Added support for non zero-terminated strings (fixes #704)

test/JsonArray/CMakeLists.txt

@@ -12,6 +12,7 @@ add_executable(JsonArrayTests
 	remove.cpp
 	set.cpp
 	size.cpp
+	std_string.cpp
 	subscript.cpp
 )
 

test/JsonArray/std_string.cpp

@@ -0,0 +1,39 @@
+// ArduinoJson - arduinojson.org
+// Copyright Benoit Blanchon 2014-2018
+// MIT License
+
+#include <ArduinoJson.h>
+#include <catch.hpp>
+
+static void eraseString(std::string &str) {
+  char *p = const_cast<char *>(str.c_str());
+  while (*p) *p++ = '*';
+}
+
+TEST_CASE("std::string") {
+  DynamicJsonDocument doc;
+  JsonArray &array = doc.to<JsonArray>();
+
+  SECTION("add()") {
+    std::string value("hello");
+    array.add(value);
+    eraseString(value);
+    REQUIRE(std::string("hello") == array[0]);
+  }
+
+  SECTION("set()") {
+    std::string value("world");
+    array.add("hello");
+    array.set(0, value);
+    eraseString(value);
+    REQUIRE(std::string("world") == array[0]);
+  }
+
+  SECTION("operator[]") {
+    std::string value("world");
+    array.add("hello");
+    array[0] = value;
+    eraseString(value);
+    REQUIRE(std::string("world") == array[0]);
+  }
+}