module Chef::Mixin::DeepMerge
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”
@api private
Public Instance Methods
@api private
# 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
! 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)
@api private
# 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
@api private
# 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
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.
@api private
# 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
@api private
# 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
@api private
# File lib/chef/mixin/deep_merge.rb, line 111 def safe_dup(thing) thing.dup rescue TypeError thing end