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Contents
# frozen_string_literal: true
module RuboCop
module Cop
module Style
# This cop enforces the use of `$stdout/$stderr/$stdin` instead of `STDOUT/STDERR/STDIN`.
# `STDOUT/STDERR/STDIN` are constants, and while you can actually
# reassign (possibly to redirect some stream) constants in Ruby, you'll get
# an interpreter warning if you do so.
#
# @safety
# Autocorrection is unsafe because `STDOUT` and `$stdout` may point to different
# objects, for example.
#
# @example
# # bad
# STDOUT.puts('hello')
#
# hash = { out: STDOUT, key: value }
#
# def m(out = STDOUT)
# out.puts('hello')
# end
#
# # good
# $stdout.puts('hello')
#
# hash = { out: $stdout, key: value }
#
# def m(out = $stdout)
# out.puts('hello')
# end
#
class GlobalStdStream < Base
extend AutoCorrector
MSG = 'Use `%<gvar_name>s` instead of `%<const_name>s`.'
STD_STREAMS = %i[STDIN STDOUT STDERR].to_set.freeze
# @!method const_to_gvar_assignment?(node, name)
def_node_matcher :const_to_gvar_assignment?, <<~PATTERN
(gvasgn %1 (const nil? _))
PATTERN
def on_const(node)
const_name = node.children[1]
return unless STD_STREAMS.include?(const_name)
gvar_name = gvar_name(const_name).to_sym
return if const_to_gvar_assignment?(node.parent, gvar_name)
add_offense(node, message: message(const_name)) do |corrector|
corrector.replace(node, gvar_name)
end
end
private
def message(const_name)
format(MSG, gvar_name: gvar_name(const_name), const_name: const_name)
end
def gvar_name(const_name)
"$#{const_name.to_s.downcase}"
end
end
end
end
end
Version data entries
21 entries across 21 versions & 4 rubygems