Bump to v4.9.0.

split.js

@@ -1,5 +1,19 @@
+import isRegExp from './isRegExp';
+import stringToArray from './_stringToArray';
 import toString from './toString';
 
+/** Used to compose unicode character classes. */
+var rsAstralRange = '\\ud800-\\udfff',
+    rsComboMarksRange = '\\u0300-\\u036f\\ufe20-\\ufe23',
+    rsComboSymbolsRange = '\\u20d0-\\u20f0',
+    rsVarRange = '\\ufe0e\\ufe0f';
+
+/** Used to compose unicode capture groups. */
+var rsZWJ = '\\u200d';
+
+/** Used to detect strings with [zero-width joiners or code points from the astral planes](http://eev.ee/blog/2015/09/12/dark-corners-of-unicode/). */
+var reHasComplexSymbol = RegExp('[' + rsZWJ + rsAstralRange  + rsComboMarksRange + rsComboSymbolsRange + rsVarRange + ']');
+
 /**
  * Splits `string` by `separator`.
  *
@@ -20,7 +34,18 @@ import toString from './toString';
  * // => ['a', 'b']
  */
 function split(string, separator, limit) {
-  return toString(string).split(separator, limit);
+  string = toString(string);
+  if (string && (
+        typeof separator == 'string' ||
+        (separator != null && !isRegExp(separator))
+      )) {
+    separator += '';
+    if (separator == '' && reHasComplexSymbol.test(string)) {
+      var strSymbols = stringToArray(string);
+      return limit === undefined ? strSymbols : strSymbols.slice(0, limit < 0 ? 0 : limit);
+    }
+  }
+  return string.split(separator, limit);
 }
 
 export default split;