I've started migrating my project to Mobx v4 (v4.2.0) and have run into some issues along the way. The main issue I've found in rfx-core is that the @toggle decorator no longer works.

In v4, the @observable decorator moves the prop from the class to the instance. Since @toggle decorates the class, an issue arises that throws an error preventing further page loading.

Error: [mobx] Property 'isOpen' of '[object Object]' was accessed through the prototype chain. Use 'decorate' instead to declare the prop or access it statically through it's owner

From the mobx gitter channel:

Michel Weststrate @mweststrate 12:15
@pdfowler yeah decorators don't compose atm, as @observable etc will redefine the property and move it from the class to the instance. Which unfortunately cannot be expressed neatly in the current decorators implementations (the current stage 2 proposal fixes that)

TODO:

• Re-Implement @toggle to be compatible with mobx-4
• Confirm that @extend works as intended