From 3af8aa158c05dd40c6b469d7221667b842d64a48 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fabian=20N=2EC=2E=20van=20=C2=B4t=20Hooft?=
 <fabian.vanthooft@ekinops.com>
Date: Wed, 19 Jul 2023 14:00:47 -0300
Subject: [PATCH] Add erlang-module support

The code is deemed a module definition if the first line
start with "-module(".

In this case the entire code-block is interpreted as
erlang-module and if there are no errors the module is compiled
and loaded.
---
 lib/livebook/runtime/evaluator.ex | 41 +++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/lib/livebook/runtime/evaluator.ex b/lib/livebook/runtime/evaluator.ex
index 7043eb5b7021..5781857a5047 100644
--- a/lib/livebook/runtime/evaluator.ex
+++ b/lib/livebook/runtime/evaluator.ex
@@ -675,6 +675,47 @@ defmodule Livebook.Runtime.Evaluator do
   end
 
   defp eval(:erlang, code, binding, env) do
+    is_module = String.starts_with?(code, "-module(")
+
+    case is_module do
+      true -> eval_module(:erlang, code, binding, env)
+      false -> eval_statements(:erlang, code, binding, env)
+    end
+  end
+
+  # Create module - tokens from string
+  # Based on: https://stackoverflow.com/questions/2160660/how-to-compile-erlang-code-loaded-into-a-string
+  # The function will first assume that code starting with -module( is a erlang module definition
+
+  # Step 1: Split the module in \n
+  # Step 2: Scan and convert to froms
+  # Step 3: Extract module name
+  # Step 4: Compile and load
+  defp eval_module(:erlang, code, binding, env) do
+    statements = :binary.split(code, "\n", [:global, :trim_all])
+
+    forms =
+      Enum.map(
+        statements,
+        fn str ->
+          {:ok, result, _} = :erl_scan.string(String.to_charlist(str))
+          {:ok, form} = :erl_parse.parse_form(result)
+          form
+        end
+      )
+
+    # First statement - form = module definition
+    {:attribute, 1, :module, module_name} = hd(forms)
+
+    # Compile froms to binary
+    {:ok, _, binary_module} = :compile.forms(forms)
+
+    :code.load_binary(module_name, ~c"nofile", binary_module)
+
+    {{:ok, ~c"erlang module successfully compiled", binding, env}, []}
+  end
+
+  defp eval_statements(:erlang, code, binding, env) do
     try do
       erl_binding =
         Enum.reduce(binding, %{}, fn {name, value}, erl_binding ->