Puppet

It appears that there is no consensus on how package providers should deal with an attempt to query an absent package.

At present:

*  *bsd
  propogate error or return nil

* appdmg, apple, pkgdmg no tool call (direct file system check), so not directly analogous
  return nil

* blastwave:
  Puppet.warning "Cannot match %s" % line
  return {:ensure => :absent}

* darwin port:
  raise Puppet::DevError,"Failed to match dpkg line %s" % line

* dpkg:
  return {:ensure => :purged, :status => 'missing', :name => @resource[:name], :error => 'ok'}

* gem
  Puppet.warning "Could not match %s" % desc
  return nil

* hpux
  return {:ensure => :absent}

* portage:
  raise Puppet::Error.new("No package found with the specified name [#{not_found_value}]")

* ports, rpm, rug, up2date, urpmi, yum
  return nil

The most popular answer is to return nil (which could manifest an analog of #2940); the second most popular is raising/propagating an error (which is #2999). I think my favorite would be {:ensure => :absent} but I’m unclear why this isn’t being done more often.