Update instructions in the Elixir export (#1144)

lib/livebook/notebook/export/elixir.ex

@@ -15,11 +15,13 @@ defmodule Livebook.Notebook.Export.Elixir do
   defp render_notebook(notebook) do
     %{setup_section: %{cells: [setup_cell]} = setup_section} = notebook
 
+    prelude = "# Run as: iex --dot-iex path/to/notebook.exs"
+
     name = ["# Title: ", notebook.name]
     setup_cell = render_setup_cell(setup_cell, setup_section)
     sections = Enum.map(notebook.sections, &render_section(&1, notebook))
 
-    [name, setup_cell | sections]
+    [prelude, name, setup_cell | sections]
     |> Enum.reject(&is_nil/1)
     |> Enum.intersperse("\n\n")
   end

lib/livebook_web/live/session_live/export_component.ex

@@ -41,7 +41,7 @@ defmodule LivebookWeb.SessionLive.ExportComponent do
           <%= live_patch to: Routes.session_path(@socket, :export, @session.id, "exs"),
                 class: "tab #{if(@tab == "exs", do: "active")}" do %>
             <span class="font-medium">
-              Elixir Script
+              IEx session
             </span>
           <% end %>
         </div>

lib/livebook_web/live/session_live/export_elixir_component.ex

@@ -17,16 +17,6 @@ defmodule LivebookWeb.SessionLive.ExportElixirComponent do
   def render(assigns) do
     ~H"""
     <div class="flex flex-col space-y-6">
-      <p class="text-gray-700">
-        <span class="font-semibold">Note:</span>
-        the script export is available as a convenience, rather than
-        an exact reproduction of the notebook and in some cases it may
-        not even compile. For example, if you define a macro in one cell
-        and import it in another cell, it works fine in Livebook,
-        because each cell is compiled separately. However, when running
-        the script it gets compiled as a whole and consequently doing so
-        doesn't work. Additionally, branching sections are commented out.
-      </p>
       <div class="flex flex-col space-y-1">
         <div class="flex justify-between items-center">
           <span class="text-sm text-gray-700 font-semibold">

test/livebook/notebook/export/elixir_test.exs

@@ -76,6 +76,8 @@ defmodule Livebook.Notebook.Export.ElixirTest do
     }
 
     expected_document = """
+    # Run as: iex --dot-iex path/to/notebook.exs
+
     # Title: My Notebook
 
     # ── Section 1 ──
@@ -117,6 +119,8 @@ defmodule Livebook.Notebook.Export.ElixirTest do
         |> Notebook.put_setup_cell(%{Notebook.Cell.new(:code) | source: "Mix.install([...])"})
 
       expected_document = """
+      # Run as: iex --dot-iex path/to/notebook.exs
+
       # Title: My Notebook
 
       Mix.install([...])

test/livebook_test.exs

@@ -15,6 +15,8 @@ defmodule LivebookTest do
     """
 
     assert Livebook.live_markdown_to_elixir(markdown) == """
+           # Run as: iex --dot-iex path/to/notebook.exs
+
            # Title: Lists
 
            # ── Introduction ──

test/livebook_web/controllers/session_controller_test.exs

@@ -133,6 +133,8 @@ defmodule LivebookWeb.SessionControllerTest do
       assert get_resp_header(conn, "content-type") == ["text/plain"]
 
       assert conn.resp_body == """
+             # Run as: iex --dot-iex path/to/notebook.exs
+
              # Title: Untitled notebook
 
              # ── Section ──