Mongoose pre save middleware of subdocument not called on second save operation

Question

I have a mongoose schema with a subdocument. Both the parent schema and the child schema have pre save hooks. For example:

var mongoose = require('mongoose');
var Schema = mongoose.Schema;

var SubSchema = new Schema( { x : Number } );
SubSchema.pre('save', function (next) {
  console.log("pre save Sub");
  next();
});

var MainSchema = new Schema( { x : Number, children : [SubSchema] } );
MainSchema.pre('save', function (next) {
  console.log("pre save Main");
  next();
});
var Main = mongoose.model('Main', MainSchema);

var m = new Main();
m.children.push( { x : 42 } );

m.save( function(err, doc) {
  console.log(doc +"\n\n");
  doc.children[0].x = 43;

  doc.save( function(err, doc2) {
    console.log(doc2 + "\n\n");
  });
});

When I run this code, I get the following output:

pre save Sub
pre save Main
{ __v: 0,
  _id: 50660b319aec895a50000002,
  children: [ { x: 42, _id: 50660b319aec895a50000003 } ] }


pre save Main
{ __v: 0,
  _id: 50660b319aec895a50000002,
  children: [ { x: 43, _id: 50660b319aec895a50000003 } ] }

Any reason why the pre save hook is not running for the subdocument on the second save operation?

Answer 1

This is fixed in v3.2.0, by letting you do this:

doc.children.set(0, {x: 43})
doc.save()