onremove fails with nested component children when the view return false

[octavore]

When a component receives class components as children but returns nothing in its view, onremove will try to call onremove on the children but fails because the children were never initialized. This does not happen if the component returns a vnode because in this case there is a check for vnode.instance that avoids the loop.

Expected Behavior

When navigating, onremove should not try to invoke the onremove handler of undefined _state.

Current Behavior

Appears to silently fail to change the dom.

Possible Solution

Maybe add a check that vnode._state is defined here?

Steps to Reproduce

// component which fails to be removed
class GrandchildComponent {
  view() {
    return m('div', 'hello')
  }
}

// if this component returns a vnode, the bug does not happen
class ChildComponent {
  view(v) {
    return;
  }
}

// setup for testing: click the link to trigger navigation, which fails due to the bug
class ParentComponent {
  view() {
    return [
      m('div', m('a', { href: '/b', oncreate: m.route.link }, 'next')),
      m(ChildComponent, {}, m('div', m(GrandchildComponent)))
    ]
  }
}

var root = document.getElementById("app");
m.route(root, '/', {
  '/': ParentComponent,
  '/b': { view: () => m('div', 'world')}
})

Context

The situation where I encountered this bug was with a Popover component where the parent could specify the visibility (as a boolean attribute) and children of the Popover, and if the visibility was false the view would simply return nothing. However, child components which were classes would subsequently fail onremove when navigating to a different URL.

Your Environment

• Version used: 1.1.3 and 1da69da
• Browser Name and version: Safari 10.1.1, Chrome 60
• Operating System and version (desktop or mobile): MacOS 10.12.5
• Link to your project: https://github.com/ketchuphq/ketchup

[pygy]

@octavore thanks for the report, you're right, we should not iterate over the children of components, not matter what the view returns

[pygy]

It was merged into next ideally it should also be cherry picked for a v1.1.x release