fix parsing nested comment tag with extra strings

lib/liquid/tags/comment.rb

@@ -15,7 +15,7 @@ module Liquid
   #   {% endcomment %}
   # @liquid_syntax_keyword content The content of the comment.
   class Comment < Block
-    TagDelimiter = /\A(.*)#{TagStart}#{WhitespaceControl}?\s*(endcomment)\s*(.*)?#{WhitespaceControl}?#{TagEnd}\z/om
+    TAG_DELIMITER = /\A(.*)#{TagStart}#{WhitespaceControl}?\s*(endcomment)\s*(.*)?#{WhitespaceControl}?#{TagEnd}\z/om
 
     def render_to_output_buffer(_context, output)
       output
@@ -51,9 +51,12 @@ module Liquid
             next if tag_name_match.nil?
 
             tag_name_match[1]
-          elsif TagDelimiter.match?(token)
+          elsif TAG_DELIMITER.match?(token)
-            # aggressively match comment delimiter first
+            # aggressively match comment delimiter
             "endcomment"
+          elsif token =~ BlockBody::FullToken && Regexp.last_match(2) == "comment"
+            # aggressively match comment tag
+            "comment"
           else
             tag_name_match = BlockBody::FullTokenPossiblyInvalid.match(token)
 

test/unit/tags/comment_tag_unit_test.rb

@@ -121,4 +121,18 @@ class CommentTagUnitTest < Minitest::Test
       LIQUID
     )
   end
+
+  def test_nested_comment_tag_with_extra_strings
+    assert_template_result(
+      '',
+      <<~LIQUID.chomp,
+        {% comment %}
+          {% comment
+            {% assign foo = 1 %}
+          {% endcomment
+          {% assign foo = 1 %}
+        {% endcomment %}
+      LIQUID
+    )
+  end
 end