Custom Error Messages with Mongoose

So according to the mongoose docs, you are supposed to be able to set a custom error message in the schema like so:

 var breakfastSchema = new Schema({
  eggs: {
    type: Number,
    min: [6, 'Too few eggs'],
    max: 12
  },
  bacon: {
    type: Number,
    required: [true, 'Why no bacon?']
  }
});

So I wanted to do something similar:

var emailVerificationTokenSchema = mongoose.Schema({
   email: {type: String, required: true, unique: [true, "email must be unique"]},
   token: {type: String, required: true},
   createdAt: {type: Date, required: true, default: Date.now, expires: '4h'}
});

The idea being that when you attempt to save one of these tokens, and there is already a conflicting one it’ll pump out an error message that says “email must be unique”.

However when I do something like this (where I save a token with the same email):

verificationToken.save( function (err) {
    if (err) {
      return console.log(err);
    }
    else {
      return console.log(err);
    }
});

I keep getting this:

'E11000 duplicate key error: index ___.emailVerificationToken.$email_1 dup key: { : "[email protected]

Any thoughts? Is unique parameter not supported for custom messages? Is this a viable way of going about things?

Answer

Is unique parameter not supported for custom messages?

Uniqueness in Mongoose is not a validation parameter (like required); it tells Mongoose to create a unique index in MongoDB for that field.

The uniqueness constraint is handled entirely in the MongoDB server. When you add a document with a duplicate key, the MongoDB server will return the error that you are showing (E11000...).

You have to handle these errors yourself if you want to create custom error messages. The Mongoose documentation (“Error Handling Middleware”) provides you with an example on how to create custom error handling:

emailVerificationTokenSchema.post('save', function(error, doc, next) {
  if (error.name === 'MongoError' && error.code === 11000) {
    next(new Error('email must be unique'));
  } else {
    next(error);
  }
});

(although this doesn’t provide you with the specific field for which the uniqueness constraint failed)

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