Add new Lint/RequireRangeParentheses cop

changelog/new_add_new_lint_require_range_parentheses_cop.md

@@ -0,0 +1 @@
+* [#10792](https://github.com/rubocop/rubocop/pull/10792): Add new `Lint/RequireRangeParentheses` cop. ([@koic][])

config/default.yml

@@ -2128,6 +2128,11 @@ Lint/RequireParentheses:
   Enabled: true
   VersionAdded: '0.18'
 
+Lint/RequireRangeParentheses:
+  Description: 'Checks that a range literal is enclosed in parentheses when the end of the range is at a line break.'
+  Enabled: pending
+  VersionAdded: '<<next>>'
+
 Lint/RequireRelativeSelfPath:
   Description: 'Checks for uses a file requiring itself with `require_relative`.'
   Enabled: pending

lib/rubocop.rb

@@ -356,6 +356,7 @@
 require_relative 'rubocop/cop/lint/refinement_import_methods'
 require_relative 'rubocop/cop/lint/regexp_as_condition'
 require_relative 'rubocop/cop/lint/require_parentheses'
+require_relative 'rubocop/cop/lint/require_range_parentheses'
 require_relative 'rubocop/cop/lint/require_relative_self_path'
 require_relative 'rubocop/cop/lint/rescue_exception'
 require_relative 'rubocop/cop/lint/rescue_type'

lib/rubocop/cop/lint/require_range_parentheses.rb

@@ -0,0 +1,57 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Lint
+      # Checks that a range literal is enclosed in parentheses when the end of the range is
+      # at a line break.
+      #
+      # NOTE: The following is maybe intended for `(42..)`. But, compatible is `42..do_something`.
+      # So, this cop does not provide autocorrection because it is left to user.
+      #
+      # [source,ruby]
+      # ----
+      # case condition
+      # when 42..
+      #   do_something
+      # end
+      # ----
+      #
+      # @example
+      #
+      #   # bad - Represents `(1..42)`, not endless range.
+      #   1..
+      #   42
+      #
+      #   # good - It's incompatible, but your intentions when using endless range may be:
+      #   (1..)
+      #   42
+      #
+      #   # good
+      #   1..42
+      #
+      #   # good
+      #   (1..42)
+      #
+      #   # good
+      #   (1..
+      #   42)
+      #
+      class RequireRangeParentheses < Base
+        MSG = 'Wrap the endless range literal `%<range>s` to avoid precedence ambiguity.'
+
+        def on_irange(node)
+          return if node.parent&.begin_type?
+          return unless node.begin && node.end
+          return if same_line?(node.begin, node.end)
+
+          message = format(MSG, range: "#{node.begin.source}#{node.loc.operator.source}")
+
+          add_offense(node, message: message)
+        end
+
+        alias on_erange on_irange
+      end
+    end
+  end
+end

spec/rubocop/cop/lint/require_range_parentheses_spec.rb

@@ -0,0 +1,60 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::Lint::RequireRangeParentheses, :config do
+  it 'registers an offense when the end of the range (`..`) is line break' do
+    expect_offense(<<~RUBY)
+      42..
+      ^^^^ Wrap the endless range literal `42..` to avoid precedence ambiguity.
+      do_something
+    RUBY
+  end
+
+  it 'registers an offense when the end of the range (`...`) is line break' do
+    expect_offense(<<~RUBY)
+      42...
+      ^^^^^ Wrap the endless range literal `42...` to avoid precedence ambiguity.
+      do_something
+    RUBY
+  end
+
+  it 'does not register an offense when the end of the range (`..`) is line break and is enclosed in parentheses' do
+    expect_no_offenses(<<~RUBY)
+      (42..
+      do_something)
+    RUBY
+  end
+
+  context 'Ruby >= 2.6', :ruby26 do
+    it 'does not register an offense when using endless range only' do
+      expect_no_offenses(<<~RUBY)
+        42..
+      RUBY
+    end
+  end
+
+  context 'Ruby >= 2.7', :ruby27 do
+    it 'does not register an offense when using beginless range only' do
+      expect_no_offenses(<<~RUBY)
+        ..42
+      RUBY
+    end
+  end
+
+  it 'does not register an offense when using `42..nil`' do
+    expect_no_offenses(<<~RUBY)
+      42..nil
+    RUBY
+  end
+
+  it 'does not register an offense when using `nil..42`' do
+    expect_no_offenses(<<~RUBY)
+      nil..42
+    RUBY
+  end
+
+  it 'does not register an offense when begin and end of the range are on the same line' do
+    expect_no_offenses(<<~RUBY)
+      42..do_something
+    RUBY
+  end
+end