Older Puppet versions supported a small set of data types only: Bool, String, Array, and Hash. The Puppet DSL had almost no functionality to check for consistent variable types. Consider the following scenario.
A parameterized class enables other users of your code base to change the behavior and output of the class:
class ssh (
$server = true,
){
if $server {
include ssh::server
}
}This class definition checks whether the server parameter has been set to true. However, in this example, the class was not protected from wrong data usage:
class { 'ssh':
server => 'false',
}In this class declaration, the server parameter has been given a string instead of a bool value. Since the false string is not empty, the if $server condition actually passes. This is not what the user will expect.
Within Puppet 3, it was recommended to add parameter validation using several functions from the stdlib module:
class ssh (
$server = true,
){
validate_bool($server)
if $server...