Why Mongoose doesn't validate on update?

I have this code

var ClientSchema = new Schema({
  name: {type: String, required: true, trim: true}
});

var Client = mongoose.model('Client', ClientSchema);

Using express, I create a new client with this code

var client = new Client(req.body);
client.save(function(err, data) {
  ....
});

If I leave the name field empty on the form, mongoose doesn't allow to create the client because I set it as required on the schema. Also, if I leave spaces before and after the name, mongoose delete that spaces before save.

Now, I try to update a client with this code

var id = req.params.id;
var client = req.body;
Client.update({_id: id}, client, function(err) {
  ....
});

It let me to change the name, but if I leave it empty on the form, mongoose doesn't validate and save an empty name. If I add empty spaces before and after the name, it save the name with spaces.

Why mongoose validate on save but not on update? I'm doing it in the wrong way?

mongodb: 2.4.0 mongoose: 3.6.0 express: 3.1.0 node: 0.10.1

As of Mongoose 4.0 you can run validators on update() and findOneAndUpdate() using the new flag runValidators: true.

> Mongoose 4.0 introduces an option to run validators on update() and > findOneAndUpdate() calls. Turning this option on will run validators > for all fields that your update() call tries to $set or $unset.

For example, given OP's Schema:

const ClientSchema = new Schema({
  name: {type: String, required: true, trim: true}
});

const Client = mongoose.model('Client', ClientSchema);

Passing the flag on each update

You can use the new flag like this:

const id = req.params.id;
const client = req.body;
Client.update({_id: id}, client, { runValidators: true }, function(err) {
  ....
});

Using the flag on a pre hook

If you don't want to set the flag every time you update something, you can set a pre hook for findOneAndUpdate():

// Pre hook for `findOneAndUpdate`
ClientSchema.pre('findOneAndUpdate', function(next) {
  this.options.runValidators = true;
  next();
});

Then you can update() using the validators without passing the runValidators flag every time.

You're not doing anything wrong, validation is implemented as internal middleware within Mongoose and middleware doesn't get executed during an update as that's basically a pass-through to the native driver.

If you want your client update validated you'll need to find the object to update, apply the new property values to it (see underscore's extend method), and then call save on it.

Mongoose 4.0 Update

As noted in the comments and victorkohl's answer, Mongoose now support the validation of the fields of $set and $unset operators when you include the runValidators: true option in the update call.

MongoDB does not run validation on updates by default.

in order to make validation works by default when an update happens, just before connecting to MongoDB you can set global setting only ones like that:

mongoose.set('runValidators', true); // here is your global setting

mongoose.connect(config.database, { useNewUrlParser: true });
mongoose.connection.once('open', () => {
    console.log('Connection has been made, start making fireworks...');
}).on('error', function (error) {
	console.log('Connection error:', error);
});

So any built-in or custom validation will run on any update as well

You can run validation while update by setting the option runValidators: true.

Example 1:

const Kitten = db.model('Kitten', kittenSchema);

const update = { color: 'blue' };
const opts = { runValidators: true };
Kitten.updateOne({}, update, opts, function() {
  // code
});

Example 2:

const Kitten = db.model('Kitten', kittenSchema);

const update = { color: 'blue' };
const opts = { runValidators: true };
Kitten.updateOne(
  {
    _id: req.params.id
  },
  {
    $set: { ...update },
  },
  opts
).then(result => {
    // code
})

Read More: https://mongoosejs.com/docs/validation.html#update-validators

The accepted answer does not work if you use upsert in the findOneAndUpdate options. The way around this is to create a model static method that does a findOne and then updateOne or create under the hood. create runs validation automatically.

export async function findOneAndUpdateWithValidation(
  this: LocationModel,
  filter: FilterQuery<LocationDocument>,
  update: UpdateQuery<LocationDocument>,
  options?: QueryOptions
) {
  const documentFound = await this.findOne(filter);
  
  if (!documentFound) return this.create(update);

  return this.updateOne(filter, update, options);
}

locationSchema.statics = {
  findOneAndUpdateWithValidation
}

If you add this option in your config of mongoose it works:

mongoose.set('runValidators', true)

In your model, ex. Category.js file:

const CategorySchema = mongoose.Schema({
category_name : {
type : String,
required : [true, 'Category Name Is Required !'],
trim : true,
maxlength : [30, 'Category Name Is To Long !'],
unique : true,
});
const Category = module.exports = mongoose.model("Category",CategorySchema);

In your route file:

router.put("/",(req,res,next)=>{
  Category.findOneAndUpdate(
  {_id : req.body.categoryId},
  {$set : {category_name : req.body.category_name} },
  **{runValidators: true}**, function(err,result) {
    if(err){
      if(err.code === 11000){
       var duplicateValue = err.message.match(/".*"/);
       res.status(200).json({"defaultError":duplicateValue[0]+" Is Already Exsist !"});
       }else{
         res.status(200).json({"error":err.message} || {"defaultError":'Error But Not Understood !'});
       }
    }else{
     console.log("From category.js (Route File) = "+result);
     res.status(200).json({"success":"Category Updated Successfully!!"});
    }
});