Allow downloading source from sessions list (#980)

* Support downloading source on a per session basis

* Update session_list_component.ex

* Add test

* Update lib/livebook_web/live/home_live/session_list_component.ex

* Update test/livebook_web/live/home_live_test.exs

Co-authored-by: José Valim <jose.valim@gmail.com>
Co-authored-by: Jonatan Kłosko <jonatanklosko@gmail.com>

lib/livebook_web/live/home_live/session_list_component.ex

@@ -136,6 +136,13 @@ defmodule LivebookWeb.HomeLive.SessionListComponent do
               </button>
             </:toggle>
             <:content>
+              <a class="menu-item text-gray-500"
+                role="menuitem"
+                href={Routes.session_path(@socket, :download_source, session.id, "livemd", include_outputs: false)}
+                download>
+                <.remix_icon icon="download-2-line" class="text-lg"/>
+                <span class="font-medium">Download source</span>
+              </a>
               <button class="menu-item text-gray-500"
                 type="button"
                 role="menuitem"

test/livebook_web/live/home_live_test.exs

@@ -136,6 +136,23 @@ defmodule LivebookWeb.HomeLiveTest do
       refute render(view) =~ id
     end
 
+    test "allows download the source of an existing session", %{conn: conn} do
+      {:ok, session} = Sessions.create_session()
+      Session.set_notebook_name(session.pid, "My notebook")
+
+      {:ok, view, _} = live(conn, "/")
+
+      {:error, {:redirect, %{to: to}}} =
+        view
+        |> element(~s{[data-test-session-id="#{session.id}"] a}, "Download source")
+        |> render_click
+
+      assert to ==
+               Routes.session_path(conn, :download_source, session.id, "livemd",
+                 include_outputs: false
+               )
+    end
+
     test "allows forking existing session", %{conn: conn} do
       {:ok, session} = Sessions.create_session()
       Session.set_notebook_name(session.pid, "My notebook")