[Fix #10864] Fix a false positive for Style/SymbolProc

changelog/fix_a_false_positive_for_style_symbol_proc_when_using_hash_reject.md

@@ -0,0 +1 @@
+* [#10864](https://github.com/rubocop/rubocop/issues/10864): Fix a false positive for `Style/SymbolProc` when using `Hash#reject`. ([@koic][])

lib/rubocop/cop/style/symbol_proc.rb

@@ -113,13 +113,14 @@ def self.autocorrect_incompatible_with
           [Layout::SpaceBeforeBlockBraces]
         end
 
-        # rubocop:disable Metrics/CyclomaticComplexity, Metrics/PerceivedComplexity
+        # rubocop:disable Metrics/AbcSize, Metrics/CyclomaticComplexity, Metrics/PerceivedComplexity
         def on_block(node)
           symbol_proc?(node) do |dispatch_node, arguments_node, method_name|
             # TODO: Rails-specific handling that we should probably make
             # configurable - https://github.com/rubocop/rubocop/issues/1485
             # we should allow lambdas & procs
             return if proc_node?(dispatch_node)
+            return if unsafe_hash_usage?(dispatch_node)
             return if %i[lambda proc].include?(dispatch_node.method_name)
             return if allowed_method_name?(dispatch_node.method_name)
             return if allow_if_method_has_argument?(node.send_node)
@@ -129,7 +130,7 @@ def on_block(node)
             register_offense(node, method_name, dispatch_node.method_name)
           end
         end
-        # rubocop:enable Metrics/CyclomaticComplexity, Metrics/PerceivedComplexity
+        # rubocop:enable Metrics/AbcSize, Metrics/CyclomaticComplexity, Metrics/PerceivedComplexity
         alias on_numblock on_block
 
         def destructuring_block_argument?(argument_node)
@@ -138,6 +139,11 @@ def destructuring_block_argument?(argument_node)
 
         private
 
+        # See: https://github.com/rubocop/rubocop/issues/10864
+        def unsafe_hash_usage?(node)
+          node.receiver&.hash_type? && %i[reject select].include?(node.method_name)
+        end
+
         def allowed_method_name?(name)
           allowed_method?(name) || matches_allowed_pattern?(name)
         end

spec/rubocop/cop/style/symbol_proc_spec.rb

@@ -150,6 +150,36 @@
     expect(&run).not_to raise_error
   end
 
+  %w[reject select].each do |method|
+    it "registers an offense when receiver is an array literal and using `#{method}` with a block" do
+      expect_offense(<<~RUBY, method: method)
+        [1, 2, 3].%{method} {|item| item.foo }
+                  _{method} ^^^^^^^^^^^^^^^^^^ Pass `&:foo` as an argument to `#{method}` instead of a block.
+      RUBY
+
+      expect_correction(<<~RUBY)
+        [1, 2, 3].#{method}(&:foo)
+      RUBY
+    end
+
+    it "registers an offense when receiver is some value and using `#{method}` with a block" do
+      expect_offense(<<~RUBY, method: method)
+        [1, 2, 3].#{method} {|item| item.foo }
+                  _{method} ^^^^^^^^^^^^^^^^^^ Pass `&:foo` as an argument to `#{method}` instead of a block.
+      RUBY
+
+      expect_correction(<<~RUBY)
+        [1, 2, 3].#{method}(&:foo)
+      RUBY
+    end
+
+    it "does not register an offense when receiver is a hash literal and using `#{method}` with a block" do
+      expect_no_offenses(<<~RUBY, method: method)
+        {foo: 42}.#{method} {|item| item.foo }
+      RUBY
+    end
+  end
+
   context 'when `AllowMethodsWithArguments: true`' do
     let(:cop_config) { { 'AllowMethodsWithArguments' => true } }
 
@@ -290,7 +320,37 @@
   end
 
   context 'numblocks', :ruby27 do
-    it 'registers an offense for a block with a single numeric argument' do
+    %w[reject select].each do |method|
+      it "registers an offense when receiver is an array literal and using `#{method}` with a numblock" do
+        expect_offense(<<~RUBY, method: method)
+          [1, 2, 3].%{method} { _1.foo }
+                    _{method} ^^^^^^^^^^ Pass `&:foo` as an argument to `#{method}` instead of a block.
+        RUBY
+
+        expect_correction(<<~RUBY)
+          [1, 2, 3].#{method}(&:foo)
+        RUBY
+      end
+
+      it "registers an offense when receiver is some value and using `#{method}` with a numblock" do
+        expect_offense(<<~RUBY, method: method)
+          do_something.%{method} { _1.foo }
+                       _{method} ^^^^^^^^^^ Pass `&:foo` as an argument to `#{method}` instead of a block.
+        RUBY
+
+        expect_correction(<<~RUBY)
+          do_something.#{method}(&:foo)
+        RUBY
+      end
+
+      it "does not register an offense when receiver is a hash literal and using `#{method}` with a numblock" do
+        expect_no_offenses(<<~RUBY, method: method)
+          {foo: 42}.#{method} { _1.foo }
+        RUBY
+      end
+    end
+
+    it 'registers an offense for a block with a numbered parameter' do
       expect_offense(<<~RUBY)
         something { _1.foo }
                   ^^^^^^^^^^ Pass `&:foo` as an argument to `something` instead of a block.
@@ -301,27 +361,27 @@
       RUBY
     end
 
-    it 'accepts block with multiple numeric argumnets' do
+    it 'accepts block with multiple numbered parameteres' do
       expect_no_offenses('something { _1 + _2 }')
     end
 
-    it 'accepts lambda with 1 argument' do
+    it 'accepts lambda with 1 numbered parameter' do
       expect_no_offenses('-> { _1.method }')
     end
 
-    it 'accepts proc with 1 argument' do
+    it 'accepts proc with 1 numbered parameter' do
       expect_no_offenses('proc { _1.method }')
     end
 
-    it 'accepts block with only second numeric argument' do
+    it 'accepts block with only second numbered parameter' do
       expect_no_offenses('something { _2.first }')
     end
 
-    it 'accepts Proc.new with 1 argument' do
+    it 'accepts Proc.new with 1 numbered parameter' do
       expect_no_offenses('Proc.new { _1.method }')
     end
 
-    it 'accepts ::Proc.new with 1 argument' do
+    it 'accepts ::Proc.new with 1 numbered parameter' do
       expect_no_offenses('::Proc.new { _1.method }')
     end
   end