Add new Lint/ConstantOverwrittenInRescue cop

changelog/new_add_new_lint_constant_overwritten_in_rescue.md

@@ -0,0 +1 @@
+* [#10722](https://github.com/rubocop/rubocop/pull/10722): Add new `Lint/ConstantOverwrittenInRescue` cop. ([@ydah][])

config/default.yml

@@ -1561,6 +1561,11 @@ Lint/ConstantDefinitionInBlock:
   AllowedMethods:
     - enums
 
+Lint/ConstantOverwrittenInRescue:
+  Description: 'Checks for overwriting an exception with an exception result by use `rescue =>`.'
+  Enabled: pending
+  VersionAdded: '<<next>>'
+
 Lint/ConstantResolution:
   Description: 'Check that constants are fully qualified with `::`.'
   Enabled: false

lib/rubocop.rb

@@ -279,6 +279,7 @@
 require_relative 'rubocop/cop/lint/boolean_symbol'
 require_relative 'rubocop/cop/lint/circular_argument_reference'
 require_relative 'rubocop/cop/lint/constant_definition_in_block'
+require_relative 'rubocop/cop/lint/constant_overwritten_in_rescue'
 require_relative 'rubocop/cop/lint/constant_resolution'
 require_relative 'rubocop/cop/lint/debugger'
 require_relative 'rubocop/cop/lint/deprecated_class_methods'

lib/rubocop/cop/lint/constant_overwritten_in_rescue.rb

@@ -0,0 +1,51 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Lint
+      # Checks for overwriting an exception with an exception result by use `rescue =>`.
+      #
+      # You intended to write as `rescue StandardError`.
+      # However, you have written `rescue => StandardError`.
+      # In that case, the result of `rescue` will overwrite `StandardError`.
+      #
+      # @example
+      #
+      #   # bad
+      #   begin
+      #     something
+      #   rescue => StandardError
+      #   end
+      #
+      #   # good
+      #   begin
+      #     something
+      #   rescue StandardError
+      #   end
+      #
+      class ConstantOverwrittenInRescue < Base
+        extend AutoCorrector
+        include RangeHelp
+
+        MSG = '`%<constant>s` is overwritten by `rescue =>`.'
+
+        # @!method overwritten_constant(node)
+        def_node_matcher :overwritten_constant, <<~PATTERN
+          (resbody nil? (casgn nil? $_) nil?)
+        PATTERN
+
+        def self.autocorrect_incompatible_with
+          [Naming::RescuedExceptionsVariableName, Style::RescueStandardError]
+        end
+
+        def on_resbody(node)
+          return unless (constant = overwritten_constant(node))
+
+          add_offense(node.loc.assoc, message: format(MSG, constant: constant)) do |corrector|
+            corrector.remove(range_between(node.loc.keyword.end_pos, node.loc.assoc.end_pos))
+          end
+        end
+      end
+    end
+  end
+end

spec/rubocop/cli/autocorrect_spec.rb

@@ -2518,4 +2518,30 @@ module Foo#{trailing_whitespace}
       end
     RUBY
   end
+
+  it 'corrects `Naming/RescuedExceptionsVariableName` and `, `Style/RescueStandardError`' \
+     'and `Lint/OverwriteByRescue` offenses' do
+    source_file = Pathname('example.rb')
+    create_file(source_file, <<~RUBY)
+      begin
+        something
+      rescue => StandardError
+      end
+    RUBY
+
+    status = cli.run(
+      %w[--autocorrect-all --only] << %w[
+        Naming/RescuedExceptionsVariableName
+        Style/RescueStandardError
+        Lint/ConstantOverwrittenInRescue
+      ].join(',')
+    )
+    expect(status).to eq(0)
+    expect(source_file.read).to eq(<<~RUBY)
+      begin
+        something
+      rescue StandardError
+      end
+    RUBY
+  end
 end

spec/rubocop/cop/lint/constant_overwritten_in_rescue_spec.rb

@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::Lint::ConstantOverwrittenInRescue, :config do
+  it 'registers an offense when overriding an exception with an exception result' do
+    expect_offense(<<~RUBY)
+      begin
+        something
+      rescue => StandardError
+             ^^ `StandardError` is overwritten by `rescue =>`.
+      end
+    RUBY
+
+    expect_correction(<<~RUBY)
+      begin
+        something
+      rescue StandardError
+      end
+    RUBY
+  end
+
+  it 'does not register an offense when not overriding an exception with an exception result' do
+    expect_no_offenses(<<~RUBY)
+      begin
+        something
+      rescue StandardError
+      end
+    RUBY
+  end
+
+  it 'does not register an offense when using `=>` but correctly assigning to variables' do
+    expect_no_offenses(<<~RUBY)
+      begin
+        something
+      rescue StandardError => e
+      end
+    RUBY
+  end
+end