Mongoose unique validation error type - node.js

Question

I'm using this schema with mongoose 3.0.3 from npm:
var schema = new Schema({
_id: Schema.ObjectId,
email: {type: String, required: true, unique: true}
});
If I try to save a email that is already in db, I expect to get a ValidationError like if a required field is omitted. However this is not the case, I get a MongoError: E11000 duplicate key error index.
Which is not a validation error (happens even if I remove the unique:true).
Any idea why?

Answer 1

I prefer putting it in path validation mechanisms, like
UserSchema.path('email').validate(function(value, done) {
this.model('User').count({ email: value }, function(err, count) {
if (err) {
return done(err);
}
// If `count` is greater than zero, "invalidate"
done(!count);
});
}, 'Email already exists');
Then it'll just get wrapped into ValidationError and will return as first argument when you call validate or save .

Answer 2

I had some issues with the approved answer. Namely:
this.model('User') didn't work for me.
the callback done wasn't working properly.
I resolved those issues by:
UserSchema.path('email').validate(async (value) => {
const emailCount = await mongoose.models.User.countDocuments({email: value });
return !emailCount;
}, 'Email already exists');
I use async/await which is a personal preference because it is much neater: https://javascript.info/async-await.
Let me know if I got something wrong.

Answer 3

This is expected behavior
The unique: true is equivalent to setting an index in mongodb like this:
db.myCollection.ensureIndex( { "email": 1 }, { unique: true } )
To do this type of validation using Mongoose (Mongoose calls this complex validation- ie- you are not just asserting the value is a number for example), you will need to wire in to the pre-save event:
mySchema.pre("save",function(next, done) {
var self = this;
mongoose.models["User"].findOne({email : self.email},function(err, results) {
if(err) {
done(err);
} else if(results) { //there was a result found, so the email address exists
self.invalidate("email","email must be unique");
done(new Error("email must be unique"));
} else {
done();
}
});
next();
});

Answer 4

Simply response to json
try {
let end_study_year = new EndStudyYear(req.body);
await end_study_year.save();
res.json({
status: true,
message: 'បានរក្សាទុក!'
})
}catch (e) {
res.json({
status: false,
message: e.message.toString().includes('duplicate') ? 'ទិន្នន័យមានរួចហើយ' : e.message.split(':')[0] // check if duplicate message exist
})
}

Answer 5

Sorry for answering an old question. After testing I feel good to have find these answers, so I will give my experience. Both top answers are great and right, just remember that:
if your document is new, you can just validate if count is higher than 0, thats the common situation;
if your document is NOT new and has modified the unique field, you need to validate with 0 too;
if your document is NOT new and has NOT being modified, just go ahead;
Here is what I made in my code:
UserSchema.path('email').validate(async function validateDuplicatedEmail(value) {
if (!this.isNew && !this.isModified('email')) return true;
try {
const User = mongoose.model("User");
const count = await User.countDocuments({ email: value });
if (count > 0) return false;
return true;
}
catch (error) {
return false;
}
}, "Email already exists");