FIX an issue when re-rendering lit-html elements after rendering a non-lit-html element

[ndelangen]

Issue: #5852

It seems the mountNode becomes stateful after a render has occurred in lit-html.
Since storybook is changing the dom beyond lit-html, it gets "confused" and throws an error because it's unable to remove
some nodes. I guess it's trying to do reconciliation or cleanup, and it's missing state or it's state is inconsistent
with the actual dom.

By adding a extra inner root node that gets reset when switching stories we make lit-html mount correctly

What I did

I changed the render code of app/polymer to reset the dom (harder) when switching to a lit-html element.

[vercel]

This pull request is automatically deployed with Now.
To access deployments, click Details below or on the icon next to each push.

[codecov]

Codecov Report

Merging #5868 into next will decrease coverage by 0.01%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##             next    #5868      +/-   ##
==========================================
- Coverage   35.01%   34.99%   -0.02%     
==========================================
  Files         648      648              
  Lines        9480     9483       +3     
  Branches     1360     1334      -26     
==========================================
  Hits         3319     3319              
- Misses       5532     5534       +2     
- Partials      629      630       +1

Impacted Files	Coverage Δ
app/polymer/src/client/preview/render.js	0% <0%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 3176058...661481a. Read the comment docs.

[codecov]

Codecov Report

Merging #5868 into next will decrease coverage by <.01%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##             next    #5868      +/-   ##
==========================================
- Coverage   34.93%   34.92%   -0.01%     
==========================================
  Files         648      648              
  Lines        9516     9518       +2     
  Branches     1352     1352              
==========================================
  Hits         3324     3324              
- Misses       5575     5576       +1     
- Partials      617      618       +1

Impacted Files	Coverage Δ
app/polymer/src/client/preview/render.js	0% <0%> (ø)	⬆️
addons/a11y/src/components/Report/Item.tsx	0% <0%> (ø)	⬆️
addons/viewport/src/Tool.js	0% <0%> (ø)	⬆️
addons/a11y/src/components/Report/Rules.tsx	0% <0%> (ø)	⬆️
addons/a11y/src/index.ts	0% <0%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update acb1555...68b6009. Read the comment docs.

[daKmoR]

I can confirm that this fixes #5852

any chance this can be released? or is there anything else to do?

[daKmoR]

woop woop thxxxx :)