Add warning on export page if there are stale output

lib/livebook_web/live/session_live.ex

@@ -614,6 +614,7 @@ defmodule LivebookWeb.SessionLive do
         id="export"
         session={@session}
         tab={@tab}
+        any_stale_cell?={@any_stale_cell?}
       />
     </.modal>
 
@@ -1059,7 +1060,8 @@ defmodule LivebookWeb.SessionLive do
   end
 
   def handle_params(%{"tab" => tab}, _url, socket) when socket.assigns.live_action == :export do
-    {:noreply, assign(socket, tab: tab)}
+    any_stale_cell? = any_stale_cell?(socket.private.data)
+    {:noreply, assign(socket, tab: tab, any_stale_cell?: any_stale_cell?)}
   end
 
   def handle_params(%{"tab" => tab} = params, _url, socket)
@@ -2964,4 +2966,12 @@ defmodule LivebookWeb.SessionLive do
 
   defp intellisense_node(%Cell.Smart{editor_intellisense_node: node_cookie}), do: node_cookie
   defp intellisense_node(_), do: nil
+
+  defp any_stale_cell?(data) do
+    data.notebook
+    |> Notebook.evaluable_cells_with_section()
+    |> Enum.any?(fn {cell, _section} ->
+      data.cell_infos[cell.id].eval.validity == :stale
+    end)
+  end
 end

lib/livebook_web/live/session_live/export_component.ex

@@ -5,19 +5,15 @@ defmodule LivebookWeb.SessionLive.ExportComponent do
 
   @impl true
   def update(assigns, socket) do
+    {any_stale_cell?, assigns} = Map.pop!(assigns, :any_stale_cell?)
     socket = assign(socket, assigns)
 
-    socket =
-      if socket.assigns[:notebook] do
-        socket
-      else
-        # Note: we need to load the notebook, because the local data
-        # has cell contents stripped out
-        notebook = Session.get_notebook(socket.assigns.session.pid)
-        assign(socket, :notebook, notebook)
-      end
-
-    {:ok, socket}
+    {:ok,
+     socket
+     # Note: we need to load the notebook, because the local data
+     # has cell contents stripped out
+     |> assign_new(:notebook, fn -> Session.get_notebook(socket.assigns.session.pid) end)
+     |> assign_new(:any_stale_cell?, fn -> any_stale_cell? end)}
   end
 
   @impl true
@@ -55,6 +51,7 @@ defmodule LivebookWeb.SessionLive.ExportComponent do
             id={"export-notebook-#{@tab}"}
             session={@session}
             notebook={@notebook}
+            any_stale_cell?={@any_stale_cell?}
           />
         </div>
       </div>

lib/livebook_web/live/session_live/export_live_markdown_component.ex

@@ -31,6 +31,11 @@ defmodule LivebookWeb.SessionLive.ExportLiveMarkdownComponent do
           <.switch_field name="include_outputs" label="Include outputs" value={@include_outputs} />
         </form>
       </div>
+      <.message_box
+        :if={@include_outputs and @any_stale_cell?}
+        kind={:warning}
+        message="There are stale cells, some outputs may be inaccurate."
+      />
       <div class="flex flex-col space-y-1">
         <div class="flex justify-between items-center">
           <span class="text-sm text-gray-700 font-semibold">