class Jbuilder

def set!(key, value = BLANK, *args, &block)
  result = if ::Kernel.block_given?
    if !_blank?(value)
      # json.comments @post.comments { |comment| ... }
      # { "comments": [ { ... }, { ... } ] }
      _scope{ array! value, &block }
    else
      # json.comments { ... }
      # { "comments": ... }
      _merge_block(key){ yield self }
    end
  elsif args.empty?
    if ::Jbuilder === value
      # json.age 32
      # json.person another_jbuilder
      # { "age": 32, "person": { ...  }
      _format_keys(value.attributes!)
    else
      # json.age 32
      # { "age": 32 }
      _format_keys(value)
    end
  elsif _is_collection?(value)
    # json.comments @post.comments, :content, :created_at
    # { "comments": [ { "content": "hello", "created_at": "..." }, { "content": "world", "created_at": "..." } ] }
    _scope{ array! value, *args }
  else
    # json.author @post.creator, :name, :email_address
    # { "author": { "name": "David", "email_address": "david@loudthinking.com" } }
    _merge_block(key){ extract! value, *args }
  end
  _set_value key, result
end