avoid infinite loop by removing comments when receiving extended regexp

Fixes #60

Author: namusyaka

mustermann/lib/mustermann/regular.rb

@@ -21,6 +21,7 @@ class Regular < RegexpBased
     # @see (see Mustermann::Pattern#initialize)
     def initialize(string, check_anchors: true, **options)
       string = $1 if string.to_s =~ /\A\(\?\-mix\:(.*)\)\Z/ && string.inspect == "/#$1/"
+      string = string.inspect.gsub!(/(?<!\\)(?:\s|#.*(?:$|\/[mix]))/, '') if extended_regexp?(string)
       @check_anchors = check_anchors
       super(string, **options)
     end
@@ -40,6 +41,10 @@ def check_anchors(scanner)
       raise CompileError, "regular expression should not contain %s: %p" % [illegal.to_s, @string]
     end
 
-    private :compile, :check_anchors
+    def extended_regexp?(string)
+      not (Regexp.new(string).options & Regexp::EXTENDED).zero?
+    end
+
+    private :compile, :check_anchors, :extended_regexp?
   end
 end

mustermann/spec/regular_spec.rb

@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 require 'support'
+require 'timeout'
 require 'mustermann/regular'
 
 describe Mustermann::Regular do
@@ -38,6 +39,21 @@
     it { should match('/foo%2Fbar') .capturing foo: 'foo%2Fbar' }
   end
 
+
+  context 'with Regexp::EXTENDED' do
+    let(:pattern) {
+      %r{
+        \/compare\/ # match any URL beginning with \/compare\/
+        (.+)      # extract the full path (including any directories)
+        \/         # match the final slash
+        ([^.]+)   # match the first SHA1
+        \.{2,3}   # match .. or ...
+        (.+)      # match the second SHA1
+      }x
+    }
+    example { expect { Timeout.timeout(1){ Mustermann::Regular.new(pattern) }}.not_to raise_error(Timeout::Error) }
+  end
+
   describe :check_achnors do
     context 'raises on anchors' do
       example { expect { Mustermann::Regular.new('^foo')        }.to     raise_error(Mustermann::CompileError) }