Class: Puppet::Pops::Lookup

Inherits:
Object show all
Defined in:
lib/puppet/pops/lookup.rb

Overview

This class is the backing implementation of the Puppet function ‘lookup’. See puppet/functions/lookup.rb for documentation.

Class Method Summary collapse

Class Method Details

.lookup(scope, name, value_type, default_value, has_default, override, default_values_hash, merge) ⇒ Object

Performs a lookup in the configured scopes and optionally merges the default.

This is a backing function and all parameters are assumed to have been type checked. See puppet/functions/lookup.rb for full documentation and all parameter combinations.

Parameters:

  • scope (Puppet::Parser::Scope) —

    The scope to use for the lookup

  • name (String|Array<String>) —

    The name or names to lookup

  • type (Puppet::Pops::Types::PAnyType|nil) —

    The expected type of the found value

  • default_value (Object) —

    The value to use as default when no value is found

  • has_default (Boolean) —

    Set to true if default_value is included (nil is a valid default_value)

  • override (Hash<String,Object>|nil) —

    A map to use as override. Values found here are returned immediately (no merge)

  • default_values_hash (Hash<String,Object>) —

    A map to use as the last resort (but before default)

  • merge (String|Hash<String,Object>|nil) —

    Merge strategy or hash with strategy and options

Returns:

  • (Object) —

    The found value



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# File 'lib/puppet/pops/lookup.rb', line 20

def self.lookup(scope, name, value_type, default_value, has_default, override, default_values_hash, merge)
  value_type = Puppet::Pops::Types::PDataType.new if value_type.nil?
  names = name.is_a?(Array) ? name : [name]

  # find first name that yields a non-nil result and wrap it in a two element array
  # with name and value.
  not_found = Object.new
  result_with_name = names.reduce([nil,not_found]) do |memo, key|
    value = override.include?(key) ? assert_type('override', value_type, override[key]) : not_found
    value = search_and_merge(key, scope, merge, not_found) if value.equal?(not_found)
    break [key, assert_type('found', value_type, value)] unless value.equal?(not_found)
    memo
  end

  # Use the 'default_values_hash' map as a last resort if nothing is found
  if result_with_name[1].equal?(not_found) && !default_values_hash.empty?
    result_with_name = names.reduce(result_with_name) do |memo, key|
      value = default_values_hash.include?(key) ? assert_type('default_values_hash', value_type, default_values_hash[key]) : not_found
      memo = [ key, value ]
      break memo unless value.equal?(not_found)
      memo
    end
  end

  answer = result_with_name[1]
  if answer.equal?(not_found)
    if block_given?
      answer = assert_type('default_block', value_type, yield(name))
    elsif has_default
      answer = assert_type('default_value', value_type, default_value)
    else
      fail_lookup(names)
    end
  end
  answer
end