App and root layout are split because LV, or more specifically morphdom on the client, shouldn’t try to mess with any markup outside of <body>. And even more so you don’t want to apply the root layout twice, which might be the case here as well, unless you removed the application of the :root layout as a root_layout.
LostKobrakai
1
jberling
Ok, good to know.
This is a major footgun. I lost two days because of this. And nearly ditched LiveView and Phoenix out of frustration, even though I’m really pleased with both LiveView and Phoenix otherwise!
0
FlyingNoodle
jberling
Great!
But if you accidentally do what I did, change the layout to :root, it will take a long time to understand why your state behaves so strangely, at least for me.
I created a simple PR in the Phoenix repository. More intelligent people might have better solutions, but at least I’ve made an effort to contribute instead of just whining 
0
steffend
Phoenix Core Team
The behavior is indeed interesting. What’s going on is that the app.js is executed twice, because it is included twice in the initial render. That causes two LiveViews to be started that both try to control the same DOM and causing a lot of chaos. I’ll think about ways to make that fail in a more obvious way 
3
jberling
That explains a lot!
I saw two processes in LiveDebugger, which I thought was strange, but since it was the first time I used the tool, I thought one could be related to dev tools or something.
0
steffend
Phoenix Core Team
We should have some kind of warning in the future: complain loudly if LV is initialized twice by SteffenDE · Pull Request #3721 · phoenixframework/phoenix_live_view · GitHub
7
jberling
Love it! That’s a nice and clean solution. It would have saved me lots of time and energy!
1