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Add new Style/HashExcept cop
This PR adds new `Style/HashExcept` cop. This cop checks for usages of `Hash#reject`, `Hash#select`, and `Hash#filter` methods that can be replaced with `Hash#except` method. This cop should only be enabled on Ruby version 3.0 or higher. (`Hash#except` was added in Ruby 3.0.) ```ruby # bad {foo: 1, bar: 2, baz: 3}.reject {|k, v| k == :bar } {foo: 1, bar: 2, baz: 3}.select {|k, v| k != :bar } # good {foo: 1, bar: 2, baz: 3}.except(:bar) ``` cf. https://bugs.ruby-lang.org/issues/15822
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‎changelog/new_add_new_style_hash_except_cop.md‎

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* [#9283](https://github.com/rubocop-hq/rubocop/pull/9283): Add new `Style/HashExcept` cop. ([@koic][])

‎config/default.yml‎

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VersionAdded: '0.80'
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Safe: false
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Style/HashExcept:
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Description: >-
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Checks for usages of `Hash#reject`, `Hash#select`, and `Hash#filter` methods
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that can be replaced with `Hash#except` method.
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Enabled: pending
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VersionAdded: '<<next>>'
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Style/HashLikeCase:
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Description: >-
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Checks for places where `case-when` represents a simple 1:1

‎lib/rubocop.rb‎

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require_relative 'rubocop/cop/style/guard_clause'
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require_relative 'rubocop/cop/style/hash_as_last_array_item'
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require_relative 'rubocop/cop/style/hash_each_methods'
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require_relative 'rubocop/cop/style/hash_except'
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require_relative 'rubocop/cop/style/hash_like_case'
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require_relative 'rubocop/cop/style/hash_syntax'
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require_relative 'rubocop/cop/style/hash_transform_keys'

‎lib/rubocop/cop/style/hash_except.rb‎

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# frozen_string_literal: true
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module RuboCop
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module Cop
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module Style
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# This cop checks for usages of `Hash#reject`, `Hash#select`, and `Hash#filter` methods
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# that can be replaced with `Hash#except` method.
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#
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# This cop should only be enabled on Ruby version 3.0 or higher.
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# (`Hash#except` was added in Ruby 3.0.)
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#
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# For safe detection, it is limited to commonly used string and symbol comparisons
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# when used `==`.
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# And do not check `Hash#delete_if` and `Hash#keep_if` to change receiver object.
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#
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# @example
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#
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# # bad
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# {foo: 1, bar: 2, baz: 3}.reject {|k, v| k == :bar }
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# {foo: 1, bar: 2, baz: 3}.select {|k, v| k != :bar }
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# {foo: 1, bar: 2, baz: 3}.filter {|k, v| k != :bar }
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#
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# # good
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# {foo: 1, bar: 2, baz: 3}.except(:bar)
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#
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class HashExcept < Base
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include RangeHelp
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extend TargetRubyVersion
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extend AutoCorrector
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minimum_target_ruby_version 3.0
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MSG = 'Use `%<prefer>s` instead.'
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RESTRICT_ON_SEND = %i[reject select filter].freeze
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def_node_matcher :bad_method?, <<~PATTERN
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(block
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(send _ _)
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(args
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(arg _)
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(arg _))
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(send
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_ {:== :!= :eql?} _))
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PATTERN
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def on_send(node)
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block = node.parent
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return unless bad_method?(block) && semantically_except_method?(node, block)
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except_key = except_key(block)
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return unless safe_to_register_offense?(block, except_key)
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range = offense_range(node)
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preferred_method = "except(#{except_key.source})"
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add_offense(range, message: format(MSG, prefer: preferred_method)) do |corrector|
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corrector.replace(range, preferred_method)
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end
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end
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private
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def semantically_except_method?(send, block)
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body = block.body
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case send.method_name
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when :reject
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body.method?('==') || body.method?('eql?')
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when :select, :filter
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body.method?('!=')
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else
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false
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end
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end
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def safe_to_register_offense?(block, except_key)
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return true if block.body.method?('eql?')
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except_key.sym_type? || except_key.str_type?
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end
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def except_key(node)
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key_argument = node.argument_list.first
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lhs, _method_name, rhs = *node.body
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[lhs, rhs].find { |operand| operand.source != key_argument.source }
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end
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def offense_range(node)
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range_between(node.loc.selector.begin_pos, node.parent.loc.end.end_pos)
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end
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end
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end
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end
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end

‎spec/rubocop/cop/style/hash_except_spec.rb‎

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# frozen_string_literal: true
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RSpec.describe RuboCop::Cop::Style::HashExcept, :config do
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context 'Ruby 3.0 or higher', :ruby30 do
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it 'registers and corrects an offense when using `reject` and comparing with `lvar == :sym`' do
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expect_offense(<<~RUBY)
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{foo: 1, bar: 2, baz: 3}.reject { |k, v| k == :bar }
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^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `except(:bar)` instead.
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RUBY
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expect_correction(<<~RUBY)
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{foo: 1, bar: 2, baz: 3}.except(:bar)
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RUBY
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end
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it 'registers and corrects an offense when using `reject` and comparing with `:sym == lvar`' do
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expect_offense(<<~RUBY)
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{foo: 1, bar: 2, baz: 3}.reject { |k, v| :bar == k }
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^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `except(:bar)` instead.
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RUBY
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expect_correction(<<~RUBY)
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{foo: 1, bar: 2, baz: 3}.except(:bar)
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RUBY
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end
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it 'registers and corrects an offense when using `select` and comparing with `lvar != :sym`' do
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expect_offense(<<~RUBY)
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{foo: 1, bar: 2, baz: 3}.select { |k, v| k != :bar }
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^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `except(:bar)` instead.
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RUBY
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expect_correction(<<~RUBY)
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{foo: 1, bar: 2, baz: 3}.except(:bar)
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RUBY
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end
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it 'registers and corrects an offense when using `select` and comparing with `:sym != lvar`' do
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expect_offense(<<~RUBY)
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{foo: 1, bar: 2, baz: 3}.select { |k, v| :bar != k }
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^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `except(:bar)` instead.
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RUBY
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expect_correction(<<~RUBY)
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{foo: 1, bar: 2, baz: 3}.except(:bar)
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RUBY
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end
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it "registers and corrects an offense when using `reject` and comparing with `lvar == 'str'`" do
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expect_offense(<<~RUBY)
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hash.reject { |k, v| k == 'str' }
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `except('str')` instead.
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RUBY
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expect_correction(<<~RUBY)
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hash.except('str')
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RUBY
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end
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it 'registers and corrects an offense when using `reject` and other than comparison by string and symbol using `eql?`' do
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expect_offense(<<~RUBY)
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hash.reject { |k, v| k.eql?(0.0) }
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `except(0.0)` instead.
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RUBY
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expect_correction(<<~RUBY)
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hash.except(0.0)
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RUBY
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end
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it 'registers and corrects an offense when using `filter` and comparing with `lvar != :sym`' do
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expect_offense(<<~RUBY)
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{foo: 1, bar: 2, baz: 3}.filter { |k, v| k != :bar }
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^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `except(:bar)` instead.
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RUBY
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expect_correction(<<~RUBY)
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{foo: 1, bar: 2, baz: 3}.except(:bar)
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RUBY
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end
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it 'does not register an offense when using `reject` and other than comparison by string and symbol using `==`' do
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expect_no_offenses(<<~RUBY)
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hash.reject { |k, v| k == 0.0 }
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RUBY
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end
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it 'does not register an offense when using `delete_if` and comparing with `lvar == :sym`' do
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expect_no_offenses(<<~RUBY)
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{foo: 1, bar: 2, baz: 3}.delete_if { |k, v| k == :bar }
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RUBY
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end
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it 'does not register an offense when using `keep_if` and comparing with `lvar != :sym`' do
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expect_no_offenses(<<~RUBY)
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{foo: 1, bar: 2, baz: 3}.keep_if { |k, v| k != :bar }
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RUBY
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end
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end
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context 'Ruby 2.7 or lower', :ruby27 do
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it 'does not register an offense when using `reject` and comparing with `lvar == :key`' do
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expect_no_offenses(<<~RUBY)
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{foo: 1, bar: 2, baz: 3}.reject { |k, v| k == :bar }
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RUBY
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end
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it 'does not register an offense when using `reject` and comparing with `:key == lvar`' do
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expect_no_offenses(<<~RUBY)
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{foo: 1, bar: 2, baz: 3}.reject { |k, v| :bar == k }
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RUBY
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end
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it 'does not register an offense when using `select` and comparing with `lvar != :key`' do
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expect_no_offenses(<<~RUBY)
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{foo: 1, bar: 2, baz: 3}.select { |k, v| k != :bar }
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RUBY
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end
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it 'does not register an offense when using `select` and comparing with `:key != lvar`' do
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expect_no_offenses(<<~RUBY)
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{foo: 1, bar: 2, baz: 3}.select { |k, v| :bar != k }
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RUBY
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end
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end
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it 'does not register an offense when using `reject` and comparing with `lvar != :key`' do
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expect_no_offenses(<<~RUBY)
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{foo: 1, bar: 2, baz: 3}.reject { |k, v| k != :bar }
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RUBY
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end
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it 'does not register an offense when using `reject` and comparing with `:key != lvar`' do
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expect_no_offenses(<<~RUBY)
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{foo: 1, bar: 2, baz: 3}.reject { |k, v| :bar != key }
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RUBY
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end
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it 'does not register an offense when using `select` and comparing with `lvar == :key`' do
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expect_no_offenses(<<~RUBY)
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{foo: 1, bar: 2, baz: 3}.select { |k, v| k == :bar }
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RUBY
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end
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it 'does not register an offense when using `select` and comparing with `:key == lvar`' do
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expect_no_offenses(<<~RUBY)
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{foo: 1, bar: 2, baz: 3}.select { |k, v| :bar == key }
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RUBY
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end
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it 'does not register an offense when not using key block argument`' do
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expect_no_offenses(<<~RUBY)
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{foo: 1, bar: 2, baz: 3}.reject { |k, v| do_something != :bar }
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RUBY
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end
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it 'does not register an offense when not using block`' do
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expect_no_offenses(<<~RUBY)
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{foo: 1, bar: 2, baz: 3}.reject
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RUBY
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end
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it 'does not register an offense when using `Hash#except`' do
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expect_no_offenses(<<~RUBY)
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{foo: 1, bar: 2, baz: 3}.except(:bar)
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RUBY
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end
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end

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