lib/rubocop/cop/style/if_unless_modifier.rb
# frozen_string_literal: true
module RuboCop
module Cop
module Style
# Checks for `if` and `unless` statements that would fit on one line if
# written as modifier `if`/`unless`. The cop also checks for modifier
# `if`/`unless` lines that exceed the maximum line length.
#
# The maximum line length is configured in the `Layout/LineLength`
# cop. The tab size is configured in the `IndentationWidth` of the
# `Layout/IndentationStyle` cop.
#
# One-line pattern matching is always allowed. To ensure that there are few cases
# where the match variable is not used, and to prevent oversights. The variable `x`
# becomes undefined and raises `NameError` when the following example is changed to
# the modifier form:
#
# [source,ruby]
# ----
# if [42] in [x]
# x # `x` is undefined when using modifier form.
# end
# ----
#
# NOTE: It is allowed when `defined?` argument has an undefined value,
# because using the modifier form causes the following incompatibility:
#
# [source,ruby]
# ----
# unless defined?(undefined_foo)
# undefined_foo = 'default_value'
# end
# undefined_foo # => 'default_value'
#
# undefined_bar = 'default_value' unless defined?(undefined_bar)
# undefined_bar # => nil
# ----
#
# @example
# # bad
# if condition
# do_stuff(bar)
# end
#
# unless qux.empty?
# Foo.do_something
# end
#
# do_something_with_a_long_name(arg) if long_condition_that_prevents_code_fit_on_single_line
#
# # good
# do_stuff(bar) if condition
# Foo.do_something unless qux.empty?
#
# if long_condition_that_prevents_code_fit_on_single_line
# do_something_with_a_long_name(arg)
# end
#
# if short_condition # a long comment that makes it too long if it were just a single line
# do_something
# end
class IfUnlessModifier < Base
include StatementModifier
include LineLengthHelp
include AllowedPattern
include RangeHelp
include CommentsHelp
extend AutoCorrector
MSG_USE_MODIFIER = 'Favor modifier `%<keyword>s` usage when having a ' \
'single-line body. Another good alternative is ' \
'the usage of control flow `&&`/`||`.'
MSG_USE_NORMAL = 'Modifier form of `%<keyword>s` makes the line too long.'
def self.autocorrect_incompatible_with
[Style::SoleNestedConditional]
end
def on_if(node)
condition = node.condition
return if defined_nodes(condition).any? { |n| defined_argument_is_undefined?(node, n) } ||
pattern_matching_nodes(condition).any?
return unless (msg = message(node))
add_offense(node.loc.keyword, message: format(msg, keyword: node.keyword)) do |corrector|
next if part_of_ignored_node?(node)
autocorrect(corrector, node)
ignore_node(node)
end
end
private
def defined_nodes(condition)
if condition.defined_type?
[condition]
else
condition.each_descendant.select(&:defined_type?)
end
end
def defined_argument_is_undefined?(if_node, defined_node)
defined_argument = defined_node.first_argument
return false unless defined_argument.lvar_type? || defined_argument.send_type?
if_node.left_siblings.none? do |sibling|
sibling.respond_to?(:lvasgn_type?) && sibling.lvasgn_type? &&
sibling.name == defined_argument.node_parts[0]
end
end
def pattern_matching_nodes(condition)
if condition.match_pattern_type? || condition.match_pattern_p_type?
[condition]
else
condition.each_descendant.select do |node|
node.match_pattern_type? || node.match_pattern_p_type?
end
end
end
def message(node)
if single_line_as_modifier?(node) && !named_capture_in_condition?(node)
MSG_USE_MODIFIER
elsif too_long_due_to_modifier?(node)
MSG_USE_NORMAL
end
end
def autocorrect(corrector, node)
replacement = if node.modifier_form?
replacement_for_modifier_form(corrector, node)
else
to_modifier_form(node)
end
corrector.replace(node, replacement)
end
def replacement_for_modifier_form(corrector, node) # rubocop:disable Metrics/AbcSize
comment = comment_on_node_line(node)
if comment && too_long_due_to_comment_after_modifier?(node, comment)
remove_comment(corrector, node, comment)
return to_modifier_form_with_move_comment(node, indent(node), comment)
end
last_argument = node.if_branch.last_argument if node.if_branch.send_type?
if last_argument.respond_to?(:heredoc?) && last_argument.heredoc?
heredoc = extract_heredoc_from(last_argument)
remove_heredoc(corrector, heredoc)
return to_normal_form_with_heredoc(node, indent(node), heredoc)
end
to_normal_form(node, indent(node))
end
def too_long_due_to_modifier?(node)
node.modifier_form? && too_long_single_line?(node) &&
!another_statement_on_same_line?(node)
end
def too_long_due_to_comment_after_modifier?(node, comment)
source_length = processed_source.lines[node.first_line - 1].length
source_length >= max_line_length &&
source_length - comment.source_range.length <= max_line_length
end
def allowed_patterns
line_length_config = config.for_cop('Layout/LineLength')
line_length_config['AllowedPatterns'] || line_length_config['IgnoredPatterns'] || []
end
def too_long_single_line?(node)
return false unless max_line_length
range = node.source_range
return false unless range.single_line?
return false unless line_length_enabled_at_line?(range.first_line)
line = range.source_line
return false if line_length(line) <= max_line_length
too_long_line_based_on_config?(range, line)
end
def too_long_line_based_on_config?(range, line)
return false if matches_allowed_pattern?(line)
too_long = too_long_line_based_on_ignore_cop_directives?(range, line)
return too_long unless too_long == :undetermined
too_long_line_based_on_allow_uri?(line)
end
def too_long_line_based_on_ignore_cop_directives?(range, line)
if ignore_cop_directives? && directive_on_source_line?(range.line - 1)
return line_length_without_directive(line) > max_line_length
end
:undetermined
end
def too_long_line_based_on_allow_uri?(line)
if allow_uri?
uri_range = find_excessive_uri_range(line)
return false if uri_range && allowed_uri_position?(line, uri_range)
end
true
end
def line_length_enabled_at_line?(line)
processed_source.comment_config.cop_enabled_at_line?('Layout/LineLength', line)
end
def named_capture_in_condition?(node)
node.condition.match_with_lvasgn_type?
end
def non_eligible_node?(node)
non_simple_if_unless?(node) || node.chained? || node.nested_conditional? || super
end
def non_simple_if_unless?(node)
node.ternary? || node.elsif? || node.else?
end
def another_statement_on_same_line?(node)
line_no = node.source_range.last_line
# traverse the AST upwards until we find a 'begin' node
# we want to look at the following child and see if it is on the
# same line as this 'if' node
while node && !node.begin_type?
index = node.sibling_index
node = node.parent
end
node && (sibling = node.children[index + 1]) && sibling.source_range.first_line == line_no
end
def to_normal_form(node, indentation)
<<~RUBY.chomp
#{node.keyword} #{node.condition.source}
#{indentation} #{node.body.source}
#{indentation}end
RUBY
end
def to_normal_form_with_heredoc(node, indentation, heredoc)
heredoc_body, heredoc_end = heredoc
<<~RUBY.chomp
#{node.keyword} #{node.condition.source}
#{indentation} #{node.body.source}
#{indentation} #{heredoc_body.source.chomp}
#{indentation} #{heredoc_end.source.chomp}
#{indentation}end
RUBY
end
def to_modifier_form_with_move_comment(node, indentation, comment)
<<~RUBY.chomp
#{comment.source}
#{indentation}#{node.body.source} #{node.keyword} #{node.condition.source}
RUBY
end
def extract_heredoc_from(last_argument)
heredoc_body = last_argument.loc.heredoc_body
heredoc_end = last_argument.loc.heredoc_end
[heredoc_body, heredoc_end]
end
def remove_heredoc(corrector, heredoc)
heredoc.each do |range|
corrector.remove(range_by_whole_lines(range, include_final_newline: true))
end
end
def comment_on_node_line(node)
processed_source.comments.find { |c| same_line?(c, node) }
end
def remove_comment(corrector, _node, comment)
corrector.remove(range_with_surrounding_space(range: comment.source_range, side: :left))
end
end
end
end
end