Cannot read property 'toString' of null

[pjpronk]

Description

I am using a mongoDB database and mongoose to save a session. I pass the serialised data into my saveSession function and upload it to my database.

When I load the session by using ig.state.deserialize() no error is thrown, but an error is throws when I try to use any other function of the igApiCleint.

In my database the cookies variable was saved as a string. I thought the problem lied here, so I thought I could solve the problem by saving it as a JSON object.
When I add the line
serialized.cookies = JSON.parse(serialized.cookies);
then the cookies are saved as a JSON object.

I thought this would fix the error, but unfortunately it did not. So now I don't really know where the error could lie.

Error

TypeError: Cannot read property 'toString' of null
    at Request.getDefaultHeaders (/VSCodeProjects/Swapper/node_modules/instagram-private-api/src/core/request.ts:188:103)
    at Request.send (/VSCodeProjects/Swapper/node_modules/instagram-private-api/src/core/request.ts:68:23)
    at UserRepository.search (/VSCodeProjects/Swapper/node_modules/instagram-private-api/src/repositories/user.repository.ts:32:48)
    at UserRepository.searchExact (/VSCodeProjects/Swapper/node_modules/instagram-private-api/src/repositories/user.repository.ts:45:31)
    at UserRepository.getIdByUsername (/VSCodeProjects/Swapper/node_modules/instagram-private-api/src/repositories/user.repository.ts:95:29)
    at Object.it (/VSCodeProjects/Swapper/tests/instafunctions.test.js:13:44)

Code

export{};
import {IgApiClient} from "instagram-private-api";
const Session = require('../models/models').Session;

/**
 * Loads the session to the database.
 *
 * @param par_username {string} - Username of the user to save session for.
 * @return {Promise<void>} - Empty promise.
 */
async function loadSession(par_username) : Promise<any>
{
   return Session.findOne({username: par_username}).then((result) => {
       return result;
   }).catch((error) => {
       return error;
   });
}

/**
 * Saves the session to the database.
 *
 * @param par_username {string} - Username of the user to save session for.
 * @param serialized {JSON} - Serialized session data.
 * @return {Promise<void>} - Empty promise.
 */
function saveSession(par_username : string, serialized : JSON) : void
{
    const query = {'username': par_username};
    const options = {
        upsert: true,
        useFindAndModify : false,
        new: true,
        setDefaultsOnInsert: true
    };
    const change = {$set:{'session' : serialized}};

    return Session.findOneAndUpdate(query, change, options, function(err, doc) {
        if (err) throw new Error(err);
    });
}


/**
 * Gets IgApiClient from username and password.
 * If a certain username has a session, then this session is used to create the IgApiClient
 *
 * @param username {string} - Username of the user to get IgApiClient for.
 * @param password {string} - Password of the user to get IgApiClient for.
 * @return {Promise<IgApiClient>} - Promise of an IgApiClient
 */
async function getIgApiClient(username : string, password : string) : Promise<IgApiClient> {

    //Create a new client to return back to the user.
    const ig = new IgApiClient();
    await ig.state.generateDevice(username);

    //The code that has to be executed after every request.
    //Saves the state and cookies to database.
    ig.request.end$.subscribe(async () => {
        const serialized = await ig.state.serialize();
//Line I thought would fix the problem
        //serialized.cookies = JSON.parse(serialized.cookies);
        delete serialized.constants;
        saveSession((await ig.account.currentUser()).username, serialized);
    });

    const existingSession = await loadSession(username);
    if(existingSession != null){
        //The code to load a user from the session database if it exists
        await ig.state.deserialize(existingSession.session).catch((error) => {
            throw new Error(error);
        });
        return ig;
    }
    else {
        //The code to create a user through login
        console.log("Creating session for: " + username);
        await ig.account.login(username, password).catch((error) => {
            throw new Error(error);
        });
        await ig.simulate.postLoginFlow();
        return ig;
    }

}
exports.getIgApiClient = getIgApiClient;

[Nerixyz]

The serialized output has euDCEnabled set to null, it should be undefined | boolean. Your state sets undefined to null. When saving the state (saveSession), you can use JSON.stringify(serialize) to "clear" any undefined values.

[pjpronk]

Thanks @Nerixyz for the fast reply!
Your solution worked perfectly by adding the line:
serialized = JSON.parse(JSON.stringify(serialized));