test.pp

include postgresql::server
# fails because you can't override from outside a class
Fail['/var/lib/postgresql9.5/datadir'] {
  mode => '0755',
}

# succeeds because inheritance lets you override, but inheritance is spaghetti code
class test inherits postgresql::server::initdb {
  File['/var/lib/postgresql9.5/datadir'] {
    mode => '0755',
  }
}

# works because collectors can directly modify resource declarations; super hacky but less spaghetti
File <| title == '/var/lib/postgresql9.5/datadir' |> {
  mode => '0755',
}