Polymer 3.2: TypeError cannot convert null to object

[pdesjardins90]

Description

When I try to upgrade from Polymer 3.1 to Polymer 3.2,
When creating a paper-dialog (which depends on iron-a11y-keys-behavior),
An error is thrown

Expected outcome

No error

Actual outcome

Uncaught TypeError: Cannot convert undefined or null to object (node_modules/@polymer/iron-a11y-keys-behavior/iron-a11y-keys-behavior.js:430)
at HTMLElement._attachDom (node_modules/@polymer/polymer/lib/mixins/element-mixin.js:739:24)
at HTMLElement._readyClients (node_modules/@polymer/polymer/lib/mixins/element-mixin.js:703:26)
at HTMLElement._flushClients (node_modules/@polymer/polymer/lib/mixins/property-effects.js:1734:14)
at HTMLElement._propertiesChanged (node_modules/@polymer/polymer/lib/mixins/property-effects.js:1883:12)
at HTMLElement._flushProperties (node_modules/@polymer/polymer/lib/mixins/properties-changed.js:390:14)
at HTMLElement._flushProperties (node_modules/@polymer/polymer/lib/mixins/property-effects.js:1716:13)
at HTMLElement.ready (node_modules/@polymer/polymer/lib/mixins/property-effects.js:1835:12)
at HTMLElement.ready (node_modules/@polymer/polymer/lib/mixins/element-mixin.js:687:13)
at HTMLElement.ready (node_modules/@polymer/polymer/lib/mixins/dir-mixin.js:158:13)

Steps to reproduce

Browsers Affected

• Chrome
• Firefox
• Safari 9
• Safari 8
• Safari 7
• Edge
• IE 11
• IE 10

[super-kamil]

+1

[super-kamil]

Wrap paper-dialog by an own web component and use this as a workaround:

constructor() {
    super();
    this._keyBindings = this._keyBindings || {};
}

[pdesjardins90]

I'll try that!

[balloob]

I am seeing the same thing. this._keyBindings should have been initialized in the registered callback, but it looks like that doesn't run. However, I don't get this error with all elements that use this. Have not been able to track it down yet.

[dfreedm]

Can you provide an example where this fails? I'm not seeing this behavior by running the tests of <paper-dialog>

[balloob]

I've been trying to recreate a standalone repro and have failed 😞

However, I can give you a repro in our demo that you can check out locally too.

The repro is deployed here: https://repro-a11y--home-assistant-demo.netlify.com

To repro:

• Open dev tools
• Click on top left menu button to show the sidebar
• Click on history

Notes:

• Refreshing page does not trigger it 🤔 requires navigation
• Only the history page triggers it
• Repro possible in Chrome, FF, Safari

If you want to check out the repro locally:

• https://github.com/home-assistant/home-assistant-polymer/tree/repro-a11y
• yarn to install packages
• demo/script/develop_demo to launch the demo
• Visit http://localhost:8080 and follow above repro steps

[dfreedm]

This could be Polymer/polymer@50ad018c

[dfreedm]

Hmm, I see you are extending paper-dropdown-menu here: https://github.com/home-assistant/home-assistant-polymer/blob/repro-a11y/src/components/ha-paper-dropdown-menu.ts

This is probably breaking the registration of paper-dropdown-menu itself somehow.

[dfreedm]

Ok, it looks like in 3.2, we tried to optimize behavior registration to behave more like Polymer 1.x, and mix behaviors onto the element prototype, rather than generating a mixin for every behavior.

However, this breaks your particular use case, because the first element to boot up will have the registered call run on it, which in your case the this subclass of paper-dropdown-menu. This means that the paper-dropdown-menu in the "History" section is missing what was set in registered.

We need to run registered on each subclass of the Polymer({}) generated class, which is more like the 3.1 behavior.