In compatible JSON object from nlohmann::json to nohman::json - unexpected end of input; expected '[', '{', or a literal

[looopTools]

Hey I am trying to create a configuration using nlohmann::json, but for some reason I get:

terminate called after throwing an instance of 'nlohmann::detail::parse_error'
  what():  [json.exception.parse_error.101] parse error at line 1, column 1: syntax error while parsing value - unexpected end of input; expected '[', '{', or a literal
Aborted (core dumped)

I have create a JSON object with nlohmann::json like this

    nlohmann::json minerva_config;

    minerva_config["register_path"] = (USER_HOME + minervafs_root_folder + minervafs_identifier_register); // string
    minerva_config["base_register_path"] = (USER_HOME + minervafs_root_folder + minervafs_registry);       // string  
    minerva_config["base_out_path"] = (USER_HOME + minervafs_root_folder + minervafs_basis_folder);        // string
    minerva_config["out_path"] = (USER_HOME + minervafs_root_folder + "/");                                // string
    minerva_config["max_registry_size"] = 8589934592; // 8 GB of RAM

    tartarus::writers::json_writer(config_file_path, minerva_config);
    minerva_storage = minerva::minerva(minerva_config);      

The json_writer does not fail, what fails is the construct on the next line. Which gives the error presented above. I have tried to remove the writer call but no dice. The code for the constructor is like this:

   minerva::minerva(const nlohmann::json& config)
    {   
        m_base_out_path = config["base_out_path"].get<std::string>();
        m_base_registry_path = config["base_register_path"].get<std::string>();
        m_out_path = config["out_path"].get<std::string>();
        m_registry_path = config["register_path"].get<std::string>();
size_t registry_size = config["max_registry_size"].get<size_t>();
        ...
    }

Where it it interact with the nlohmann::json object. As I am within the same application I wouldn't assume system char encoding or something like that is a problem.
I tried to dump the json object and passed it in a JSON validator, the dump is as follows:

{"base_out_path":"/home/tools/.minervafs/.basis","base_register_path":"/home/tools/.minervafs/.registry","max_registry_size":8589934592,"out_path":"/home/tools/.minervafs/","register_path":"/home/tools/.minervafs/.identifiers"}

Any ideas as to what might be wrong?

[nickaein]

Is this related to #1583?

[looopTools]

@nickaein no tried that already. The problem in the issue you reference was for writing JSON and then reading it again, and the issue was due to mis-match in character encoding. Which from what I can tell is not the case this time.

[nickaein]

Is the file accessible? Try with its absolute path.

BTW, I don't get any error for this program (input.json contains the JSON dump you have provided):

#include "json.hpp"
#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    try
    {
        nlohmann::json j;
        std::ifstream fs("input.json");
        if(!fs)
        {
            std::cout << "Failed to open file" << endl;
            return 0;
        }

        fs >> j;
        std::cout << "Success." << endl;
        std::cout << "Raw content:" << endl;
        std::cout << j.dump(4) << endl;

        std::cout << "Retrieved configs:" << endl;
        std::cout << "\tbase_out_path: " << j["base_out_path"].get<std::string>() << endl;
        std::cout << "\tbase_register_path: " << j["base_register_path"].get<std::string>() << endl;
        std::cout << "\tout_path: " << j["out_path"].get<std::string>() << endl;
        std::cout << "\tregister_path: " << j["register_path"].get<std::string>() << endl;
        std::cout << "\tmax_registry_size: " << j["max_registry_size"].get<size_t>() << endl;
    }
    catch(std::exception& e)
    {
        std::cout << "Exception:" << endl;
        std::cout << e.what() << endl;
        return 0;
    }

    return 0;
}

It might help to debug the error. For me, it outputs the following as expected:

Success.
Raw content:
{
    "base_out_path": "/home/tools/.minervafs/.basis",
    "base_register_path": "/home/tools/.minervafs/.registry",
    "max_registry_size": 8589934592,
    "out_path": "/home/tools/.minervafs/",
    "register_path": "/home/tools/.minervafs/.identifiers"
}
Retrieved configs:
	base_out_path: /home/tools/.minervafs/.basis
	base_register_path: /home/tools/.minervafs/.registry
	out_path: /home/tools/.minervafs/
	register_path: /home/tools/.minervafs/.identifiers
	max_registry_size: 8589934592

[looopTools]

I triede you code above and it works.

Now I tried writing it to disk as well and reading into a new object also gives and error

and again this is not an issue with reading the file. This is an issue when parsing around the object

[looopTools]

Okay, I have actually gotten a bit further if the first string:

minerva_config["register_path"] = (USER_HOME + minervafs_root_folder + minervafs_identifier_register);

resolves to "/home/tools/.minervafs/.identifiers" then the interperter will throw the error. However if I remove either of the periods, so the string is either: "/home/tools/minervafs/.identifiers" or "/home/tools/.minervafs/identifiers" then the parses passes no problem.

What is this wizardry ???

identifiers

[nickaein]

That's weird. Can you provide a minimal working code that demonstrates this error?

Also, are you using the same file handler for writing and reading the config file? If so, you might need to rewind it (e.g. ifstream::seekg) to start reading from the beginning.

[looopTools]

@nickaein there is no file invovled this is just for the nlohmann::json object :)

[nickaein]

I see, but the exception in #1603 (comment) usually is thrown when parsing, whether it is parsing the file stream or an string. Are you still getting this exception? For instance, passing an empty string to json::parse() raises the exact same exception.

One other case that this type of exception can be thrown is during the construction of a json_pointer (e.g. this and this). While your strings have the resemblance of JSON Pointers, they are considered as JSON Pointer only if you explicitly ask for it. Also, the error code parse_error.101 in the exception doesn't seems to be related to JSON Pointers.

A minimal code to demonstrate the problem you are having would be very helpful!

[stale]

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