params_lookup.rb

#
# params_lookup.rb
#
# This function lookups for a variable value in various locations
# following this order
# - Hiera backend, if present
# - ::varname (if second argument is 'global')
# - ::modulename_varname
# - ::modulename::params::varname
#
# It's based on a suggestion of Dan Bode on how to better manage
# Example42 NextGen modules params lookups.
# Major help has been given by  Brice Figureau, Peter Meier
# and Ohad Levy during the Fosdem 2012 days (thanks guys)
# 
# Tested ad adapted to Puppet 2.6.x and later
#
# Alessandro Franceschi al@lab42.it
# 
module Puppet::Parser::Functions
  newfunction(:params_lookup, :type => :rvalue, :doc => <<-EOS
This fuction looks for the given variable name in a set of different sources:
- Hiera, if available (if second argument is 'global')
- Hiera, if available ('modulename_varname')
- ::varname (if second argument is 'global')
- ::modulename_varname
- ::modulename::params::varname
If no value is found in the defined sources, it returns an empty string ('')
    EOS
  ) do |arguments|

    raise(Puppet::ParseError, "params_lookup(): Define at least the variable name " +
      "given (#{arguments.size} for 1)") if arguments.size < 1

    value = ''
    var_name = arguments[0]
    module_name = parent_module_name
    
    if Puppet::Parser::Functions.function('hiera')
      value = function_hiera("#{var_name}",'') if arguments[1] == 'global'
      value = function_hiera("#{module_name}_#{var_name}",'') if ( function_hiera("#{module_name}_#{var_name}",'') != :undefined && function_hiera("#{module_name}_#{var_name}",'') != '' ) 
    end

    if value == ''
      value = lookupvar("::#{var_name}") if arguments[1] == 'global'
      value = lookupvar("::#{module_name}_#{var_name}") if ( lookupvar("::#{module_name}_#{var_name}") != :undefined && lookupvar("::#{module_name}_#{var_name}") != '' )
      value = lookupvar("::#{module_name}::params::#{var_name}") if (value == :undefined || value == '') 
    end

    return value
  end
end

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