More tests for malformed sequences

Author: josevalim

lib/elixir/lib/string.ex

@@ -524,10 +524,11 @@ defmodule String do
   defp parts_to_index(n) when is_integer(n) and n > 0, do: n
 
   defp split_empty("", true, 1), do: []
-  defp split_empty(string, _, 1) when is_binary(string), do: [IO.iodata_to_binary(string)]
+  defp split_empty(string, _, 1), do: [IO.iodata_to_binary(string)]
 
   defp split_empty(string, trim, count) do
     case :unicode_util.gc(string) do
+      [gc] -> [grapheme_to_binary(gc) | split_empty("", trim, 1)]
       [gc | rest] -> [grapheme_to_binary(gc) | split_empty(rest, trim, count - 1)]
       [] -> split_empty("", trim, 1)
       {:error, <<byte, rest::bits>>} -> [<<byte>> | split_empty(rest, trim, count - 1)]

lib/elixir/test/elixir/string_test.exs

@@ -115,6 +115,9 @@ defmodule StringTest do
              ["", <<225, 158, 128, 225, 158, 185, 225>>]
 
     assert String.split(<<225, 158, 128, 225, 158, 185, 225>>, "", parts: 3) ==
+             ["", "កឹ", <<225>>]
+
+    assert String.split(<<225, 158, 128, 225, 158, 185, 225>>, "", parts: 4) ==
              ["", "កឹ", <<225>>, ""]
   end