Prevent board names with only spaces and show validation message

app/javascript/controllers/form_controller.js

@@ -21,8 +21,13 @@ export default class extends Controller {
 
     if (input) {
       const value = (input.value || "").trim()
-      if (value.length === 0) {
+      const isEmpty = value.length === 0
+
+      if (isEmpty) {
         event.preventDefault()
+        input.setCustomValidity(input.validationMessage || "Please fill out this field")
+        input.reportValidity()
+        input.addEventListener("input", () => input.setCustomValidity(""), { once: true })
       }
     }
   }

app/views/boards/new.html.erb

@@ -1,9 +1,9 @@
 <% @page_title = "Create a new board" %>
 
 <div class="panel panel--centered">
-  <%= form_with model: @board, class: "flex flex-column gap", data: { controller: "form" } do |form| %>
+  <%= form_with model: @board, class: "flex flex-column gap", data: { controller: "form", action: "submit->form#preventEmptySubmit" } do |form| %>
     <h1 class="txt-x-large margin-none font-weight-black"><%= @page_title %></h1>
-    <%= form.text_field :name, required: true, class: "input full-width", autofocus: true, autocomplete: "off",placeholder: "Name it…", data: { action: "keydown.esc@document->form#cancel" } %>
+    <%= form.text_field :name, required: true, class: "input full-width", autofocus: true, autocomplete: "off", placeholder: "Name it…", data: { form_target: "input", action: "keydown.esc@document->form#cancel" } %>
 
     <button type="submit" class="btn btn--link center">
       <span>Create board</span>