Fix saving notebook to S3 file system (#3134)

Author: hugobarauna

lib/livebook/file_system/s3.ex

@@ -22,6 +22,8 @@ defmodule Livebook.FileSystem.S3 do
           token: String.t() | nil
         }
 
+  @derive {Inspect, except: [:access_key_id, :secret_access_key]}
+
   embedded_schema do
     field :bucket_url, :string
     field :external_id, :string

lib/livebook_web/live/session_live/persistence_component.ex

@@ -11,6 +11,11 @@ defmodule LivebookWeb.SessionLive.PersistenceComponent do
   end
 
   @impl true
+  def update(%{event: {:mount_file_system, file_system}}, socket) do
+    :ok = FileSystem.mount(file_system)
+    {:ok, socket}
+  end
+
   def update(%{event: {:set_file, file, _info}}, socket) do
     current_file = socket.assigns.draft_file
 

test/livebook_web/live/session_live_test.exs

@@ -1612,6 +1612,21 @@ defmodule LivebookWeb.SessionLiveTest do
       refute render(view) =~ new_dir.path
       assert render(view) =~ old_dir.path
     end
+
+    test "switching to S3 file system in persistence dialog does not crash",
+         %{conn: conn, session: session} do
+      s3_fs = build(:fs_s3)
+      Livebook.HubHelpers.persist_file_system(s3_fs)
+
+      {:ok, view, _} = live(conn, ~p"/sessions/#{session.id}/settings/file")
+
+      view
+      |> element(~s{button[phx-click="set_file_system"][phx-value-id="#{s3_fs.id}"]})
+      |> render_click()
+
+      # The component should handle the mount_file_system event without crashing
+      assert render(view) =~ "Save to file"
+    end
   end
 
   describe "completion" do