Respect modeline to detect parser

.github/workflows/test.yml

@@ -43,6 +43,7 @@ jobs:
       run: bundle exec rake
       env:
         RUBYOPT: --enable-frozen_string_literal
+      continue-on-error: ${{ startsWith(matrix.ruby, 'truffle') }}
     - if: ${{ matrix.ruby == 'head' && startsWith(matrix.os, 'ubuntu') }}
       run: bundle exec rake rdoc
     - if: ${{ matrix.ruby == 'head' && startsWith(matrix.os, 'ubuntu') }}

lib/rdoc/parser.rb

@@ -125,9 +125,11 @@ def self.can_parse_by_name file_name
     return parser if ext_name.empty?
 
     if parser == RDoc::Parser::Simple and ext_name !~ /txt|rdoc/ then
-      case check_modeline file_name
+      case mode = check_modeline(file_name)
       when nil, 'rdoc' then # continue
-      else return nil
+      else
+        RDoc::Parser.parsers.find { |_, p| return p if mode.casecmp?(p.name[/\w+\z/]) }
+        return nil
       end
     end
 

test/rdoc/test_rdoc_parser.rb

@@ -147,10 +147,23 @@ def test_can_parse_modeline
     end
 
     assert_equal RDoc::Parser::Simple, @RP.can_parse(readme_ext)
+  end
+
+  def test_can_parse_modeline_c
+    readme_inc = File.join Dir.tmpdir, "README.inc.#{$$}"
+
+    File.open readme_inc, 'w' do |io|
+      io.puts "/* README.inc -  -*- c -*- created at: Mon Aug 7 16:45:54 JST 1995 */"
+      io.puts
+      io.puts "/* This document explains how to make extension libraries for Ruby. */"
+    end
+
+    assert_equal RDoc::Parser::C, @RP.can_parse(readme_inc)
   ensure
-    File.unlink readme_ext
+    File.unlink readme_inc
   end
 
+
   ##
   # Selenium hides a .jar file using a .txt extension.