[Fix rubocop#3006] Handle merge called on a method on the receiver in…

… RedundantMerge (rubocop#3035)

CHANGELOG.md

@@ -17,7 +17,7 @@
 * [#2314](https://github.com/bbatsov/rubocop/pull/2314): Ignore `UnusedBlockArgument` for keyword arguments. ([@volkert][])
 * [#2975](https://github.com/bbatsov/rubocop/issues/2975): Make comment indentation before `)` consistent with comment indentation before `}` or `]`. ([@jonas054][])
 * [#3010](https://github.com/bbatsov/rubocop/issues/3010): Fix double reporting/correction of spaces after ternary operator colons (now only reported by `Style/SpaceAroundOperators`, and not `Style/SpaceAfterColon` too). ([@owst][])
-* [#3006](https://github.com/bbatsov/rubocop/issues/3006): Handle non-local variables as receivers inside `each_with_object` in `Performance/RedundantMerge`. ([@lumeet][])
+* [#3006](https://github.com/bbatsov/rubocop/issues/3006): Register an offense for calling `merge!` on a method on a variable inside `each_with_object` in `Performance/RedundantMerge`. ([@lumeet][], [@rrosenblum][])
 
 ### Changes
 

lib/rubocop/cop/performance/redundant_merge.rb

@@ -64,7 +64,13 @@ def each_redundant_merge(node)
         end
 
         def value_used_inside_each_with_object?(node, receiver)
-          return false unless receiver.lvar_type?
+          while receiver.respond_to?(:send_type?) && receiver.send_type?
+            receiver, = *receiver
+          end
+
+          unless receiver.respond_to?(:lvar_type?) && receiver.lvar_type?
+            return false
+          end
 
           parent = node.parent
           grandparent = parent.parent if parent.begin_type?

spec/rubocop/cop/performance/redundant_merge_spec.rb

@@ -91,12 +91,40 @@
       expect(cop.offenses).to be_empty
     end
 
-    it 'does not crash when the receiver inside each_object is not a local' \
-       'variable' do
-      inspect_source(cop, ['foo.each_with_object(bar) do |f, hash|',
-                           '  hash[:a].merge!(b: "")',
-                           'end'])
-      expect(cop.offenses).to be_empty
+    it 'autocorrects when receiver uses element reference to the object ' \
+       'built by each_with_object' do
+      source = ['foo.each_with_object(bar) do |f, hash|',
+                '  hash[:a].merge!(b: "")',
+                'end']
+      new_source = autocorrect_source(cop, source)
+
+      expect(new_source).to eq(['foo.each_with_object(bar) do |f, hash|',
+                                '  hash[:a][:b] = ""',
+                                'end'].join("\n"))
+    end
+
+    it 'autocorrects when receiver uses multiple element references to the ' \
+       'object built by each_with_object' do
+      source = ['foo.each_with_object(bar) do |f, hash|',
+                '  hash[:a][:b].merge!(c: "")',
+                'end']
+      new_source = autocorrect_source(cop, source)
+
+      expect(new_source).to eq(['foo.each_with_object(bar) do |f, hash|',
+                                '  hash[:a][:b][:c] = ""',
+                                'end'].join("\n"))
+    end
+
+    it 'autocorrects merge! called on any method on the object built ' \
+       'by each_with_object' do
+      source = ['foo.each_with_object(bar) do |f, hash|',
+                '  hash.bar.merge!(c: "")',
+                'end']
+      new_source = autocorrect_source(cop, source)
+
+      expect(new_source).to eq(['foo.each_with_object(bar) do |f, hash|',
+                                '  hash.bar[:c] = ""',
+                                'end'].join("\n"))
     end
   end