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Add new Style/ClassEqualityComparison
cop
#8833
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bbatsov
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rubocop:master
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fatkodima:class_equality_comparison-cop
Oct 8, 2020
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,49 @@ | ||
# frozen_string_literal: true | ||
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module RuboCop | ||
module Cop | ||
module Style | ||
# This cop enforces the use of `Object#instance_of?` instead of class comparison | ||
# for equality. | ||
# | ||
# @example | ||
# # bad | ||
# var.class == Date | ||
# var.class.equal?(Date) | ||
# var.class.eql?(Date) | ||
# var.class.name == 'Date' | ||
# | ||
# # good | ||
# var.instance_of?(Date) | ||
# | ||
class ClassEqualityComparison < Base | ||
include RangeHelp | ||
include IgnoredMethods | ||
extend AutoCorrector | ||
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MSG = 'Use `Object.instance_of?` instead of comparing classes.' | ||
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RESTRICT_ON_SEND = %i[== equal? eql?].freeze | ||
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def_node_matcher :class_comparison_candidate?, <<~PATTERN | ||
(send | ||
{$(send _ :class) (send $(send _ :class) :name)} | ||
{:== :equal? :eql?} $_) | ||
PATTERN | ||
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def on_send(node) | ||
def_node = node.each_ancestor(:def, :defs).first | ||
return if def_node && ignored_method?(def_node.method_name) | ||
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class_comparison_candidate?(node) do |receiver_node, class_node| | ||
range = range_between(receiver_node.loc.selector.begin_pos, node.source_range.end_pos) | ||
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add_offense(range) do |corrector| | ||
corrector.replace(range, "instance_of?(#{class_node.source})") | ||
end | ||
end | ||
end | ||
end | ||
end | ||
end | ||
end |
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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,46 @@ | ||
# frozen_string_literal: true | ||
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RSpec.describe RuboCop::Cop::Style::ClassEqualityComparison, :config do | ||
let(:cop_config) do | ||
{ 'IgnoredMethods' => [] } | ||
end | ||
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it 'registers an offense and corrects when comparing class for equality' do | ||
expect_offense(<<~RUBY) | ||
var.class == Date | ||
^^^^^^^^^^^^^ Use `Object.instance_of?` instead of comparing classes. | ||
var.class.equal?(Date) | ||
^^^^^^^^^^^^^^^^^^ Use `Object.instance_of?` instead of comparing classes. | ||
var.class.eql?(Date) | ||
^^^^^^^^^^^^^^^^ Use `Object.instance_of?` instead of comparing classes. | ||
RUBY | ||
end | ||
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it 'registers an offense and corrects when comparing class name for equality' do | ||
expect_offense(<<~RUBY) | ||
var.class.name == "Date" | ||
^^^^^^^^^^^^^^^^^^^^ Use `Object.instance_of?` instead of comparing classes. | ||
RUBY | ||
end | ||
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it 'does not register an offense when using `instance_of?`' do | ||
expect_no_offenses(<<~RUBY) | ||
var.instance_of?(Date) | ||
RUBY | ||
end | ||
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context 'when IgnoredMethods is specified' do | ||
let(:cop_config) do | ||
{ 'IgnoredMethods' => ['=='] } | ||
end | ||
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it 'does not register an offense when comparing class for equality' do | ||
expect_no_offenses(<<~RUBY) | ||
def ==(other) | ||
self.class == other.class && | ||
name == other.name | ||
end | ||
RUBY | ||
end | ||
end | ||
end |
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Btw, you can use
kind_of?
as well. I think we have some other cop for this, so that one should honor the config of the existing cop.There was a problem hiding this comment.
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kind_of?
is an alias foris_a?
, which checks also superclasses. So this should beinstance_of?
for sure.There was a problem hiding this comment.
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I keep mixing those up. :-)