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Style/InvertibleUnlessCondition
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* [#11410](https://github.com/rubocop/rubocop/issues/11410): Add new `Style/InvertibleUnlessCondition` cop. ([@fatkodima][]) |
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# frozen_string_literal: true | ||
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module RuboCop | ||
module Cop | ||
module Style | ||
# Checks for usages of `unless` which can be replaced by `if` with inverted condition. | ||
# Code without `unless` is easier to read, but that is subjective, so this cop | ||
# is disabled by default. | ||
# | ||
# Methods that can be inverted should be defined in `InverseMethods`. Note that | ||
# the relationship of inverse methods needs to be defined in both directions. | ||
# For example, | ||
# InverseMethods: | ||
# :!=: :== | ||
# :even?: :odd? | ||
# :odd?: :even? | ||
# | ||
# will suggest both `even?` and `odd?` to be inverted, but only `!=` (and not `==`). | ||
# | ||
# @safety | ||
# This cop is unsafe because it cannot be guaranteed that the method | ||
# and its inverse method are both defined on receiver, and also are | ||
# actually inverse of each other. | ||
# | ||
# @example | ||
# # bad (simple condition) | ||
# foo unless !bar | ||
# foo unless x != y | ||
# foo unless x >= 10 | ||
# foo unless x.even? | ||
# | ||
# # good | ||
# foo if bar | ||
# foo if x == y | ||
# foo if x < 10 | ||
# foo if x.odd? | ||
# | ||
# # bad (complex condition) | ||
# foo unless x != y || x.even? | ||
# | ||
# # good | ||
# foo if x == y && x.odd? | ||
# | ||
# # good (if) | ||
# foo if !condition | ||
# | ||
class InvertibleUnlessCondition < Base | ||
extend AutoCorrector | ||
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MSG = 'Favor `if` with inverted condition over `unless`.' | ||
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def on_if(node) | ||
return unless node.unless? | ||
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condition = node.condition | ||
return unless invertible?(condition) | ||
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add_offense(node) do |corrector| | ||
corrector.replace(node.loc.keyword, node.inverse_keyword) | ||
autocorrect(corrector, condition) | ||
end | ||
end | ||
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private | ||
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def invertible?(node) | ||
case node.type | ||
when :begin | ||
invertible?(node.children.first) | ||
when :send | ||
return if inheritance_check?(node) | ||
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node.method?(:!) || inverse_methods.key?(node.method_name) | ||
when :or, :and | ||
invertible?(node.lhs) && invertible?(node.rhs) | ||
else | ||
false | ||
end | ||
end | ||
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def inheritance_check?(node) | ||
argument = node.first_argument | ||
node.method?(:<) && | ||
(argument.const_type? && argument.short_name.to_s.upcase != argument.short_name.to_s) | ||
end | ||
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def autocorrect(corrector, node) | ||
case node.type | ||
when :begin | ||
autocorrect(corrector, node.children.first) | ||
when :send | ||
autocorrect_send_node(corrector, node) | ||
when :or, :and | ||
corrector.replace(node.loc.operator, node.inverse_operator) | ||
autocorrect(corrector, node.lhs) | ||
autocorrect(corrector, node.rhs) | ||
end | ||
end | ||
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def autocorrect_send_node(corrector, node) | ||
if node.method?(:!) | ||
corrector.remove(node.loc.selector) | ||
else | ||
corrector.replace(node.loc.selector, inverse_methods[node.method_name]) | ||
end | ||
end | ||
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def inverse_methods | ||
@inverse_methods ||= cop_config['InverseMethods'] | ||
end | ||
end | ||
end | ||
end | ||
end |
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spec/rubocop/cop/style/invertible_unless_condition_spec.rb
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# frozen_string_literal: true | ||
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RSpec.describe RuboCop::Cop::Style::InvertibleUnlessCondition, :config do | ||
let(:cop_config) do | ||
{ | ||
'InverseMethods' => { | ||
:!= => :==, | ||
:even? => :odd?, | ||
:odd? => :even?, | ||
:>= => :<, | ||
:< => :>=, | ||
:zero? => :nonzero? | ||
} | ||
} | ||
end | ||
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context 'when invertible `unless`' do | ||
it 'registers an offense and corrects when using `!` negation' do | ||
expect_offense(<<~RUBY) | ||
foo unless !x | ||
^^^^^^^^^^^^^ Favor `if` with inverted condition over `unless`. | ||
foo unless !!x | ||
^^^^^^^^^^^^^^ Favor `if` with inverted condition over `unless`. | ||
RUBY | ||
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expect_correction(<<~RUBY) | ||
foo if x | ||
foo if !x | ||
RUBY | ||
end | ||
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it 'registers an offense and corrects when using simple operator condition' do | ||
expect_offense(<<~RUBY) | ||
foo unless x != y | ||
^^^^^^^^^^^^^^^^^ Favor `if` with inverted condition over `unless`. | ||
RUBY | ||
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expect_correction(<<~RUBY) | ||
foo if x == y | ||
RUBY | ||
end | ||
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it 'registers an offense and corrects when using simple method condition' do | ||
expect_offense(<<~RUBY) | ||
foo unless x.odd? | ||
^^^^^^^^^^^^^^^^^ Favor `if` with inverted condition over `unless`. | ||
RUBY | ||
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expect_correction(<<~RUBY) | ||
foo if x.even? | ||
RUBY | ||
end | ||
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it 'registers an offense and corrects when using simple bracketed condition' do | ||
expect_offense(<<~RUBY) | ||
foo unless ((x != y)) | ||
^^^^^^^^^^^^^^^^^^^^^ Favor `if` with inverted condition over `unless`. | ||
RUBY | ||
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expect_correction(<<~RUBY) | ||
foo if ((x == y)) | ||
RUBY | ||
end | ||
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it 'registers an offense and corrects when using complex condition' do | ||
expect_offense(<<~RUBY) | ||
foo unless x != y && (((x.odd?) || (((y >= 5)))) || z.zero?) | ||
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Favor `if` with inverted condition over `unless`. | ||
RUBY | ||
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expect_correction(<<~RUBY) | ||
foo if x == y || (((x.even?) && (((y < 5)))) && z.nonzero?) | ||
RUBY | ||
end | ||
end | ||
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it 'does not register an offense when using non invertible `unless`' do | ||
expect_no_offenses(<<~RUBY) | ||
foo unless x != y || x.awesome? | ||
RUBY | ||
end | ||
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it 'does not register an offense when checking for inheritance' do | ||
expect_no_offenses(<<~RUBY) | ||
foo unless x < Foo | ||
RUBY | ||
end | ||
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it 'does not register an offense when using invertible `if`' do | ||
expect_no_offenses(<<~RUBY) | ||
foo if !condition | ||
RUBY | ||
end | ||
end |
one?
andmany?
aren't inverse methods, in case you're motivated to remove these examples (e.g. they return the same result on empty collections)