[minielixir] handle empty cond & other errors (#1473)

Author: fazzone

lib/sequin/consumers/consumers.ex

@@ -1376,6 +1376,9 @@ defmodule Sequin.Consumers do
           []
       end
     end
+  rescue
+    error ->
+      [code: "validation failed: #{Exception.message(error)}"]
   end
 
   def safe_evaluate_code(code) do

lib/sequin/transforms/minielixir/validator.ex

@@ -214,7 +214,9 @@ defmodule Sequin.Transforms.MiniElixir.Validator do
   defp good({:defmodule, _, _}), do: {:error, :validator, "defining modules is not allowed"}
   defp good({:def, _, _}), do: {:error, :validator, "defining functions is not allowed"}
   defp good({:defp, _, _}), do: {:error, :validator, "defining functions is not allowed"}
-  defp good({:cond, _meta, [[{:do, body}]]}), do: check_body(body)
+  defp good({:cond, _meta, [[{:do, body}]]}) when is_list(body), do: check_body(body)
+  # Empty cond has an empty block not an empty list
+  defp good({:cond, _meta, [[{:do, body}]]}), do: check(body)
 
   defp good({:=, _meta, [l, r]}) do
     with {:ok, bound} = __MODULE__.PatternChecker.extract_bound_vars(l) do

test/sequin/minielixir_test.exs

@@ -396,6 +396,16 @@ defmodule Sequin.MiniElixirTest do
                  end
                )
     end
+
+    test "empty cond expression" do
+      assert :ok =
+               Validator.check(
+                 quote do
+                   cond do
+                   end
+                 end
+               )
+    end
   end
 
   defp get_vars(ast) do