Handle discriminators with insertMany()

[vkarpov15]

Re: #6087 (comment), there may be an issue with BaseModel.insertMany() not respecting discriminator keys.

[Fonger]

I can't reproduce this on 5.5.9.
The following code works for me. I also tried with __t without { discriminatorKey: 'kind' },
pre('validation') and Number type with min, max, required validator.

repro script (can't reproduce)

  /**
   * When you use `Model.create()`, mongoose will pull the correct type from
   * the discriminator key for you.
   */
  it('Using discriminators with `Model.create()` or `Model.insertMany()`', function(done) {
    var Schema = mongoose.Schema;
    var shapeSchema = new Schema({
      name: String
    }, { discriminatorKey: 'kind' });
    var squareSchema = new Schema({ side: Number });
    var validateCount = 0;
    squareSchema.pre('validate', function() {
      validateCount++;
    });

    var Shape = db.model('Shape', shapeSchema);

    var Circle = Shape.discriminator('Circle',
      new Schema({ radius: Number }));
    var Square = Shape.discriminator('Square', squareSchema);

    var shapeObjects = [
      { name: 'Test' },
      { kind: 'Circle', radius: 5 },
      { kind: 'Square', side: 10 }
    ];

    Shape.create(shapeObjects).then(function(shapes) { // test model.create
      assert.ok(shapes[0] instanceof Shape);
      assert.ok(shapes[1] instanceof Circle);
      assert.equal(shapes[1].radius, 5);
      assert.ok(shapes[2] instanceof Square);
      assert.equal(shapes[2].side, 10);
      return Shape.insertMany(shapeObjects); // test model.insertMany
    }).then(function(shapes) {
      assert.ok(shapes[0] instanceof Shape);
      assert.ok(shapes[1] instanceof Circle);
      assert.equal(shapes[1].radius, 5);
      assert.ok(shapes[2] instanceof Square);
      assert.equal(shapes[2].side, 10);
      assert.equal(validateCount, 2);
      done();
    }).
    catch(done);
  });

Data in DB

$ npm test -- -g "Using discriminators with"

> mongoose@5.5.9 test /home/fonger/mongoose
> mocha --exit test/*.test.js test/**/*.test.js "-g" "Using discriminators with"


 You're not testing shards! 
 Please set the MONGOOSE_SHARD_TEST_URI env variable. 
 e.g: `mongodb://localhost:27017/database 
 Sharding must already be enabled on your database


  ․

  1 passing (130ms)


$ mongo
> use mongoose_test
switched to db mongoose_test
> db.shapes.find({}).pretty()
{ "_id" : ObjectId("5ce000d3a6a1014a1cc9fc46"), "name" : "Test", "__v" : 0 }
{
	"_id" : ObjectId("5ce000d3a6a1014a1cc9fc47"),
	"__t" : "Circle",
	"radius" : 5,
	"__v" : 0
}
{
	"_id" : ObjectId("5ce000d3a6a1014a1cc9fc48"),
	"__t" : "Square",
	"side" : 10,
	"__v" : 0
}
{ "_id" : ObjectId("5ce000d3a6a1014a1cc9fc49"), "name" : "Test", "__v" : 0 }
{
	"_id" : ObjectId("5ce000d3a6a1014a1cc9fc4a"),
	"__t" : "Circle",
	"radius" : 5,
	"__v" : 0
}
{
	"_id" : ObjectId("5ce000d3a6a1014a1cc9fc4b"),
	"__t" : "Square",
	"side" : 10,
	"__v" : 0
}

Unlike Model.create() which new Model based on its discriminator keys, Model.insertMany() directly call new _this(doc). I thought it was the source of bug. However it seems this is handled during the initialization of document internally and I was unable to reproduce this bug with the script above.

Model.create() new model based on discriminator key

mongoose/lib/model.js

Lines 2874 to 2882 in 5011b56

	args.forEach(doc => {
	toExecute.push(callback => {
	const Model = this.discriminators && doc[discriminatorKey] != null ?
	this.discriminators[doc[discriminatorKey]] || getDiscriminatorByValue(this, doc[discriminatorKey]) :
	this;
	if (Model == null) {
	throw new Error(`Discriminator "${doc[discriminatorKey]}" not ` +
	`found for model "${this.modelName}"`);
	}

mongoose/lib/model.js

Lines 2894 to 2897 in 5011b56

	if (!(toSave instanceof Model)) {
	try {
	toSave = new Model(toSave);
	} catch (error) {

Model.insertMany() new model based on this

mongoose/lib/model.js

Lines 3061 to 3065 in 5011b56

	arr.forEach(function(doc) {
	toExecute.push(function(callback) {
	if (!(doc instanceof _this)) {
	doc = new _this(doc);
	}

[ValYouW]

Yes, it seems that there was a change between version 5.3.15 and 5.5.9 that fixed how docs are saved...
I had the following issue on 5.3.15:

var ShapeSchema = new db.Schema({
	type: {type: String},
	name: String,
}, {collection: 'shapes', discriminatorKey: 'type'});

var ShapeModel = db.model('ShapeModel', ShapeSchema);

var SquareSchema = new db.Schema({
	radius: Number
});

var CircleModel = ShapeModel.discriminator('Circle', SquareSchema);


var dalDoc = new ShapeModel({type: 'Circle', radius: 12});
dalDoc.save().then(res => {
	console.log('Inserted --->> ', res.toJSON());
});

//// Output on 5.3.15
Inserted --->>  { _id: 5ce10ca93ca3ff1964d15ce1, type: 'Circle', __v: 0 }

//// Output on 5.5.9
Inserted --->>  { _id: 5ce10cdc6d05443ba4107f43,
  type: 'Circle',
  radius: 12,
  __v: 0 
}

So looks good :)

[vkarpov15]

@ValYouW @Fonger confirmed this was fixed in 5.4.20, looks like this fix was a positive but unexpected side effect of #7586