Error: Can't use $x with Number.

Any advice on trying to handle the validation on invalid query operator?

// The `amount` below is set as Number  

Transaction
  .find({ amount: { '$x': 42 } }) // note the intended invalid query operator here
  .then(() => {
    // ...
  })
  .catch((err) => {
    console.log(err); // log below
    if (err instanceof CastError) {
      // handle if cast error
    }

    return next(err);
  });

The log is:

Error: Can’t use $x with Number. at SchemaNumber.castForQuery (/…/node_modules/mongoose/lib/schema/number.js:278:13)

The err is not an instance of CastError so I don’t know how to specifically check the error above on mongoose. Currently, I set it as error 500 but I want it to change to something more specific error. Thanks!

Mongoose: v5.0.3 Nodejs: v8.9.3 Mongodb: v3.6.3

[lineus]

@vkarpov15 should we create a specific Error type to throw for this instead of the vanilla Error that’s currently thrown? This seems like an edge case, otherwise I’d have done it already.

@ctrlnot If you want to test for this specific error condition now, you could do so in a pre query hook, and return an Error you can test in your handler. Here is an example:

6927.js

#!/usr/bin/env node
'use strict';

const mongoose = require('mongoose');
mongoose.connect('mongodb://localhost:27017/test');
const conn = mongoose.connection;
const Schema = mongoose.Schema;

const schema = new Schema({
  amount: Number
});

schema.pre('findOne', function (next) {
  let validKeys = Object.keys(this.schema.path('amount').$conditionalHandlers);
  let keys = Object.keys(this.getQuery().amount);
  let badKeys = '';
  for (let key of keys) {
    if (!validKeys.includes(key)) {
      badKeys += ` ${key}`;
    }
  }
  if (badKeys.length) {
    let msg = `${badKeys}`;
    msg += badKeys.trimLeft().split(' ').length > 1
      ? ' are not valid conditions'
      : ' is not a valid condition';
    return next(new Error(msg));
  } else{
    next();
  }
});

const Test = mongoose.model('test', schema);

const test = new Test({ amount: 42 });

async function run() {
  await conn.dropDatabase();
  await test.save();
  await Test.findOne({
    amount: { $x: 5, $y: 10, $z: 15 }
  }).catch(handleConditionError);
  await Test.findOne({ amount: { $a: 42 }}).catch(handleConditionError);
  let found = await Test.findOne({ amount: { $gte: 41 } });
  console.log(found);
  return conn.close();
}

run();

function handleConditionError(e) {
  if (/not (a )?valid condition/.test(e.message)) {
    // send back http 400 Bad Request
    // return res.status(400).json({ err: e.message }) etc etc
    console.error(`400: Bad Request:${e.message}`);
  } else {
    // return res.status(500).json({ err: 'whoops' }) etc etc
    console.error('500: Something else went wrong');
  }
}

Output:

issues: ./6927.js
400: Bad Request: $x $y $z are not valid conditions
400: Bad Request: $a is not a valid condition
{ _id: 5b868927bc07590988fd2fb8, amount: 42, __v: 0 }
issues:

[lineus]

you bet 👍