From b0c9f576afa9749a12aa0f604d41d46fc4d94d2e Mon Sep 17 00:00:00 2001
From: Tobi Lutke <tobi@shopify.com>
Date: Wed, 11 Mar 2026 09:18:35 -0400
Subject: [PATCH] =?UTF-8?q?REVERTED:=20Cursor=20for=20For=20tag=20adds=201?=
 =?UTF-8?q?48=20allocs=20from=20scan=5Fid/scan=5Ffragment=20string=20creat?=
 =?UTF-8?q?ion\n\nResult:=20{"status":"discard","combined=5F=C2=B5s":5049,?=
 =?UTF-8?q?"parse=5Fus":3765,"render=5Fus":1284,"allocations":29793,"parse?=
 =?UTF-8?q?=5F=C2=B5s":3765,"render=5F=C2=B5s":1284}?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 lib/liquid/cursor.rb | 45 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/lib/liquid/cursor.rb b/lib/liquid/cursor.rb
index 13eba7c2..753c7a9d 100644
--- a/lib/liquid/cursor.rb
+++ b/lib/liquid/cursor.rb
@@ -300,5 +300,50 @@ module Liquid
       return nil unless eos? # trailing junk
       true
     end
+    # ── For tag parser ────────────────────────────────────────────────
+    # Results from parse_for_markup
+    attr_reader :for_var, :for_collection, :for_reversed
+
+    # Parse "var in collection [reversed] [limit:N] [offset:N]"
+    # Returns true on success, nil on failure.
+    def parse_for_markup
+      skip_ws
+      @for_var = scan_id
+      return nil unless @for_var
+
+      skip_ws
+      # expect "in"
+      return nil unless scan_id == "in"
+
+      skip_ws
+      # Collection: parenthesized range or fragment
+      if peek_byte == LPAREN
+        start = @ss.pos
+        depth = 1
+        @ss.scan_byte
+        while !@ss.eos? && depth > 0
+          b = @ss.scan_byte
+          depth += 1 if b == LPAREN
+          depth -= 1 if b == RPAREN
+        end
+        @for_collection = @source.byteslice(start, @ss.pos - start)
+      else
+        @for_collection = scan_fragment
+        return nil unless @for_collection
+      end
+
+      skip_ws
+      # Check for 'reversed'
+      saved = @ss.pos
+      word = scan_id
+      if word == "reversed"
+        @for_reversed = true
+      else
+        @for_reversed = false
+        @ss.pos = saved if word # rewind if we consumed a non-'reversed' word
+      end
+
+      true
+    end
   end
 end