Show helpful message when uploading duplicate firmware

lib/nerves_hub_web/live/firmware.ex

@@ -140,6 +140,16 @@ defmodule NervesHubWeb.Live.Firmware do
        }} ->
         error_feedback(socket, "No matching product could be found.")
 
+      {:error,
+       %Ecto.Changeset{
+         errors: [
+           uuid:
+             {"has already been taken",
+              [constraint: :unique, constraint_name: "firmwares_product_id_uuid_index"]}
+         ]
+       } = changeset} ->
+        error_feedback(socket, changeset)
+
       {:error, %Ecto.Changeset{}} ->
         error_feedback(socket, "Unknown error uploading firmware.")
 
@@ -151,6 +161,20 @@ defmodule NervesHubWeb.Live.Firmware do
     end
   end
 
+  defp error_feedback(
+         socket,
+         %Ecto.Changeset{errors: [uuid: {"has already been taken", _}]} = changeset
+       ) do
+    socket
+    |> assign(:error_message, "Duplicate Firmware Is Not Allowed")
+    |> assign(:error_code, :duplicate_firmware)
+    |> assign(
+      :firmware_path,
+      "/org/#{socket.assigns.org.name}/#{socket.assigns.product.name}/firmware/#{changeset.changes.uuid}"
+    )
+    |> noreply()
+  end
+
   defp error_feedback(socket, %Ecto.Changeset{} = changeset) do
     error_message =
       changeset.errors

lib/nerves_hub_web/live/firmware_templates/upload_firmware_template.html.heex

@@ -9,7 +9,14 @@
     <.live_file_input upload={@uploads.firmware} required />
 
     <div class="has-error">
-      <span :if={@error_message} class="help-block"><%= @error_message %></span>
+      <span :if={@error_message} class="help-block">
+        <%= case @error_code do %>
+          <% :duplicate_firmware -> %>
+            <%= @error_message %> <a href={@firmware_path} target="_blank">View Firmware</a>
+          <% _ -> %>
+            <%= @error_message %>
+        <% end %>
+      </span>
     </div>
 
     <div :for={entry <- @uploads.firmware.entries} class="mt-1">