Puppet inheritance of parametrized classes

[Answering own question after getting around to prodding at the config for a while]

I've managed to track this down to one of the modules which I have written (of course), but it was due to a use of a variable which didn't work out how I expected.

What happened was:

$variable_dir = "/etc/puppet/bar"

class foo {
  file { $variable_dir:
    ensure => directory
  }
}

define some-define() {
   # Trimmed for brevity
   exec { "some-$name":
     # command, creates, timeout etc here
     require => File[$variable_dir],
   }
}

..which basically caused some confusion with the File[] using a variable. I've replaced these with the explicit value of the variable for now and it all works fine, but it was something of a surprise! I'm assuming that my understanding of scope and when variables can be defined/used is somewhat out of whack with Puppet, so I'm going to learn that a lot better...

It seems to have caused the same behaviour as using non-fully-qualified paths on file strings, by failing to find the variable or not obtaining the value? Quite odd, anyway.

Edit : It's quite possible that the variable wasn't found in scope, and so was empty and definitely not a fully-qualified path. Doesn't explain why this was not consistent, however...

Two things regarding your puppet code.

The define should be in it's own file (named add_user.pp, and located in the <modulename>/manifests/ folder) , rather than in the class file.

Set the define up (change $name to $username, as $name is a reserved variable), and then add the same set of parameters as the define uses to the class. (which in your example would be $modulepath/users/manifests/add.pp to make it work with the autoloader)

If you change the class as follows:

class users::add( $u_name, $u_comment, $u_home, $u_shell, $u_uid, $u_gid, $u_password)
{
  users::add_user{ $u_name:
    $username => $u_name, 
    $comment  => $u_comment, 
    $home     => $u_home, 
    $shell    => $u_shell, 
    $uid      => $u_uid, 
    $gid      => $u_gid, 
    $password => $u_password,
  }
}

And change the site.pp to:

 import "classes/*.pp"
    node default{
      class { 'add_user': 
        username => "saga",
        comment => "Arun Sag",
        gid => "100",
        home => "/home/saga",
        password => '$1$passwordhash/',
        shell => "/bin/bash",
        uid => "70960",
      }
    }

For the yaml, something like this will do it, please refer to the documentation for more details:

---
classes:
  users::add:

parameters:
  name: some_name
  comment: some_comment
  home: home_value
  shell: /bin/sh
  uid: 3990
  gid: 3990
  password: superstrongpassword

environment:
  production