I have a discord bot and I've recently implemented a currency system, however, I keep getting this 'UnhandledPromiseRejectionWarning' warning in my console every time someone says a message.
I've tried using catch, but that doesn't seem to work.
Here's the full error:
(node:4633) UnhandledPromiseRejectionWarning: SequelizeUniqueConstraintError: Validation error
at Query.formatError (/Users/**censored**/node_modules/sequelize/lib/dialects/sqlite/query.js:413:16)
at Query._handleQueryResponse (/Users/**censored**/node_modules/sequelize/lib/dialects/sqlite/query.js:73:18)
at Statement.afterExecute (/Users/**censored**/node_modules/sequelize/lib/dialects/sqlite/query.js:247:31)
at Statement.replacement (/Users/**censored**/node_modules/sqlite3/lib/trace.js:19:31)
(node:4633) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 29)
JavaScript code:
client.once('ready', async() => {
const target = message.mentions.users.first() || message.author;
return message.channel.send(`${target.tag} has ${currency.getBalance(target.id)}💰`);
});
client.on('message', async message => {
if (message.author.bot) return;
currency.add(message.author.id, 1);
if (!message.content.startsWith(PREFIX)) return;
const input = message.content.slice(PREFIX.length).trim();
if (!input.length) return;
const [, command, commandArgs] = input.match(/(\w+)\s*([\s\S]*)/);
if (command === 'balance') {
const target = message.mentions.users.first() || message.author;
return message.channel.send(`${target.tag} has ${currency.getBalance(target.id)}💰`);
} else if (command === 'inventory') {
const target = message.mentions.users.first() || message.author;
const user = await Users.findByPrimary(target.id);
const items = await user.getItems();
if (!items.length) return message.channel.send(`${target.tag} has nothing!`);
return message.channel.send(`${target.tag} currently has ${items.map(i => `${i.amount} ${i.item.name}`).join(', ')}`);
} else if (command === 'transfer') {
const currentAmount = currency.getBalance(message.author.id);
const transferAmount = commandArgs.split(/ +/g).find(arg => !/<@!?\d+>/g.test(arg));
const transferTarget = message.mentions.users.first();
if (!transferAmount || isNaN(transferAmount)) return message.channel.send(`Sorry ${message.author}, that's an invalid amount.`);
if (transferAmount > currentAmount) return message.channel.send(`Sorry ${message.author}, you only have ${currentAmount}.`);
if (transferAmount <= 0) return message.channel.send(`Please enter an amount greater than zero, ${message.author}.`);
currency.add(message.author.id, -transferAmount);
currency.add(transferTarget.id, transferAmount);
return message.channel.send(`Successfully transferred ${transferAmount}💰 to ${transferTarget.tag}. Your current balance is ${currency.getBalance(message.author.id)}💰`);
} else if (command === 'buy') {
const item = await CurrencyShop.findOne({
where: {
name: {
[Op.like]: commandArgs
}
}
});
if (!item) return message.channel.send(`That item doesn't exist.`);
if (item.cost > currency.getBalance(message.author.id)) {
return message.channel.send(`You currently have ${currency.getBalance(message.author.id)}, but the ${item.name} costs ${item.cost}!`);
}
const user = await Users.findByPrimary(message.author.id);
currency.add(message.author.id, -item.cost);
await user.addItem(item);
message.channel.send(`You've bought: ${item.name}.`);
} else if (command === 'shop') {
const items = await CurrencyShop.findAll();
return message.channel.send(items.map(item => `${item.name}: ${item.cost}💰`).join('\n'), {
code: true
});
} else if (command === 'leaderboard') {
return message.channel.send(
currency.sort((a, b) => b.balance - a.balance)
.filter(user => client.users.has(user.user_id))
.first(10)
.map((user, position) => `(${position + 1}) ${(client.users.get(user.user_id).tag)}: ${user.balance}💰`)
.join('\n'), {
code: true
}
);
}
});
When using methods that return promises, you can't always assume that everything's going to work perfectly. Sometimes, something can fail, and the result will be a rejected promise. When left unhandled, an unhandledPromiseRejectionWarning is emitted, as you've encountered.
From the error, it looks like something in a sequelize query is going wrong, specifically with validation.
Always make sure you're properly handling any possibilities of rejection. Use try...catch statements or catch() methods.
Examples:
try {
const items = await CurrencyShop.findAll();
message.channel.send(...);
} catch(err) { // Even if only one promise is rejected,
console.error(err); // the code inside the 'catch' is still
} // executed.
message.channel.send('hi there')
.catch(err => console.error(err));