Added new Lint/TopLevelReturnWithArgument cop (#8377)

Added new cop for detecting top-level return with argument

CHANGELOG.md

@@ -9,6 +9,7 @@
 * [#8376](https://github.com/rubocop-hq/rubocop/pull/8376): Add new `Lint/MissingSuper` cop. ([@fatkodima][])
 * [#8339](https://github.com/rubocop-hq/rubocop/pull/8339): Add `Config#for_badge` as an efficient way to get a cop's config merged with its department's. ([@marcandre][])
 * [#5067](https://github.com/rubocop-hq/rubocop/issues/5067): Add new `Style/StringConcatenation` cop. ([@fatkodima][])
+* [#7425](https://github.com/rubocop-hq/rubocop/pull/7425): Add new `Lint/TopLevelReturnWithArgument` cop. ([@iamravitejag][])
 
 ### Bug fixes
 
@@ -4717,3 +4718,4 @@
 [@CamilleDrapier]: https://github.com/CamilleDrapier
 [@shekhar-patil]: https://github.com/shekhar-patil
 [@knejad]: https://github.com/knejad
+[@iamravitejag]: https://github.com/iamravitejag

config/default.yml

@@ -1820,6 +1820,11 @@ Lint/ToJSON:
   Enabled: true
   VersionAdded: '0.66'
 
+Lint/TopLevelReturnWithArgument:
+  Description: 'This cop detects top level return statements with argument.'
+  Enabled: 'pending'
+  VersionAdded: '0.89'
+
 Lint/UnderscorePrefixedVariableName:
   Description: 'Do not use prefix `_` for a variable that is used.'
   Enabled: true

docs/modules/ROOT/pages/cops.adoc

@@ -256,6 +256,7 @@ In the following section you find all available cops:
 * xref:cops_lint.adoc#lintsuppressedexception[Lint/SuppressedException]
 * xref:cops_lint.adoc#lintsyntax[Lint/Syntax]
 * xref:cops_lint.adoc#linttojson[Lint/ToJSON]
+* xref:cops_lint.adoc#linttoplevelreturnwithargument[Lint/TopLevelReturnWithArgument]
 * xref:cops_lint.adoc#lintunderscoreprefixedvariablename[Lint/UnderscorePrefixedVariableName]
 * xref:cops_lint.adoc#lintunifiedinteger[Lint/UnifiedInteger]
 * xref:cops_lint.adoc#lintunreachablecode[Lint/UnreachableCode]

docs/modules/ROOT/pages/cops_lint.adoc

@@ -3462,6 +3462,30 @@ def to_json(*_args)
 end
 ----
 
+== Lint/TopLevelReturnWithArgument
+
+|===
+| Enabled by default | Safe | Supports autocorrection | VersionAdded | VersionChanged
+
+| Pending
+| Yes
+| No
+| 0.89
+| -
+|===
+
+This cop checks for top level return with arguments. If there is a
+top-level return statement with an argument, then the argument is
+always ignored. This is detected automatically since Ruby 2.7.
+
+=== Examples
+
+[source,ruby]
+----
+# Detected since Ruby 2.7
+return 1 # 1 is always ignored.
+----
+
 == Lint/UnderscorePrefixedVariableName
 
 |===

lib/rubocop.rb

@@ -313,6 +313,7 @@
 require_relative 'rubocop/cop/lint/suppressed_exception'
 require_relative 'rubocop/cop/lint/syntax'
 require_relative 'rubocop/cop/lint/to_json'
+require_relative 'rubocop/cop/lint/top_level_return_with_argument'
 require_relative 'rubocop/cop/lint/underscore_prefixed_variable_name'
 require_relative 'rubocop/cop/lint/unified_integer'
 require_relative 'rubocop/cop/lint/unreachable_code'

lib/rubocop/cop/lint/top_level_return_with_argument.rb

@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Lint
+      # This cop checks for top level return with arguments. If there is a
+      # top-level return statement with an argument, then the argument is
+      # always ignored. This is detected automatically since Ruby 2.7.
+      #
+      # @example
+      #
+      #   # Detected since Ruby 2.7
+      #   return 1 # 1 is always ignored.
+      class TopLevelReturnWithArgument < Cop
+        # This cop works by validating the ancestors of the return node. A
+        # top-level return node's ancestors should not be of block, def, or
+        # defs type.
+
+        MSG = 'Top level return with argument detected.'
+
+        def on_return(return_node)
+          add_offense(return_node) if return_node.arguments? && ancestors_valid?(return_node)
+        end
+
+        private
+
+        def ancestors_valid?(return_node)
+          prohibited_ancestors = return_node.each_ancestor(:block, :def, :defs)
+          prohibited_ancestors.none?
+        end
+      end
+    end
+  end
+end

spec/rubocop/cop/lint/top_level_return_with_argument_spec.rb

@@ -0,0 +1,127 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::Lint::TopLevelReturnWithArgument, :config do
+  context 'Code segment with only top-level return statement' do
+    it 'Expects no offense from the return without arguments' do
+      expect_no_offenses(<<~RUBY)
+        return
+      RUBY
+    end
+
+    it 'Expects offense from the return with arguments' do
+      expect_offense(<<~RUBY)
+        return 1, 2, 3
+        ^^^^^^^^^^^^^^ Top level return with argument detected.
+      RUBY
+    end
+
+    it 'Expects multiple offenses from the return with arguments statements' do
+      expect_offense(<<~RUBY)
+        return 1, 2, 3
+        ^^^^^^^^^^^^^^ Top level return with argument detected.
+
+        return 1, 2, 3
+        ^^^^^^^^^^^^^^ Top level return with argument detected.
+
+        return 1, 2, 3
+        ^^^^^^^^^^^^^^ Top level return with argument detected.
+      RUBY
+    end
+  end
+
+  context 'Code segment with block level returns other than the top-level return' do
+    it 'Expects no offense from the return without arguments' do
+      expect_no_offenses(<<~RUBY)
+        foo
+
+        [1, 2, 3, 4, 5].each { |n| return n }
+
+        return
+
+        bar
+      RUBY
+    end
+
+    it 'Expects offense from the return with arguments' do
+      expect_offense(<<~RUBY)
+        foo
+
+        [1, 2, 3, 4, 5].each { |n| return n }
+
+        return 1, 2, 3
+        ^^^^^^^^^^^^^^ Top level return with argument detected.
+
+        bar
+      RUBY
+    end
+  end
+
+  context 'Code segment with method-level return statements' do
+    it 'Expects offense when method-level & top-level return co-exist' do
+      expect_offense(<<~RUBY)
+        def method
+          return 'Hello World'
+        end
+
+        return 1, 2, 3
+        ^^^^^^^^^^^^^^ Top level return with argument detected.
+      RUBY
+    end
+  end
+
+  context 'Code segment with inline if along with top-level return' do
+    it 'Expects no offense from the return without arguments' do
+      expect_no_offenses(<<~RUBY)
+        foo
+
+        return if 1 == 1
+
+        bar
+
+        def method
+          return "Hello World" if 1 == 1
+        end
+      RUBY
+    end
+
+    it 'Expects multiple offense from the return with arguments' do
+      expect_offense(<<~RUBY)
+        foo
+        return 1, 2, 3 if 1 == 1
+        ^^^^^^^^^^^^^^ Top level return with argument detected.
+        bar
+        return 2
+        ^^^^^^^^ Top level return with argument detected.
+        return 3
+        ^^^^^^^^ Top level return with argument detected.
+
+        def method
+          return "Hello World" if 1 == 1
+        end
+      RUBY
+    end
+  end
+
+  context 'Code segment containing semi-colon separated statements' do
+    it 'Expects an offense from the return with arguments and multi-line code' do
+      expect_offense(<<~RUBY)
+        foo
+
+        if a == b; warn 'hey'; return 42; end
+                               ^^^^^^^^^ Top level return with argument detected.
+
+        bar
+      RUBY
+    end
+
+    it 'Expects no offense from the return with arguments and multi-line code' do
+      expect_no_offenses(<<~RUBY)
+        foo
+
+        if a == b; warn 'hey'; return; end
+
+        bar
+      RUBY
+    end
+  end
+end