_17)
         SECTION("std::string_view")
         {
-            std::string_view s = j.get<std::string_view>();
+            string_view s = j.get<string_view>();
             CHECK(json(s) == j);
         }
 #endif