4.0 Release Notes

Mongoose 4.0 brings some exciting new functionality: schema validation in the browser, query middleware, validation on update, and promises for async operations. In addition to these improvements, there are a few backwards breaking changes to be aware of when you choose to upgrade. The 3.8 branch will continue to be maintained until August 1, 2015.

First, a note on versioning. As of 4.0, Mongoose will return to using semantic versioning rather than the even/odd versioning system that NodeJS and MongoDB use. The even/odd versioning caused a lot of confusion and made releases much larger than they had to be. Each Mongoose release after 4.0 will be considered production-ready, and there will be no more backwards-breaking changes until 5.0.

Backwards-Breaking Changes

• #1349: setProfiling() was removed.
• #1351: Document no longer inherits from EventEmitter. Documents still fulfill the NodeJS EventEmitter API through function wrappers, but Document instanceof EventEmitter is no longer true. This is to prevent users from accidentally clobbering EventEmitter internals by creating schema paths named "domain", "_events", etc.
• #2306: If options.cursor is specified, aggregate.exec() will return a cursor and ignore any callback.
• #2380: "save" and "validate" may no longer be schema path names.
• #2552: Upgraded mongodb driver to 2.0.x. Mongoose is a wrapper layer on top of the MongoDB node driver. The mongodb driver recently released version 2.0, which includes numerous performance and usability improvements. The new driver, however, introduces a few changes that affect the way you use Mongoose:
  • If you are connecting to a replica set, you must specify the replicaSet option in the connection string.