Add option to reverse the check

Meaning: Warn if there are :: in front of a class definition.

Fixes voxpupuli#17.

README.md

@@ -28,7 +28,7 @@ gem 'puppet-lint-absolute_classname-check', :require => false
 
 ### Relative class name inclusion
 
-Including a class by a relative name might lead to unexpected results [in Puppet 3](https://docs.puppet.com/puppet/3/lang_namespaces.html#relative-name-lookup-and-incorrect-name-resolution). This plugin is **not** recommended for use with Puppet code that has dropped support for Puppet 3 (EOL 20161231).
+Including a class by a relative name might lead to unexpected results [in Puppet 3](https://docs.puppet.com/puppet/3/lang_namespaces.html#relative-name-lookup-and-incorrect-name-resolution).
 
 #### What you have done
 
@@ -42,6 +42,14 @@ include foobar
 include ::foobar
 ```
 
+#### Reverse this check
+
+This check can be reversed to check for Puppet > 4.
+
+```ruby
+PuppetLint.configuration.absolute_classname_reverse = true
+```
+
 #### Disabling the check
 
 To disable this check, you can add `--no-relative_classname_inclusion-check` to your puppet-lint command line.

lib/puppet-lint/plugins/check_absolute_classname.rb

@@ -1,10 +1,19 @@
 PuppetLint.new_check(:relative_classname_inclusion) do
   def check
     tokens.each_with_index do |token, token_idx|
+      reverse = PuppetLint.configuration.absolute_classname_reverse || false
+      if reverse
+        pattern = '^(?!::)'
+        message = 'class included by absolute name (::$class)'
+      else
+        pattern = '^::'
+        message = 'class included by relative name'
+      end
       if [:NAME,:FUNCTION_NAME].include?(token.type) && ['include','contain','require'].include?(token.value)
         s = token.next_code_token
         next if s.nil?
         next if s.type == :FARROW
+
         in_function = 0
         while s.type != :NEWLINE
           n = s.next_code_token
@@ -13,12 +22,12 @@ def check
               in_function += 1
             elsif in_function > 0 && n && n.type == :RPAREN
               in_function -= 1
-            elsif in_function == 0 && s.value !~ /^::/
+            elsif in_function.zero? && s.value !~ /#{pattern}/
               notify :warning, {
-                :message => 'class included by relative name',
-                :line    => s.line,
-                :column  => s.column,
-                :token   => s,
+                message: message,
+                line: s.line,
+                column: s.column,
+                token: s
               }
             end
           end
@@ -27,21 +36,26 @@ def check
       elsif token.type == :CLASS and token.next_code_token.type == :LBRACE
         s = token.next_code_token
         while s.type != :COLON
-          if (s.type == :NAME || s.type == :SSTRING) && s.value !~ /^::/
+          if (s.type == :NAME || s.type == :SSTRING) && s.value !~ /#{pattern}/
             notify :warning, {
-              :message => 'class included by relative name',
-              :line    => s.line,
-              :column  => s.column,
-              :token   => s,
+              message: message,
+              line: s.line,
+              column: s.column,
+              token: s
             }
           end
           s = s.next_token
         end
       end
     end
-  end 
+  end
 
   def fix(problem)
-    problem[:token].value = '::'+problem[:token].value
+    reverse = PuppetLint.configuration.absolute_classname_reverse || false
+    problem[:token].value = if reverse
+                              problem[:token].value[2..-1]
+                            else
+                              '::' + problem[:token].value
+                            end
   end
 end