Puppet Function: deep_merge

Defined in:
puppet/modules/stdlib/lib/puppet/parser/functions/deep_merge.rb
Function type:
Ruby 3.x API

Overview

deep_merge()Any

Recursively merges two or more hashes together and returns the resulting hash.

For example:

$hash1 = {'one' => 1, 'two' => 2, 'three' => { 'four' => 4 } }
$hash2 = {'two' => 'dos', 'three' => { 'five' => 5 } }
$merged_hash = deep_merge($hash1, $hash2)
# The resulting hash is equivalent to:
# $merged_hash = { 'one' => 1, 'two' => 'dos', 'three' => { 'four' => 4, 'five' => 5 } }

When there is a duplicate key that is a hash, they are recursively merged. When there is a duplicate key that is not a hash, the key in the rightmost hash will “win.”

Returns:

  • (Any)


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# File 'puppet/modules/stdlib/lib/puppet/parser/functions/deep_merge.rb', line 2

newfunction(:deep_merge, :type => :rvalue, :doc => <<-'ENDHEREDOC') do |args|

  if args.length < 2
  Recursively merges two or more hashes together and returns the resulting hash.

  For example:

      $hash1 = {'one' => 1, 'two' => 2, 'three' => { 'four' => 4 } }
      $hash2 = {'two' => 'dos', 'three' => { 'five' => 5 } }
      $merged_hash = deep_merge($hash1, $hash2)
      # The resulting hash is equivalent to:
      # $merged_hash = { 'one' => 1, 'two' => 'dos', 'three' => { 'four' => 4, 'five' => 5 } }

  When there is a duplicate key that is a hash, they are recursively merged.
  When there is a duplicate key that is not a hash, the key in the rightmost hash will "win."

  ENDHEREDOC
    raise Puppet::ParseError, ("deep_merge(): wrong number of arguments (#{args.length}; must be at least 2)")
  end

  deep_merge = Proc.new do |hash1,hash2|
    hash1.merge(hash2) do |key,old_value,new_value|
      if old_value.is_a?(Hash) && new_value.is_a?(Hash)
        deep_merge.call(old_value, new_value)
      else
        new_value
      end
    end
  end

  result = Hash.new
  args.each do |arg|
    next if arg.is_a? String and arg.empty? # empty string is synonym for puppet's undef
    # If the argument was not a hash, skip it.
    unless arg.is_a?(Hash)
      raise Puppet::ParseError, "deep_merge: unexpected argument type #{arg.class}, only expects hash arguments"
    end

    result = deep_merge.call(result, arg)
  end
  return( result )
end