Insert code cell when changing default language (#2031)

lib/livebook_web/live/session_live.ex

@@ -937,18 +937,7 @@ defmodule LivebookWeb.SessionLive do
   end
 
   def handle_event("insert_cell_below", params, socket) do
-    {type, attrs} = cell_type_and_attrs_from_params(params, socket)
+    {:noreply, insert_cell_below(socket, params)}
-
-    with {:ok, section, index} <-
-           section_with_next_index(
-             socket.private.data.notebook,
-             params["section_id"],
-             params["cell_id"]
-           ) do
-      Session.insert_cell(socket.assigns.session.pid, section.id, index, type, attrs)
-    end
-
-    {:noreply, socket}
   end
 
   def handle_event("insert_code_block_below", params, socket) do
@@ -1034,11 +1023,11 @@ defmodule LivebookWeb.SessionLive do
     end
   end
 
-  def handle_event("set_default_language", %{"language" => language}, socket)
+  def handle_event("set_default_language", %{"language" => language} = params, socket)
       when language in ["elixir", "erlang"] do
     language = String.to_atom(language)
     Session.set_notebook_attributes(socket.assigns.session.pid, %{default_language: language})
-    {:noreply, socket}
+    {:noreply, insert_cell_below(socket, params)}
   end
 
   def handle_event("delete_cell", %{"cell_id" => cell_id}, socket) do
@@ -1497,7 +1486,7 @@ defmodule LivebookWeb.SessionLive do
       "url" => url
     }
 
-    handle_event("insert_cell_below", params, socket)
+    {:noreply, insert_cell_below(socket, params)}
   end
 
   def handle_info({:push_patch, to}, socket) do
@@ -1894,12 +1883,28 @@ defmodule LivebookWeb.SessionLive do
     String.upcase(head) <> tail
   end
 
-  defp cell_type_and_attrs_from_params(%{"type" => "markdown"}, _socket), do: {:markdown, %{}}
+  defp insert_cell_below(socket, params) do
+    {type, attrs} = cell_type_and_attrs_from_params(params)
 
-  defp cell_type_and_attrs_from_params(%{"type" => "code"}, socket),
+    with {:ok, section, index} <-
-    do: {:code, %{language: socket.private.data.notebook.default_language}}
+           section_with_next_index(
+             socket.private.data.notebook,
+             params["section_id"],
+             params["cell_id"]
+           ) do
+      Session.insert_cell(socket.assigns.session.pid, section.id, index, type, attrs)
+    end
 
-  defp cell_type_and_attrs_from_params(%{"type" => "diagram"}, _socket) do
+    socket
+  end
+
+  defp cell_type_and_attrs_from_params(%{"type" => "markdown"}), do: {:markdown, %{}}
+
+  defp cell_type_and_attrs_from_params(%{"type" => "code", "language" => language})
+       when language in ["elixir", "erlang"],
+       do: {:code, %{language: String.to_atom(language)}}
+
+  defp cell_type_and_attrs_from_params(%{"type" => "diagram"}) do
     source = """
     <!-- Learn more at https://mermaid-js.github.io/mermaid -->
 
@@ -1915,7 +1920,7 @@ defmodule LivebookWeb.SessionLive do
     {:markdown, %{source: source}}
   end
 
-  defp cell_type_and_attrs_from_params(%{"type" => "image", "url" => url}, _socket) do
+  defp cell_type_and_attrs_from_params(%{"type" => "image", "url" => url}) do
     source = "![](#{url})"
 
     {:markdown, %{source: source}}

lib/livebook_web/live/session_live/insert_buttons_component.ex

@@ -23,9 +23,9 @@ defmodule LivebookWeb.SessionLive.InsertButtonsComponent do
                 class="pr-2"
                 phx-click="insert_cell_below"
                 phx-value-type="code"
+                phx-value-language={@default_language}
                 phx-value-section_id={@section_id}
                 phx-value-cell_id={@cell_id}
-                phx-value-language="elixir"
               >
                 + <%= @default_language |> Atom.to_string() |> String.capitalize() %>
               </div>
@@ -35,13 +35,27 @@ defmodule LivebookWeb.SessionLive.InsertButtonsComponent do
             </button>
           </:toggle>
           <.menu_item>
-            <button role="menuitem" phx-click="set_default_language" phx-value-language="elixir">
+            <button
+              role="menuitem"
+              phx-click="set_default_language"
+              phx-value-type="code"
+              phx-value-language="elixir"
+              phx-value-section_id={@section_id}
+              phx-value-cell_id={@cell_id}
+            >
               <.cell_icon cell_type={:code} language={:elixir} />
               <span>Elixir</span>
             </button>
           </.menu_item>
           <.menu_item>
-            <button role="menuitem" phx-click="set_default_language" phx-value-language="erlang">
+            <button
+              role="menuitem"
+              phx-click="set_default_language"
+              phx-value-type="code"
+              phx-value-language="erlang"
+              phx-value-section_id={@section_id}
+              phx-value-cell_id={@cell_id}
+            >
               <.cell_icon cell_type={:code} language={:erlang} />
               <span>Erlang</span>
             </button>