performance: Use split limit in truncatewords (#1361)

lib/liquid/standardfilters.rb

@@ -89,13 +89,15 @@ module Liquid
 
     def truncatewords(input, words = 15, truncate_string = "...")
       return if input.nil?
-      wordlist = input.to_s.split
+      input = input.to_s
-      words    = Utils.to_integer(words)
+      words = Utils.to_integer(words)
+      words = 1 if words <= 0
 
-      l = words - 1
+      wordlist = input.split(" ", words + 1)
-      l = 0 if l < 0
+      return input if wordlist.length <= words
 
-      wordlist.length > l ? wordlist[0..l].join(" ").concat(truncate_string.to_s) : input
+      wordlist.pop
+      wordlist.join(" ").concat(truncate_string.to_s)
     end
 
     # Split input string into an array of substrings separated by given pattern.

test/integration/standard_filter_test.rb

@@ -175,6 +175,9 @@ class StandardFiltersTest < Minitest::Test
     )
     assert_equal("测试测试测试测试", @filters.truncatewords('测试测试测试测试', 5))
     assert_equal('one two1', @filters.truncatewords("one two three", 2, 1))
+    assert_equal('one two three...', @filters.truncatewords("one  two\tthree\nfour", 3))
+    assert_equal('one two...', @filters.truncatewords("one two three four", 2))
+    assert_equal('one...', @filters.truncatewords("one two three four", 0))
   end
 
   def test_strip_html