add MaintainAttrs hook

assets/js/app.js

@@ -25,9 +25,13 @@ import 'phoenix_html'
 import { Socket } from 'phoenix'
 import { LiveSocket } from 'phoenix_live_view'
 import topbar from '../vendor/topbar'
+import MaintainAttrs from './maintain_attrs'
 
 const csrfToken = document.querySelector("meta[name='csrf-token']").getAttribute('content')
-const liveSocket = new LiveSocket('/live', Socket, { params: { _csrf_token: csrfToken } })
+const liveSocket = new LiveSocket('/live', Socket, {
+  params: { _csrf_token: csrfToken },
+  hooks: { MaintainAttrs }
+})
 
 // Show progress bar on live navigation and form submits
 topbar.config({ barColors: { 0: '#29d' }, shadowColor: 'rgba(0, 0, 0, .3)' })

assets/js/maintain_attrs.js

@@ -0,0 +1,8 @@
+// maintain user adjusted attributes, like textbox length on phoenix liveview
+// update. https://github.com/phoenixframework/phoenix_live_view/issues/1011
+
+export default {
+  attrs(){ return this.el.getAttribute("data-attrs").split(", ") },
+  beforeUpdate(){ this.prevAttrs = this.attrs().map(name => [name, this.el.getAttribute(name)]) },
+  updated(){ this.prevAttrs.forEach(([name, val]) => this.el.setAttribute(name, val)) }
+}