How to recursively remove all keys with empty values from (YAML) hash?

Question

I have been trying to get rid of all hash keys in my YAML file that have empty (blank) values or empty hashes as values.

This earlier post helped me to get it almost right, but the recursive one-liner leaves my YAML dump with empty hashes whenever there is sufficiently deep nesting.

I would really appreciate any help on this. Thanks!

proc = Proc.new { |k, v| (v.kind_of?(Hash) && !v.empty? ) ? (v.delete_if(&proc); nil) : v.blank? }

hash = {"x"=>{"m"=>{"n"=>{}}}, 'y' => 'content'}
hash.delete_if(&proc)

Actual output

 {"x"=>{"m"=>{}}, "y"=>"content"} 

Desired output

{"y"=>"content"}

Answer 1

class Hash
  def delete_blank
    delete_if{|k, v| v.empty? or v.instance_of?(Hash) && v.delete_blank.empty?}
  end
end

p hash.delete_blank
# => {"y"=>"content"}

Answer 2

Here's a more generic method:

class Hash
  def deep_reject(&blk)
    self.dup.deep_reject!(&blk)
  end

  def deep_reject!(&blk)
    self.each do |k, v|
      v.deep_reject!(&blk)  if v.is_a?(Hash)
      self.delete(k)  if blk.call(k, v)
    end
  end
end

{ a: 1, b: nil, c: { d: nil, e: '' } }.deep_reject! { |k, v| v.blank? }
==> { a: 1 }

Answer 3

I think this the most correct version:

h = {a: {b: {c: "",}, d:1}, e:2, f: {g: {h:''}}}
p = proc do |_, v|
  v.delete_if(&p) if v.respond_to? :delete_if
  v.nil? || v.respond_to?(:"empty?") && v.empty?
end
h.delete_if(&p)
#=> {:a=>{:d=>1}, :e=>2}