Added support for std::string_view (closes #1578, closes #1554)

extras/tests/CMakeLists.txt

@@ -11,6 +11,7 @@ link_libraries(ArduinoJson catch)
 
 include_directories(Helpers)
 add_subdirectory(Cpp11)
+add_subdirectory(Cpp17)
 add_subdirectory(FailingBuilds)
 add_subdirectory(IntegrationTests)
 add_subdirectory(JsonArray)

extras/tests/Cpp17/CMakeLists.txt

@@ -0,0 +1,29 @@
+# ArduinoJson - https://arduinojson.org
+# Copyright Benoit Blanchon 2014-2021
+# MIT License
+
+if(MSVC_VERSION LESS 1910)
+	return()
+endif()
+
+if(CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5)
+	return()
+endif()
+
+if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 7)
+	return()
+endif()
+
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+add_executable(Cpp17Tests
+	string_view.cpp
+)
+
+add_test(Cpp17 Cpp17Tests)
+
+set_tests_properties(Cpp17
+	PROPERTIES
+		LABELS 		"Catch"
+)

extras/tests/Cpp17/string_view.cpp

@@ -0,0 +1,79 @@
+#include <ArduinoJson.h>
+
+#include <catch.hpp>
+#include <string_view>
+
+#if !ARDUINOJSON_ENABLE_STRING_VIEW
+#  error ARDUINOJSON_ENABLE_STRING_VIEW must be set to 1
+#endif
+
+TEST_CASE("string_view") {
+  StaticJsonDocument<128> doc;
+  JsonVariant variant = doc.to<JsonVariant>();
+
+  SECTION("deserializeJson()") {
+    auto err = deserializeJson(doc, std::string_view("123", 2));
+    REQUIRE(err == DeserializationError::Ok);
+    REQUIRE(doc.as<int>() == 12);
+  }
+
+  SECTION("JsonDocument::set()") {
+    doc.set(std::string_view("123", 2));
+    REQUIRE(doc.as<std::string>() == "12");
+  }
+
+  SECTION("JsonDocument::operator[]() const") {
+    doc["ab"] = "Yes";
+    doc["abc"] = "No";
+    REQUIRE(doc[std::string_view("abc", 2)] == "Yes");
+  }
+
+  SECTION("JsonDocument::operator[]()") {
+    doc[std::string_view("abc", 2)] = "Yes";
+    REQUIRE(doc["ab"] == "Yes");
+  }
+
+  SECTION("JsonVariant::operator==()") {
+    variant.set("A");
+    REQUIRE(variant == std::string_view("AX", 1));
+    REQUIRE_FALSE(variant == std::string_view("BX", 1));
+  }
+
+  SECTION("JsonVariant::operator>()") {
+    variant.set("B");
+    REQUIRE(variant > std::string_view("AX", 1));
+    REQUIRE_FALSE(variant > std::string_view("CX", 1));
+  }
+
+  SECTION("JsonVariant::operator<()") {
+    variant.set("B");
+    REQUIRE(variant < std::string_view("CX", 1));
+    REQUIRE_FALSE(variant < std::string_view("AX", 1));
+  }
+
+  SECTION("String deduplication") {
+    doc.add(std::string_view("example one", 7));
+    REQUIRE(doc.memoryUsage() == JSON_ARRAY_SIZE(1) + 8);
+
+    doc.add(std::string_view("example two", 7));
+    REQUIRE(doc.memoryUsage() == JSON_ARRAY_SIZE(2) + 8);
+  }
+}
+
+using ARDUINOJSON_NAMESPACE::adaptString;
+
+TEST_CASE("StringViewAdapter") {
+  std::string_view str("bravoXXX", 5);
+  auto adapter = adaptString(str);
+
+  CHECK(adapter.compare(NULL) > 0);
+  CHECK(adapter.compare("alpha") > 0);
+  CHECK(adapter.compare("bravo") == 0);
+  CHECK(adapter.compare("charlie") < 0);
+
+  CHECK(adapter.equals("bravo"));
+  CHECK_FALSE(adapter.equals("charlie"));
+  CHECK_FALSE(adapter.equals(NULL));
+
+  CHECK(adapter.size() == 5);
+}