From b06087fdcfc51d39fcaa73cd6813eb573251d87f Mon Sep 17 00:00:00 2001
From: st0012 <stan001212@gmail.com>
Date: Sun, 14 Jun 2026 17:29:07 +0100
Subject: [PATCH] Avoid detecting encoding comments in documentation text

---
 lib/rdoc/encoding.rb            | 6 +++---
 test/rdoc/rdoc_encoding_test.rb | 9 +++++++++
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/lib/rdoc/encoding.rb b/lib/rdoc/encoding.rb
index 78dbe87d0c..735bc4d326 100644
--- a/lib/rdoc/encoding.rb
+++ b/lib/rdoc/encoding.rb
@@ -7,13 +7,13 @@
 
 module RDoc::Encoding
 
-  HEADER_REGEXP = /^
+  HEADER_REGEXP = /\A
     (?:
-      \A\#!.*\n
+      \#!.*\n
       |
       ^\#\s+frozen[-_]string[-_]literal[=:].+\n
       |
-      ^\#[^\n]+\b(?:en)?coding[=:]\s*(?<name>[^\s;]+).*\n
+      ^\#\s*(?:-\*-\s*(?:[^;\n]*;\s*)*)?(?:en)?coding[=:]\s*(?<name>[^:\s;]+).*\n
       |
       <\?xml[^?]*encoding=(?<quote>["'])(?<name>.*?)\k<quote>.*\n
     )+
diff --git a/test/rdoc/rdoc_encoding_test.rb b/test/rdoc/rdoc_encoding_test.rb
index 4a264f5efb..9003a2f9ee 100644
--- a/test/rdoc/rdoc_encoding_test.rb
+++ b/test/rdoc/rdoc_encoding_test.rb
@@ -155,6 +155,15 @@ def test_class_detect_encoding
     assert_equal Encoding::UTF_8, encoding
   end
 
+  def test_class_detect_encoding_ignores_documentation_comments
+    document = "# This document describes a method named #encoding: Returns an object.\n" \
+               "#     Encoding::US_ASCII.name # => \"US-ASCII\"\n" \
+               "# This is a documentation paragraph.\n" \
+               "# coding: UTF-8 is example text, not a magic comment.\n"
+
+    assert_nil RDoc::Encoding.detect_encoding document
+  end
+
   def test_class_set_encoding_bad
     s = ""
     encoding = RDoc::Encoding.detect_encoding s