sax_parse(iterator, json_sax_t *) string callback clobbers spaces

[brhamon]

Description

Implementing a sax_parse consumer. The string callback is called with a value that has all spaces removed.

Reproduction steps

Create a SAX consumer class derived from json_sax_t. Set a breakpoint in the string method so you can examine the output of the string_t variable the parser passes in. Parse a JSON file that contains a string with at least one interior space.

The value passed to the string method has the spaces removed.

Expected vs. actual results

Input JSON:

[ "The sax parser will delete all spaces between words." ]

Expected output:

The sax parser will delete all spaces between words.

Actual output:

Thesaxparserwilldeleteallspacesbetweenwords.

Minimal code example

#include <sstream>
#include <iostream>
#include <nlohmann/json.hpp>

using json = nlohmann::json;

class string_consumer : public json::json_sax_t
{
public:
    bool string(string_t& val) override
    {
        std::cout << val << std::endl;
        return true;
    }

    bool null() override { return true; }
    bool boolean(bool val) override { return true; }
    bool number_integer(number_integer_t val) override { return true; }
    bool number_unsigned(number_unsigned_t val) override { return true; }
    bool number_float(number_float_t val, const string_t& s) override { return true; }
    bool start_object(std::size_t elements) override { return true; }
    bool end_object() override { return true; }
    bool start_array(std::size_t elements) override { return true; }
    bool end_array() override { return true; }
    bool key(string_t& val) override { return true; }
    bool binary(json::binary_t& val) override { return true; }
    bool parse_error(std::size_t position, const std::string& last_token, const json::exception& ex) override {
        return false;
    }
};

int main(int , char* []) {
    std::stringstream jf("[ \"The sax parser will delete all spaces between words.\" ]");

    string_consumer sc;

    bool result = json::sax_parse(std::istream_iterator<char>(jf), std::istream_iterator<char>(), &sc);
    return result ? 0 : 1;
}

Error messages

No error messages.

Compiler and operating system

Microsoft Visual Studio Community 2019 (Version 16.11.16), Windows SDK 10.0.18362.0

Library version

3.10.5#3 from vcpkg (version 2022-06-17-9268e366206712e38102b28dbd1617697a99ff2e)

Validation

• The bug also occurs if the latest version from the develop branch is used.
• I can successfully compile and run the unit tests.

[nlohmann]

This is not an issue of the library, but standard behavior for streams. If you want to not skip whitespace do this:

std::noskipws(jf);
bool result = json::sax_parse(std::istream_iterator<char>(jf), std::istream_iterator<char>(), &sc);

or simpler:

bool result = json::sax_parse(jf, &sc);

[brhamon]

Thanks Niels. Problem solved. Sorry to waste your time.