Merge pull request #4247 from stephenmoloney/rstrip-bug

String.replace_trailing bug fix.

Author: josevalim

lib/elixir/lib/string.ex

@@ -661,7 +661,7 @@ defmodule String do
     replace_trailing(string, match, replacement, prefix_size, suffix_size, "")
   end
 
-  defp replace_trailing(string, match, replacement, prefix_size, suffix_size, acc) when prefix_size > 0 do
+  defp replace_trailing(string, match, replacement, prefix_size, suffix_size, acc) when prefix_size >= 0 do
     case string do
       <<prefix::size(prefix_size)-binary, suffix::size(suffix_size)-binary>> when suffix == match ->
         replace_trailing(prefix, match, replacement, prefix_size - suffix_size, suffix_size, acc <> replacement)

lib/elixir/test/elixir/string_test.exs

@@ -160,6 +160,17 @@ defmodule StringTest do
     assert String.capitalize("fin") == "Fin"
   end
 
+  test "replace_trailing" do
+    assert String.replace_trailing("   abc aa", "a", "") == "   abc "
+    assert String.replace_trailing("   abc __", "_", "") == "   abc "
+    assert String.replace_trailing(" aaaaaaaaa", "a", "") == " "
+    assert String.replace_trailing("aaaaaaaaaa", "a", "") == ""
+    assert String.replace_trailing("]]]]]]]]]]", "]", "") == ""
+    assert String.replace_trailing("   cat 猫猫", "猫", "") == "   cat "
+    assert String.replace_trailing("test", "t", "") == "tes"
+    assert String.replace_trailing("t", "t", "") == ""
+  end
+
   test "rstrip" do
     assert String.rstrip("") == ""
     assert String.rstrip("1\n") == "1"
@@ -172,6 +183,9 @@ defmodule StringTest do
     assert String.rstrip("a  abc  a" <> <<194, 133>>) == "a  abc  a"
     assert String.rstrip("   abc aa", ?a) == "   abc "
     assert String.rstrip("   abc __", ?_) == "   abc "
+    assert String.rstrip(" aaaaaaaaa", ?a) == " "
+    assert String.rstrip("aaaaaaaaaa", ?a) == ""
+    assert String.rstrip("]]]]]]]]]]", ?]) == ""
     assert String.rstrip("   cat 猫猫", ?猫) == "   cat "
   end