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 http://trac.misuse.org/science/wiki/DeepMerge
Regex to match the "knockout prefix" that was used to indicate subtractive merging in Chef 10.x and previous. Subtractive merging is removed as of Chef 11, but we detect attempted use of it and raise an error (see: raise_if_knockout_used!)
# File lib/chef/mixin/deep_merge.rb, line 160 def deep_merge(source, dest) deep_merge!(source.dup, dest.dup) end
Deep Merge core documentation. 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)
# File lib/chef/mixin/deep_merge.rb, line 75 def deep_merge!(source, dest) # if dest doesn't exist, then simply copy source to it if dest.nil? dest = source; return dest end raise_if_knockout_used!(source) raise_if_knockout_used!(dest) case source when nil dest when Hash source.each do |src_key, src_value| if dest.kind_of?(Hash) if dest[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 raise_if_knockout_used!(src_value) dest[src_key] = src_value end else # dest isn't a hash, so we overwrite it completely dest = source end end when Array if dest.kind_of?(Array) dest = 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
# File lib/chef/mixin/deep_merge.rb, line 113 def hash_only_merge(merge_onto, merge_with) hash_only_merge!(merge_onto.dup, merge_with.dup) 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.
# File lib/chef/mixin/deep_merge.rb, line 121 def hash_only_merge!(merge_onto, merge_with) # If there are two Hashes, recursively merge. if merge_onto.kind_of?(Hash) && merge_with.kind_of?(Hash) merge_with.each do |key, merge_with_value| merge_onto[key] = hash_only_merge!(merge_onto[key], merge_with_value) end merge_onto # If merge_with is nil, don't replace merge_onto elsif merge_with.nil? merge_onto # In all other cases, replace merge_onto with merge_with else merge_with end end
# File lib/chef/mixin/deep_merge.rb, line 43 def merge(first, second) first = Mash.new(first) unless first.kind_of?(Mash) second = Mash.new(second) unless second.kind_of?(Mash) DeepMerge.deep_merge(second, first) end
Checks for attempted use of subtractive merge, which was removed for Chef 11.0. If subtractive merge use is detected, will raise an InvalidSubtractiveMerge exception.
# File lib/chef/mixin/deep_merge.rb, line 142 def raise_if_knockout_used!(obj) if uses_knockout?(obj) raise InvalidSubtractiveMerge, "subtractive merge with !merge is no longer supported" end end
Inherited roles use the knockout_prefix array subtraction functionality This is likely to go away in Chef >= 0.11
# File lib/chef/mixin/deep_merge.rb, line 52 def role_merge(first, second) first = Mash.new(first) unless first.kind_of?(Mash) second = Mash.new(second) unless second.kind_of?(Mash) DeepMerge.deep_merge(second, first) end
Checks for attempted use of subtractive merge in obj.
# File lib/chef/mixin/deep_merge.rb, line 149 def uses_knockout?(obj) case obj when String obj =~ OLD_KNOCKOUT_MATCH when Array obj.any? {|element| element.respond_to?(:gsub) && element =~ OLD_KNOCKOUT_MATCH } else false end end
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