[Fix rubocop#11006] Allow multiple elsif for `Style/IfWithBooleanLi…

…teralBranches`

Fixes rubocop#11006.

This PR allows multiple `elsif` for `Style/IfWithBooleanLiteralBranches`.

I think it's good to allow when multiple `elsif`s are used instead of a new config option.
OTOH, if there is only single `elsif`, `elsif` will not exist due to autocorrection.
So I think the current behavior can be kept.

changelog/change_allow_multiple_elsif_for_style_if_with_boolean_literal_branches.md

@@ -0,0 +1 @@
+* [#11006](https://github.com/rubocop/rubocop/issues/11006): Allow multiple `elsif` for `Style/IfWithBooleanLiteralBranches`. ([@koic][])

lib/rubocop/cop/style/if_with_boolean_literal_branches.rb

@@ -8,6 +8,20 @@ module Style
       # The conditions to be checked are comparison methods, predicate methods, and double negative.
       # `nonzero?` method is allowed by default.
       # These are customizable with `AllowedMethods` option.
+      # This cop targets only `if`s with a single `elsif` or `else` branch.
+      #
+      # [source,ruby]
+      # ----
+      # if foo
+      #   true
+      # elsif bar > baz
+      #   true
+      # elsif qux > quux # Single `elsif` is warned, but two or more `elsif`s are not.
+      #   true
+      # else
+      #   false
+      # end
+      # ----
       #
       # @safety
       #   Autocorrection is unsafe because there is no guarantee that all predicate methods
@@ -57,7 +71,7 @@ class IfWithBooleanLiteralBranches < Base
         def_node_matcher :double_negative?, '(send (send _ :!) :!)'
 
         def on_if(node)
-          return unless if_with_boolean_literal_branches?(node)
+          return if !if_with_boolean_literal_branches?(node) || multiple_elsif?(node)
 
           condition = node.condition
           range, keyword = offense_range_with_keyword(node, condition)
@@ -76,6 +90,12 @@ def on_if(node)
 
         private
 
+        def multiple_elsif?(node)
+          return false unless (parent = node.parent)
+
+          parent.if_type? && parent.elsif?
+        end
+
         def offense_range_with_keyword(node, condition)
           if node.ternary?
             range = condition.source_range.end.join(node.source_range.end)

spec/rubocop/cop/style/if_with_boolean_literal_branches_spec.rb

@@ -85,6 +85,25 @@
         RUBY
       end
 
+      it 'registers and corrects an offense when using `if` with boolean literal branches directly under `def`' do
+        expect_offense(<<~RUBY, comparison_operator: comparison_operator)
+          def foo
+            if bar > baz
+            ^^ Remove redundant `if` with boolean literal branches.
+              true
+            else
+              false
+            end
+          end
+        RUBY
+
+        expect_correction(<<~RUBY)
+          def foo
+            bar > baz
+          end
+        RUBY
+      end
+
       it 'does not register an offense when using a branch that is not boolean literal' do
         expect_no_offenses(<<~RUBY)
           if foo #{comparison_operator} bar
@@ -555,6 +574,43 @@
     end
   end
 
+  context 'when using `elsif` with boolean literal branches' do
+    it 'registers and corrects an offense when using single `elsif` with boolean literal branches' do
+      expect_offense(<<~RUBY)
+        if foo
+          true
+        elsif bar > baz
+        ^^^^^ Use `else` instead of redundant `elsif` with boolean literal branches.
+          true
+        else
+          false
+        end
+      RUBY
+
+      expect_correction(<<~RUBY)
+        if foo
+          true
+        else
+          bar > baz
+        end
+      RUBY
+    end
+
+    it 'does not register an offense when using multiple `elsif` with boolean literal branches' do
+      expect_no_offenses(<<~RUBY)
+        if foo
+          true
+        elsif bar > baz
+          true
+        elsif qux > quux
+          true
+        else
+          false
+        end
+      RUBY
+    end
+  end
+
   context 'when `AllowedMethods: nonzero?`' do
     let(:cop_config) { { 'AllowedMethods' => ['nonzero?'] } }