String.split("") should be [""], %w() should be []

Author: Devin Torres

lib/elixir/lib/kernel.ex

@@ -3757,6 +3757,8 @@ defmodule Kernel do
     end
   end
 
+  defp split_words("", _modifiers), do: []
+
   defp split_words(string, modifiers) do
     mod = case modifiers do
       [] -> ?b

lib/elixir/lib/string.ex

@@ -246,6 +246,8 @@ defmodule String do
   @spec split(t, t | [t] | Regex.t, Keyword.t) :: [t]
   def split(binary, pattern, options // [])
 
+  def split("", _pattern, _options), do: [""]
+
   def split(binary, pattern, options) when is_regex(pattern) do
     Regex.split(pattern, binary, global: options[:global])
   end

lib/elixir/priv/unicode.ex

@@ -137,7 +137,7 @@ defmodule String.Unicode do
 
   # Split
 
-  def split(""), do: ""
+  def split(""), do: [""]
 
   def split(string) when is_binary(string) do
     :lists.reverse do_split(string, "", [])

lib/elixir/test/elixir/kernel/sigils_test.exs

@@ -50,6 +50,7 @@ defmodule Kernel.SigilsTest do
   end
 
   test :sigil_w do
+    assert %w() == []
     assert %w(foo bar baz) == ["foo", "bar", "baz"]
     assert %w(foo #{:bar} baz) == ["foo", "bar", "baz"]
 

lib/elixir/test/elixir/regex_test.exs

@@ -101,6 +101,7 @@ defmodule Regex.BinaryTest do
   end
 
   test :split do
+    assert Regex.split(%r",", "") == [""]
     assert Regex.split(%r" ", "foo bar baz") == ["foo", "bar", "baz"]
     assert Regex.split(%r" ", "foo bar baz", parts: 2) == ["foo", "bar baz"]
     assert Regex.split(%r"\s", "foobar") == ["foobar"]

lib/elixir/test/elixir/string_test.exs

@@ -16,6 +16,7 @@ defmodule StringTest do
   end
 
   test :split do
+    assert String.split("") == [""]
     assert String.split("foo bar") == ["foo", "bar"]
     assert String.split(" foo bar") == ["foo", "bar"]
     assert String.split("foo bar ") == ["foo", "bar"]
@@ -24,6 +25,7 @@ defmodule StringTest do
     assert String.split("foo" <> <<31>> <> "bar") == ["foo", "bar"]
     assert String.split("foo" <> <<194, 133>> <> "bar") == ["foo", "bar"]
 
+    assert String.split("", ",") == [""]
     assert String.split("a,b,c", ",") == ["a", "b", "c"]
     assert String.split("a,b", ".") == ["a,b"]
     assert String.split("1,2 3,4", [" ", ","]) == ["1", "2", "3", "4"]
@@ -33,6 +35,7 @@ defmodule StringTest do
   end
 
   test :split_with_regex do
+    assert String.split("", %r{,}) == [""]
     assert String.split("a,b", %r{,}) == ["a", "b"]
     assert String.split("a,b,c", %r{,}) == ["a", "b", "c"]
     assert String.split("a,b,c", %r{,}, global: false) == ["a", "b,c"]