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# frozen_string_literal: true
module RuboCop
module Cop
module Metrics
# This cop checks for methods with too many parameters.
#
# The maximum number of parameters is configurable.
# Keyword arguments can optionally be excluded from the total count,
# as they add less complexity than positional or optional parameters.
#
# @example Max: 3
# # good
# def foo(a, b, c = 1)
# end
#
# @example Max: 2
# # bad
# def foo(a, b, c = 1)
# end
#
# @example CountKeywordArgs: true (default)
# # counts keyword args towards the maximum
#
# # bad (assuming Max is 3)
# def foo(a, b, c, d: 1)
# end
#
# # good (assuming Max is 3)
# def foo(a, b, c: 1)
# end
#
# @example CountKeywordArgs: false
# # don't count keyword args towards the maximum
#
# # good (assuming Max is 3)
# def foo(a, b, c, d: 1)
# end
#
# This cop also checks for the maximum number of optional parameters.
# This can be configured using the `MaxOptionalParameters` config option.
#
# @example MaxOptionalParameters: 3 (default)
# # good
# def foo(a = 1, b = 2, c = 3)
# end
#
# @example MaxOptionalParameters: 2
# # bad
# def foo(a = 1, b = 2, c = 3)
# end
#
class ParameterLists < Base
exclude_limit 'Max'
exclude_limit 'MaxOptionalParameters'
MSG = 'Avoid parameter lists longer than %<max>d parameters. [%<count>d/%<max>d]'
OPTIONAL_PARAMETERS_MSG = 'Method has too many optional parameters. [%<count>d/%<max>d]'
NAMED_KEYWORD_TYPES = %i[kwoptarg kwarg].freeze
private_constant :NAMED_KEYWORD_TYPES
def on_def(node)
optargs = node.arguments.select(&:optarg_type?)
return if optargs.count <= max_optional_parameters
message = format(
OPTIONAL_PARAMETERS_MSG,
max: max_optional_parameters,
count: optargs.count
)
add_offense(node, message: message) { self.max_optional_parameters = optargs.count }
end
alias on_defs on_def
def on_args(node)
count = args_count(node)
return unless count > max_params
return if argument_to_lambda_or_proc?(node)
add_offense(node, message: format(MSG, max: max_params, count: args_count(node))) do
self.max = count
end
end
private
# @!method argument_to_lambda_or_proc?(node)
def_node_matcher :argument_to_lambda_or_proc?, <<~PATTERN
^lambda_or_proc?
PATTERN
def args_count(node)
if count_keyword_args?
node.children.size
else
node.children.count { |a| !NAMED_KEYWORD_TYPES.include?(a.type) }
end
end
def max_params
cop_config['Max']
end
def max_optional_parameters
cop_config['MaxOptionalParameters']
end
def count_keyword_args?
cop_config['CountKeywordArgs']
end
end
end
end
end