Module: Chef::Mixin::DeepMerge Private

Extended by:
DeepMerge
Included in:
DeepMerge
Defined in:
lib/chef/mixin/deep_merge.rb

Overview

This module is part of a private API. You should avoid using this module if possible, as it may be removed or be changed in the future.

Implements a deep merging algorithm for nested data structures.

This code was originally imported from deep_merge by Steve Midgley. deep_merge is available under the MIT license from trac.misuse.org/science/wiki/DeepMerge

Note that this is not considered a public interface. It is technically public and has been used and we cannot break the API, but continued external use is discouraged. We are unlikely to change the shape of the API and break anyone, but this code does not serve the purposes of cookbook authors and customers. It is intended only for the purposes of the internal use in the chef-client codebase. We do not accept pull requests to extend the functionality of this algorithm. Users who find this does nearly what they want, should copy and paste the algorithm and tune to their needs. We will not maintain any additional use cases.

“It is what it is, and if it isn't what you want, you need to build that yourself”

Defined Under Namespace

Classes: InvalidParameter

Instance Method Summary collapse

Instance Method Details

#deep_merge(source, dest) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.


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# File 'lib/chef/mixin/deep_merge.rb', line 151

def deep_merge(source, dest)
  deep_merge!(safe_dup(source), safe_dup(dest))
end

#deep_merge!(source, dest) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

deep_merge! method permits merging of arbitrary child elements. The two top level elements must be hashes. These hashes can contain unlimited (to stack limit) levels of child elements. These child elements to not have to be of the same types. Where child elements are of the same type, deep_merge will attempt to merge them together. Where child elements are not of the same type, deep_merge will skip or optionally overwrite the destination element with the contents of the source element at that level.

So if you have two hashes like this:

source = {:x => [1,2,3], :y => 2}
dest =   {:x => [4,5,'6'], :y => [7,8,9]}
dest.deep_merge!(source)
Results: {:x => [1,2,3,4,5,'6'], :y => 2}

By default, “deep_merge!” will overwrite any unmergeables and merge everything else. To avoid this, use “deep_merge” (no bang/exclamation mark)


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# File 'lib/chef/mixin/deep_merge.rb', line 77

def deep_merge!(source, dest)
  case source
  when Hash
    if dest.is_a?(Hash)
      source.each do |src_key, src_value|
        if dest.key?(src_key)
          dest[src_key] = deep_merge!(src_value, dest[src_key])
        else # dest[src_key] doesn't exist so we take whatever source has
          dest[src_key] = src_value
        end
      end
    else # dest isn't a hash, so we overwrite it completely
      dest = source
    end
  when Array
    if dest.is_a?(Array)
      dest |= source
    else
      dest = source
    end
  when String
    dest = source
  else # src_hash is not an array or hash, so we'll have to overwrite dest
    dest = source
  end
  dest
end

#hash_only_merge(merge_onto, merge_with) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.


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# File 'lib/chef/mixin/deep_merge.rb', line 106

def hash_only_merge(merge_onto, merge_with)
  hash_only_merge!(safe_dup(merge_onto), safe_dup(merge_with))
end

#hash_only_merge!(merge_onto, merge_with) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Deep merge without Array merge. `merge_onto` is the object that will “lose” in case of conflict. `merge_with` is the object whose values will replace `merge_onto`s values when there is a conflict.


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# File 'lib/chef/mixin/deep_merge.rb', line 124

def hash_only_merge!(merge_onto, merge_with)
  # If there are two Hashes, recursively merge.
  if merge_onto.is_a?(Hash) && merge_with.is_a?(Hash)
    merge_with.each do |key, merge_with_value|
      value =
        if merge_onto.key?(key)
          hash_only_merge(merge_onto[key], merge_with_value)
        else
          merge_with_value
        end

      if merge_onto.respond_to?(:public_method_that_only_deep_merge_should_use)
        # we can't call ImmutableMash#[]= because its immutable, but we need to mutate it to build it in-place
        merge_onto.public_method_that_only_deep_merge_should_use(key, value)
      else
        merge_onto[key] = value
      end
    end
    merge_onto
  # In all other cases, replace merge_onto with merge_with
  else
    merge_with
  end
end

#merge(first, second) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.


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# File 'lib/chef/mixin/deep_merge.rb', line 49

def merge(first, second)
  first  = Mash.new(first)  unless first.is_a?(Mash)
  second = Mash.new(second) unless second.is_a?(Mash)

  DeepMerge.deep_merge(second, first)
end

#safe_dup(thing) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.


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# File 'lib/chef/mixin/deep_merge.rb', line 111

def safe_dup(thing)
  thing.dup
rescue TypeError
  thing
end