mobx-state-tree: Error: [mobx-state-tree] setParent is not supposed to be called on scalar nodes

[EDITED] Change “self.items.unshift(id)” by “self.items = [id, …self.items.slice()]” fixed issue [/EDITED]

I have:

• I think something is not working as it should.
  • I’ve checked documentation and searched for existing issues

Error below only happen with mobx-state-tree 3.0. I basically put a model into a array [ self.items.unshift(model) ] This model has another model that call getParent.

works perfectly with mobx 2.2

Error: [mobx-state-tree] setParent is not supposed to be called on scalar nodes
    at fail (mobx-state-tree.module.js:2286)
    at ScalarNode$$1.setParent (mobx-state-tree.module.js:885)
    at ArrayType$$1.willChange (mobx-state-tree.module.js:2979)
    at interceptChange$$1 (mobx.module.js:2688)
    at ObservableArrayAdministration.spliceWithArray (mobx.module.js:2856)
    at Proxy.unshift (mobx.module.js:3012)
    at unshift (page.js:126)
    at executeAction$$1 (mobx.module.js:613)
    at res (mobx.module.js:605)
    at runMiddleWares (mobx-state-tree.module.js:1907)

code example. I have many pages, that only keep ids, and I have a central repository to find itens with that id. I think that issue is with “get list()”

t.model('activityPage', {
  items: t.optional(t.array(t.number), [])
})

.views(self => {
  get list() { return self.items.map(id => getRoot(self).getItem('activity', id)) }
})

.actions(self => {
  unshift(id) {
    self.items.unshift(id)
  }
})