From f08fe63042b1c28fd5e289e73e780c2e9b504e89 Mon Sep 17 00:00:00 2001
From: Tobi Lutke <tobi@shopify.com>
Date: Wed, 11 Mar 2026 10:20:11 -0400
Subject: [PATCH] =?UTF-8?q?Replace=20split+join=20in=20truncatewords=20wit?=
 =?UTF-8?q?h=20manual=20word=20scan=20=E2=80=94=20avoids=20array=20+=20str?=
 =?UTF-8?q?ing=20allocations\n\nResult:=20{"status":"keep","combined=5F?=
 =?UTF-8?q?=C2=B5s":4280,"parse=5F=C2=B5s":3009,"render=5F=C2=B5s":1271,"a?=
 =?UTF-8?q?llocations":26395}?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 lib/liquid/standardfilters.rb | 58 ++++++++++++++++++++++++++++-------
 1 file changed, 47 insertions(+), 11 deletions(-)

diff --git a/lib/liquid/standardfilters.rb b/lib/liquid/standardfilters.rb
index ed614156..4cbdc8ed 100644
--- a/lib/liquid/standardfilters.rb
+++ b/lib/liquid/standardfilters.rb
@@ -275,18 +275,54 @@ module Liquid
       words = Utils.to_integer(words)
       words = 1 if words <= 0
 
-      wordlist = begin
-        input.split(" ", words + 1)
-      rescue RangeError
-        # integer too big for String#split, but we can semantically assume no truncation is needed
-        return input if words + 1 > MAX_I32
-        raise # unexpected error
-      end
-      return input if wordlist.length <= words
+      return input if words + 1 > MAX_I32
 
-      wordlist.pop
-      truncate_string = Utils.to_s(truncate_string)
-      wordlist.join(" ").concat(truncate_string)
+      # Build result incrementally — avoids split() array + string allocations
+      len = input.bytesize
+      pos = 0
+      word_count = 0
+      result = nil
+
+      # Skip leading whitespace
+      while pos < len
+        b = input.getbyte(pos)
+        break unless b == 32 || b == 9 || b == 10 || b == 13 || b == 12
+        pos += 1
+      end
+
+      while pos < len
+        word_start = pos
+        word_count += 1
+
+        # Skip non-whitespace chars (word body)
+        while pos < len
+          b = input.getbyte(pos)
+          break if b == 32 || b == 9 || b == 10 || b == 13 || b == 12
+          pos += 1
+        end
+
+        if word_count > words
+          # Truncate — result already has the first N words
+          truncate_string = Utils.to_s(truncate_string)
+          return result.concat(truncate_string)
+        end
+
+        # Append word to result (only allocate result when we know truncation is possible)
+        if result
+          result << " " << input.byteslice(word_start, pos - word_start)
+        else
+          result = +input.byteslice(word_start, pos - word_start)
+        end
+
+        # Skip whitespace between words
+        while pos < len
+          b = input.getbyte(pos)
+          break unless b == 32 || b == 9 || b == 10 || b == 13 || b == 12
+          pos += 1
+        end
+      end
+
+      input
     end
 
     # @liquid_public_docs