delete_nested_subkeys

gistfile1.rb

#
# delete_child_subkey.rb
#
# === Author
#
# Richard Clark <richard@fohnet.co.uk>
#
module Puppet::Parser::Functions
  newfunction(:delete_child_subkey, :type => :rvalue, :doc => <<-EOS
Given a hash containing nested hashes, a single or array of regular
expressions, and a single, or array of third-depth keys to match, this function
will delete those keys from second level hash structure, where those second
level keys match any of the given regular expressions

This is primarily intended for sharing hiera data structures between multiple
classes that require similar, but not identical data in order to pass back to a
define/defined type using create_resouces or equivilant.

Anything that is not a nested hash, or does not match the regular expression is passed to the output without processing further.

See also: insert_child_subkey(), delete()

*Examples:*

A given variable $hiera_puppet_modules which contains a hash:

hiera_puppet_modules = {
  'puppet_module_vsftpd' => {
    'ensure'   => 'present',
    'git_repo' => 'git@git.mydomain',
    'branch'   => 'production',
    'unwanted' => 'data',
  },
  'puppet_module_this' => 'that',
  'array_of_data' => [ 'some', 'things' ],
  'my_code_repo' => {
    'ensure'   => 'present',
    'git_repo' => 'git@git.mydomain',
    'branch'   => 'production',
    'spurious' => 'data',
    'unwanted' => 'data',
  },
  'puppet_module_apache' => {
    'ensure'   => 'present',
    'git_repo' => 'git@git.mydomain',
    'branch'   => 'production',
    'spurious' => 'data',
  }
}

A regular expession matching: '^puppet_module_'

And a set of subkeys matching: ['git_repo', 'branch', 'spurious', 'data' ]

Passed to this function as: delete_child_subkey(
  $hiera_puppet_modules,
  '^puppet_module_',
  ['git_repo', 'branch', 'spurious', 'data' ]
)

Would give:

hiera_puppet_modules = {
  'puppet_module_vsftpd' => {
    'ensure'   => 'present',
  },
  'puppet_module_this' => 'that',
  'array_of_data' => [ 'some', 'things' ],
  'my_code_repo' => {
    'ensure'   => 'present',
    'git_repo' => 'git@git.mydomain',
    'branch'   => 'production',
    'spurious' => 'data',
    'unwanted' => 'data',
  },
  'puppet_module_apache' => {
    'ensure'   => 'present',
  }
}

EOS
  ) do |arguments|

    if (arguments.size != 3) then
      raise(Puppet::ParseError, "delete_child_subkey(): Wrong number of arguments "+
        "given #{arguments.size} for 3.")
    end

    src_hash = arguments[0]
    regex    = arguments[1]
    del_key  = arguments[2]

    unless src_hash.is_a?(Hash)
      raise Puppet::ParseError, "First argument must be a hash"
    end
    unless regex.is_a?(String) or regex.is_a?(Array)
      raise Puppet::ParseError, "Second argument must be a single or array of string-format regex"
    end
    unless del_key.is_a?(String) or del_key.is_a?(Array)
      raise Puppet::ParseError, "Third argument must be a single or array of keys to delete at third level depth"
    end

    # transform regex + del_key into arrays if they are not already
    regex = [ regex ] if regex.is_a?(String)
    del_key = [ del_key ] if del_key.is_a?(String)
    # destination hash to store wanted data structure
    dest_hash = Hash.new
    
    # get second level keys
    src_hash.keys.each do |parent|
      # if it's not a hash, just insert it and move on
      unless src_hash[parent].is_a?(Hash)
        dest_hash[parent] = src_hash[parent]
        next
      end
      # create empty hash nested at parent in destination hash
      dest_hash[parent] = Hash.new
      src_hash[parent].keys.each do |child|
        regex.each do |r|
          if parent !~ /#{r}/
            # if we don't match the regex, insert the values and move on
            dest_hash[parent][child] = src_hash[parent][child]
            break
          else
            # otherwise we match, so insert the keys, but only if they're on in
            # the del_key list
            dest_hash[parent][child] = src_hash[parent][child] unless del_key.include?(child)
            break
          end
        end
      end
    end
    dest_hash
  end
end

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