(MODULES-1582) Initial spike for % placeholder

This simply `gsub`'s the file path into where the % placeholder is.

lib/puppet/parser/functions/validate_cmd.rb

@@ -6,9 +6,9 @@ module Puppet::Parser::Functions
     Perform validation of a string with an external command.
     The first argument of this function should be a string to
     test, and the second argument should be a path to a test command
-    taking a file as last argument. If the command, launched against
-    a tempfile containing the passed string, returns a non-null value,
-    compilation will abort with a parse error.
+    taking a % as a placeholder for the file path (will default to the end).
+    If the command, launched against a tempfile containing the passed string,
+    returns a non-null value, compilation will abort with a parse error.
 
     If a third argument is specified, this will be the error message raised and
     seen by the user.
@@ -17,8 +17,12 @@ module Puppet::Parser::Functions
 
     Example:
 
+        # Defaults to end of path
         validate_cmd($sudoerscontent, '/usr/sbin/visudo -c -f', 'Visudo failed to validate sudoers content')
 
+        # % as file location
+        validate_cmd($haproxycontent, '/usr/sbin/haproxy -f % -c', 'Haproxy failed to validate config content')
+
     ENDHEREDOC
     if (args.length < 2) or (args.length > 3) then
       raise Puppet::ParseError, ("validate_cmd(): wrong number of arguments (#{args.length}; must be 2 or 3)")
@@ -34,10 +38,17 @@ module Puppet::Parser::Functions
     begin
       tmpfile.write(content)
       tmpfile.close
+
+      if checkscript.include?('%')
+        check_with_correct_location = checkscript.gsub(/%/,tmpfile.path)
+      else
+        check_with_correct_location = "#{checkscript} #{tmpfile.path}"
+      end
+
       if Puppet::Util::Execution.respond_to?('execute')
-        Puppet::Util::Execution.execute("#{checkscript} #{tmpfile.path}")
+        Puppet::Util::Execution.execute(check_with_correct_location)
       else
-        Puppet::Util.execute("#{checkscript} #{tmpfile.path}")
+        Puppet::Util.execute(check_with_correct_location)
       end
     rescue Puppet::ExecutionFailure => detail
       msg += "\n#{detail}"