{"action":"created","issue":{"url":"https://api.github.com/repos/Polymer/polymer/issues/1673","labels_url":"https://api.github.com/repos/Polymer/polymer/issues/1673/labels{/name}","comments_url":"https://api.github.com/repos/Polymer/polymer/issues/1673/comments","events_url":"https://api.github.com/repos/Polymer/polymer/issues/1673/events","html_url":"https://github.com/Polymer/polymer/issues/1673","id":82608135,"number":1673,"title":"Can't instantiate component under Shady DOM (where hostAttributes triggers property change handler)","user":{"login":"JanMiksovsky","id":86139,"avatar_url":"https://avatars.githubusercontent.com/u/86139?v=3","gravatar_id":"","url":"https://api.github.com/users/JanMiksovsky","html_url":"https://github.com/JanMiksovsky","followers_url":"https://api.github.com/users/JanMiksovsky/followers","following_url":"https://api.github.com/users/JanMiksovsky/following{/other_user}","gists_url":"https://api.github.com/users/JanMiksovsky/gists{/gist_id}","starred_url":"https://api.github.com/users/JanMiksovsky/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/JanMiksovsky/subscriptions","organizations_url":"https://api.github.com/users/JanMiksovsky/orgs","repos_url":"https://api.github.com/users/JanMiksovsky/repos","events_url":"https://api.github.com/users/JanMiksovsky/events{/privacy}","received_events_url":"https://api.github.com/users/JanMiksovsky/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":5,"created_at":"2015-05-29T22:13:54Z","updated_at":"2015-06-02T23:44:54Z","closed_at":null,"body":"Polymer 1.0 appears to contain a regression from Polymer 0.9. This [gist](https://gist.github.com/JanMiksovsky/16f7f5f2fc5cca95fda1) shows a component that uses hostAttributes to set a property; setting the property triggers a property changed handler.\r\n\r\nThis element cannot be instantiated under Shady DOM. It raises an exception:\r\n\r\n```\r\nTypeError: undefined is not an object (evaluating 'this.__data__[property]')\r\n```\r\n\r\nIt looks like a low-level function called _propertySet is trying to access a property bag called __data__ which has not yet been created.\r\n\r\nCode such as this used to work up to Polymer 0.9.\r\n\r\nThis is probably a small bug somewhere, but it's currently preventing Basic Web Components like [basic-list-box](component.kitchen/components/basic-web-components/basic-list-box) and [basic-carousel](component.kitchen/components/basic-web-components/basic-carousel) from working under Polymer 1.0. We'd obviously like to be able to have those components work with the final 1.0 release."},"comment":{"url":"https://api.github.com/repos/Polymer/polymer/issues/comments/108132961","html_url":"https://github.com/Polymer/polymer/issues/1673#issuecomment-108132961","issue_url":"https://api.github.com/repos/Polymer/polymer/issues/1673","id":108132961,"user":{"login":"kevinpschaaf","id":1354932,"avatar_url":"https://avatars.githubusercontent.com/u/1354932?v=3","gravatar_id":"","url":"https://api.github.com/users/kevinpschaaf","html_url":"https://github.com/kevinpschaaf","followers_url":"https://api.github.com/users/kevinpschaaf/followers","following_url":"https://api.github.com/users/kevinpschaaf/following{/other_user}","gists_url":"https://api.github.com/users/kevinpschaaf/gists{/gist_id}","starred_url":"https://api.github.com/users/kevinpschaaf/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/kevinpschaaf/subscriptions","organizations_url":"https://api.github.com/users/kevinpschaaf/orgs","repos_url":"https://api.github.com/users/kevinpschaaf/repos","events_url":"https://api.github.com/users/kevinpschaaf/events{/privacy}","received_events_url":"https://api.github.com/users/kevinpschaaf/received_events","type":"User","site_admin":false},"created_at":"2015-06-02T23:44:54Z","updated_at":"2015-06-02T23:44:54Z","body":"Thanks for bearing with me-- glad you're unblocked.  Understanding the use case and available workarounds helps set priority.  We took a quick look today and it is related to differences in polyfill timing of `attributeChanged` when nested inside `createdCallback` -- the fix will likely be in the polyfill."}}