def self.make_block_optional(mod, *methods)
mod = class << mod; self; end unless mod.is_a? Module
options = methods.last.is_a?(Hash) ? methods.pop : {}
methods.each do |selector|
unless mod.method_defined? selector
warn "#{mod}##{selector} is not defined, so block can't be made optional"
next
end
unless options[:force]
test_on = options.fetch(:test_on)
result = begin
test_on.send(selector, *options.fetch(:arg, []))
rescue LocalJumpError
false
end
next if result.class.name =~ /Enumerator$/
end
require 'enumerator'
arity = mod.instance_method(selector).arity
last_arg = []
if arity < 0
last_arg = ["*rest"]
arity = -1-arity
end
arg_sequence = ((0...arity).map{|i| "arg_#{i}"} + last_arg + ["&block"]).join(", ")
alias_method_chain(mod, selector, :optional_block) do |aliased_target, punctuation|
mod.module_eval "def \#{aliased_target}_with_optional_block\#{punctuation}(\#{arg_sequence})\nreturn to_enum(:\#{aliased_target}_without_optional_block\#{punctuation}, \#{arg_sequence}) unless block_given?\n\#{aliased_target}_without_optional_block\#{punctuation}(\#{arg_sequence})\nend\n", __FILE__, __LINE__ + 1
end
end
end