mongoose-unique-validator

mongoose-unique-validator
=========================

mongoose-unique-validator is a plugin which adds pre-save validation for unique fields within a Mongoose schema.

This makes error handling much easier, since you will get a Mongoose validation error when you attempt to violate a
unique constraint, rather than an E11000 error
from MongoDB.

Usage
-----

Yarn: yarn add mongoose-unique-validator

NPM: npm install --save mongoose-unique-validator

Then, apply the plugin to your schema:

``js
const mongoose = require('mongoose');
const uniqueValidator = require('mongoose-unique-validator');

const mySchema = mongoose.Schema(/ put your schema definition here /);
mySchema.plugin(uniqueValidator);
`

Example
-------

Let’s say you have a user schema. You can easily add validation for the unique constraints in this schema by applying
the uniqueValidator plugin to your user schema:

`js
const mongoose = require('mongoose');
const uniqueValidator = require('mongoose-unique-validator');

// Define your schema as normal.
const userSchema = mongoose.Schema({
username: { type: String, required: true, unique: true },
email: { type: String, index: true, unique: true, required: true },
password: { type: String, required: true }
});

// Apply the uniqueValidator plugin to userSchema.
userSchema.plugin(uniqueValidator);
`

Now when you try to save a user, the unique validator will check for duplicate database entries and report them just
like any other validation error:

`js
const user = new User({ username: 'JohnSmith', email: 'john.smith@gmail.com', password: 'j0hnNYb0i' });
user.save(function (err) {
console.log(err);
});
`

`js
{
message: 'Validation failed',
name: 'ValidationError',
errors: {
username: {
message: 'Error, expected username to be unique. Value: JohnSmith',
name: 'ValidatorError',
kind: 'unique',
path: 'username',
value: 'JohnSmith'
}
}
}
`

Find + Updates
--------------

When using findOneAndUpdate and related methods, mongoose doesn't automatically run validation. To trigger this,
you need to pass a configuration object. For technical reasons, this plugin requires that you also set the context
option to query.

{ runValidators: true, context: 'query' }

A full example:

`js
User.findOneAndUpdate(
{ email: 'old-email@example.com' },
{ email: 'new-email@example.com' },
{ runValidators: true, context: 'query' },
function(err) {
// ...
}
)
`

Custom Error Types
------------------

You can pass through a custom error type as part of the optional options argument:

`js
userSchema.plugin(uniqueValidator, { type: 'mongoose-unique-validator' });
`

After running the above example the output will be:

`js
{
message: 'Validation failed',
name: 'ValidationError',
errors: {
username: {
message: 'Error, expected username to be unique. Value: JohnSmith',
name: 'ValidatorError',
kind: 'mongoose-unique-validator',
path: 'username',
value: 'JohnSmith'
}
}
}
`

You can also specify a default custom error type by overriding the plugin defaults.type variable:

`js
uniqueValidator.defaults.type = 'mongoose-unique-validator'
`

Custom Error Messages
---------------------

You can pass through a custom error message as part of the optional options argument:

`js
userSchema.plugin(uniqueValidator, { message: 'Error, expected {PATH} to be unique.' });
`

You have access to all of the standard Mongoose error message templating:

* {PATH}
* {VALUE}
* {TYPE}

You can also specify a default custom error message by overriding the plugin defaults.message variable:

`js
uniqueValidator.defaults.message = 'Error, expected {PATH} to be unique.'
`


Case Insensitive
---------------------

For case-insensitive matches, include the uniqueCaseInsensitive option in your schema. Queries will treat john.smith@gmail.com and John.Smith@gmail.com as duplicates.

`js
const userSchema = mongoose.Schema({
username: { type: String, required: true, unique: true },
email: { type: String, index: true, unique: true, required: true, uniqueCaseInsensitive: true },
password: { type: String, required: true }
});
`

Additional Conditions
---------------------

For additional unique-constraint conditions (ex: only enforce unique constraint on non soft-deleted records), the MongoDB option partialFilterExpression can be used.

Note: the option index must be passed as an object containing unique: true, or else partialFilterExpression will be ignored.

`js
const userSchema = mongoose.Schema({
username: { type: String, required: true, unique: true },
email: {
type: String,
required: true,
index: {
unique: true,
partialFilterExpression: { deleted: false }
}
},
password: { type: String, required: true }
});
``

Caveats
-------

Because we rely on async operations to verify whether a document exists in the database, it's possible for two queries to execute at the same time, both get 0 back, and then both insert into MongoDB.

Outside of automatically locking the collection or forcing a single connection, there's no real solution.

For most of our users this won't be a problem, but is an edge case to be aware of.