Add new Lint/DuplicateBranch cop

changelog/new_duplicate_branch_cop.md

@@ -0,0 +1 @@
+* [#8404](https://github.com/rubocop-hq/rubocop/pull/8404): Add new `Lint/DuplicateBranch` cop. ([@fatkodima][])

config/default.yml

@@ -1449,6 +1449,11 @@ Lint/DisjunctiveAssignmentInConstructor:
   VersionAdded: '0.62'
   VersionChanged: '0.88'
 
+Lint/DuplicateBranch:
+  Description: Checks that there are no repeated bodies within `if/unless`, `case-when` and `rescue` constructs.
+  Enabled: pending
+  VersionAdded: '1.3'
+
 Lint/DuplicateCaseCondition:
   Description: 'Do not repeat values in case conditionals.'
   Enabled: true

docs/modules/ROOT/pages/cops.adoc

@@ -196,6 +196,7 @@ In the following section you find all available cops:
 * xref:cops_lint.adoc#lintdeprecatedclassmethods[Lint/DeprecatedClassMethods]
 * xref:cops_lint.adoc#lintdeprecatedopensslconstant[Lint/DeprecatedOpenSSLConstant]
 * xref:cops_lint.adoc#lintdisjunctiveassignmentinconstructor[Lint/DisjunctiveAssignmentInConstructor]
+* xref:cops_lint.adoc#lintduplicatebranch[Lint/DuplicateBranch]
 * xref:cops_lint.adoc#lintduplicatecasecondition[Lint/DuplicateCaseCondition]
 * xref:cops_lint.adoc#lintduplicateelsifcondition[Lint/DuplicateElsifCondition]
 * xref:cops_lint.adoc#lintduplicatehashkey[Lint/DuplicateHashKey]

docs/modules/ROOT/pages/cops_lint.adoc

@@ -692,6 +692,75 @@ def initialize
 end
 ----
 
+== Lint/DuplicateBranch
+
+|===
+| Enabled by default | Safe | Supports autocorrection | VersionAdded | VersionChanged
+
+| Pending
+| Yes
+| No
+| 1.3
+| -
+|===
+
+This cop checks that there are no repeated bodies
+within `if/unless`, `case-when` and `rescue` constructs.
+
+=== Examples
+
+[source,ruby]
+----
+# bad
+if foo
+  do_foo
+  do_something_else
+elsif bar
+  do_foo
+  do_something_else
+end
+
+# good
+if foo || bar
+  do_foo
+  do_something_else
+end
+
+# bad
+case x
+when foo
+  do_foo
+when bar
+  do_foo
+else
+  do_something_else
+end
+
+# good
+case x
+when foo, bar
+  do_foo
+else
+  do_something_else
+end
+
+# bad
+begin
+  do_something
+rescue FooError
+  handle_error
+rescue BarError
+  handle_error
+end
+
+# good
+begin
+  do_something
+rescue FooError, BarError
+  handle_error
+end
+----
+
 == Lint/DuplicateCaseCondition
 
 |===

lib/rubocop.rb

@@ -259,6 +259,7 @@
 require_relative 'rubocop/cop/lint/deprecated_class_methods'
 require_relative 'rubocop/cop/lint/deprecated_open_ssl_constant'
 require_relative 'rubocop/cop/lint/disjunctive_assignment_in_constructor'
+require_relative 'rubocop/cop/lint/duplicate_branch'
 require_relative 'rubocop/cop/lint/duplicate_case_condition'
 require_relative 'rubocop/cop/lint/duplicate_elsif_condition'
 require_relative 'rubocop/cop/lint/duplicate_hash_key'

lib/rubocop/cop/layout/block_alignment.rb

@@ -210,10 +210,9 @@ def loc_to_source_line_column(loc)
         end
 
         def alt_start_msg(start_loc, source_line_column)
-          if style != :either
-            ''
-          elsif start_loc.line == source_line_column[:line] &&
-                start_loc.column == source_line_column[:column]
+          if style != :either ||
+             (start_loc.line == source_line_column[:line] &&
+                 start_loc.column == source_line_column[:column])
             ''
           else
             " or #{format_source_line_column(source_line_column)}"

lib/rubocop/cop/lint/duplicate_branch.rb

@@ -0,0 +1,93 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Lint
+      # This cop checks that there are no repeated bodies
+      # within `if/unless`, `case-when` and `rescue` constructs.
+      #
+      # @example
+      #   # bad
+      #   if foo
+      #     do_foo
+      #     do_something_else
+      #   elsif bar
+      #     do_foo
+      #     do_something_else
+      #   end
+      #
+      #   # good
+      #   if foo || bar
+      #     do_foo
+      #     do_something_else
+      #   end
+      #
+      #   # bad
+      #   case x
+      #   when foo
+      #     do_foo
+      #   when bar
+      #     do_foo
+      #   else
+      #     do_something_else
+      #   end
+      #
+      #   # good
+      #   case x
+      #   when foo, bar
+      #     do_foo
+      #   else
+      #     do_something_else
+      #   end
+      #
+      #   # bad
+      #   begin
+      #     do_something
+      #   rescue FooError
+      #     handle_error
+      #   rescue BarError
+      #     handle_error
+      #   end
+      #
+      #   # good
+      #   begin
+      #     do_something
+      #   rescue FooError, BarError
+      #     handle_error
+      #   end
+      #
+      class DuplicateBranch < Base
+        include RescueNode
+
+        MSG = 'Duplicate branch body detected.'
+
+        def on_branching_statement(node)
+          branches = node.branches.compact
+          branches.each_with_object(Set.new) do |branch, previous|
+            add_offense(offense_range(branch)) unless previous.add?(branch)
+          end
+        end
+        alias on_if on_branching_statement
+        alias on_case on_branching_statement
+        alias on_rescue on_branching_statement
+
+        private
+
+        def offense_range(duplicate_branch)
+          parent = duplicate_branch.parent
+
+          if parent.respond_to?(:else_branch) &&
+             parent.else_branch.equal?(duplicate_branch)
+            if parent.if_type? && parent.ternary?
+              duplicate_branch.source_range
+            else
+              parent.loc.else
+            end
+          else
+            parent.source_range
+          end
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/lint/shadowed_exception.rb

@@ -140,11 +140,10 @@ def sorted?(rescued_groups)
           rescued_groups.each_cons(2).all? do |x, y|
             if x.include?(Exception)
               false
-            elsif y.include?(Exception)
-              true
-            elsif x.none? || y.none?
-              # consider sorted if a group is empty or only contains
-              # `nil`s
+            elsif y.include?(Exception) ||
+                  # consider sorted if a group is empty or only contains
+                  # `nil`s
+                  x.none? || y.none?
               true
             else
               (x <=> y || 0) <= 0

lib/rubocop/cop/lint/useless_method_definition.rb

@@ -54,11 +54,9 @@ def optional_args?(node)
         end
 
         def delegating?(node, def_node)
-          if node.nil?
-            false
-          elsif node.zsuper_type?
+          if node&.zsuper_type?
             true
-          elsif node.super_type?
+          elsif node&.super_type?
             node.arguments.map(&:source) == def_node.arguments.map(&:source)
           else
             false

lib/rubocop/cop/style/and_or.rb

@@ -66,9 +66,7 @@ def process_logical_operator(node)
             node.each_child_node do |expr|
               if expr.send_type?
                 correct_send(expr, corrector)
-              elsif expr.return_type?
-                correct_other(expr, corrector)
-              elsif expr.assignment?
+              elsif expr.return_type? || expr.assignment?
                 correct_other(expr, corrector)
               end
             end

rubocop.gemspec

@@ -38,7 +38,7 @@ Gem::Specification.new do |s|
   s.add_runtime_dependency('rainbow', '>= 2.2.2', '< 4.0')
   s.add_runtime_dependency('regexp_parser', '>= 1.8')
   s.add_runtime_dependency('rexml')
-  s.add_runtime_dependency('rubocop-ast', '>= 1.0.1')
+  s.add_runtime_dependency('rubocop-ast', '>= 1.1.1')
   s.add_runtime_dependency('ruby-progressbar', '~> 1.7')
   s.add_runtime_dependency('unicode-display_width', '>= 1.4.0', '< 2.0')