json_pointer not functioning as expected from docs

[clarkholdham]

json::json_pointer access not working as expected from here with root "/". I've tried with the string literal as well as standard json::json_pointer constructors as well.

Code:

#include <nlohmann/json.hpp>

#include <iostream>

int main() {
    nlohmann::json data = {{"data", {}}};
    nlohmann::json::json_pointer p = "/"_json_pointer;
    std::cout << "No pointer: " << data.dump() << std::endl;
    try {
        std::cout << "Checked access pointer: " << data.at(p).dump()
                  << std::endl;
    } catch (std::exception& e) {
        std::cout << "Json error: " << e.what() << std::endl;
    }
    try {
        std::cout << "Unchecked access pointer: " << data[p].dump()
                  << std::endl;
    } catch (std::exception& e) {
        std::cout << "Json error: " << e.what() << std::endl;
    }
}

Actual:

No pointer: {"data":null}
Checked access pointer: Json error: [json.exception.out_of_range.403] key '' not found
Unchecked access pointer: null

Expected:

No pointer: {"data":null}
Checked access pointer: {"data":null}
Unchecked access pointer: {"data":null}

[falbrechtskirchinger]

The JSON pointer "/" refers to the object member with the key "". From the RFC:

For example, given the JSON document

   {
      "foo": ["bar", "baz"],
      "": 0,
      "a/b": 1,
      "c%d": 2,
      "e^f": 3,
      "g|h": 4,
      "i\\j": 5,
      "k\"l": 6,
      " ": 7,
      "m~n": 8
   }

The following JSON strings evaluate to the accompanying values:

    ""           // the whole document
    "/foo"       ["bar", "baz"]
    "/foo/0"     "bar"
    "/"          0
    "/a~1b"      1
    "/c%d"       2
    "/e^f"       3
    "/g|h"       4
    "/i\\j"      5
    "/k\"l"      6
    "/ "         7
    "/m~0n"      8

Edit: The documentation you referenced is in fact wrong.