Merge pull request #13409 from pCosta99/issue/13395

koic · web-flow · commit 910795c33952 · 2025-02-02T20:56:44.000+09:00
[Fix #13395] False positive for `Lint/UselessAssignment` when assigning in branch and block
diff --git a/changelog/fix_false_positive_for_useless_assignment.md b/changelog/fix_false_positive_for_useless_assignment.md
@@ -0,0 +1 @@
+* [#13395](https://github.com/rubocop/rubocop/issues/13395): Fix a false positive for `Lint/UselessAssignment` when assigning in branch and block. ([@pCosta99][])
diff --git a/lib/rubocop/cop/variable_force/variable.rb b/lib/rubocop/cop/variable_force/variable.rb
@@ -6,6 +6,8 @@ class VariableForce
       # A Variable represents existence of a local variable.
       # This holds a variable declaration node and some states of the variable.
       class Variable
+        extend NodePattern::Macros
+
         VARIABLE_DECLARATION_TYPES = (VARIABLE_ASSIGNMENT_TYPES + ARGUMENT_DECLARATION_TYPES).freeze
 
         attr_reader :name, :declaration_node, :scope, :assignments, :references, :captured_by_block
@@ -31,11 +33,21 @@ def initialize(name, declaration_node, scope)
         def assign(node)
           assignment = Assignment.new(node, self)
 
-          @assignments.last&.reassigned! unless captured_by_block?
+          mark_last_as_reassigned!(assignment)
 
           @assignments << assignment
         end
 
+        def mark_last_as_reassigned!(assignment)
+          return if captured_by_block?
+          return if candidate_condition?(assignment.node.parent)
+
+          @assignments.last&.reassigned!
+        end
+
+        # @!method candidate_condition?(node)
+        def_node_matcher :candidate_condition?, '[{if case case_match when}]'
+
         def referenced?
           !@references.empty?
         end
diff --git a/spec/rubocop/cop/lint/useless_assignment_spec.rb b/spec/rubocop/cop/lint/useless_assignment_spec.rb
@@ -551,6 +551,51 @@ def some_method
     end
   end
 
+  context 'when assigning in branch' do
+    it 'accepts' do
+      expect_no_offenses(<<~RUBY)
+        def some_method
+          changed = false
+
+          if Random.rand > 1
+            changed = true
+          end
+
+          [].each do
+            changed = true
+          end
+
+          puts changed
+        end
+      RUBY
+    end
+  end
+
+  context 'when assigning in case' do
+    it 'accepts' do
+      expect_no_offenses(<<~RUBY)
+        def some_method
+          changed = false
+
+          case Random.rand
+          when 0.5
+            changed = true
+          when 1..20
+            changed = false
+          when 21..70
+            changed = true
+          end
+
+          [].each do
+            changed = true
+          end
+
+          puts changed
+        end
+      RUBY
+    end
+  end
+
   context "when a variable is reassigned in loop body but won't " \
           'be referenced either next iteration or loop condition' do
     it 'registers an offense' do

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	+* [#13395](https://github.com/rubocop/rubocop/issues/13395): Fix a false positive for `Lint/UselessAssignment` when assigning in branch and block. ([@pCosta99][])