Handle Task::NotFoundError with a 404 page instead of raising an error

app/controllers/maintenance_tasks/application_controller.rb

@@ -31,5 +31,9 @@ class ApplicationController < MaintenanceTasks.parent_controller.constantize
     end
 
     protect_from_forgery with: :exception
+
+    rescue_from Task::NotFoundError do |error|
+      render("maintenance_tasks/not_found", status: :not_found)
+    end
   end
 end

app/views/maintenance_tasks/not_found.html.erb

@@ -0,0 +1,9 @@
+<% content_for :page_title, "Not Found" %>
+
+<div class="container has-text-centered">
+  <h1 class="title is-3 has-text-weight-bold">Task Not Found</h1>
+  <p class="subtitle is-5">The task you are looking for does not exist or has been deleted.</p>
+  <p>
+    <%= link_to "Back to Tasks", tasks_path, class: "button is-primary is-rounded" %>
+  </p>
+</div>

lib/maintenance_tasks/engine.rb

@@ -32,9 +32,5 @@ class Engine < ::Rails::Engine
     config.after_initialize do
       JobIteration.max_job_runtime ||= 5.minutes
     end
-
-    config.action_dispatch.rescue_responses.merge!(
-      "MaintenanceTasks::Task::NotFoundError" => :not_found,
-    )
   end
 end

test/system/maintenance_tasks/tasks_test.rb

@@ -259,6 +259,16 @@ class TasksTest < ApplicationSystemTestCase
       assert_button "Run", disabled: true
     end
 
+    test "show a not found Task" do
+      visit maintenance_tasks_path + "/tasks/Maintenance::DoesNotExist"
+
+      assert_title "Not Found"
+      assert_includes page.driver.browser.logs.get(:browser).sole.message, "404"
+      assert_text "Task Not Found"
+      assert_text "The task you are looking for does not exist or has been deleted."
+      assert_link "Back to Tasks"
+    end
+
     test "visit main page through iframe" do
       visit root_path