Fix a false negative for Performance/ChainArrayAllocation aware of …

…`first(do_something).uniq` This PR fixes a false negative for `Performance/ChainArrayAllocation` when using `array.first(do_something).uniq`.
rubocop · Jun 15, 2022 · 0837b87 · 0837b87
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diff --git a/changelog/fix_false_negative_for_performance_chain_array_allocation.md b/changelog/fix_false_negative_for_performance_chain_array_allocation.md
@@ -0,0 +1 @@
+* [#294](https://github.com/rubocop/rubocop-performance/pull/294): Fix a false negative for `Performance/ChainArrayAllocation` when using `array.first(do_something).uniq`. ([@koic][])
diff --git a/lib/rubocop/cop/performance/chain_array_allocation.rb b/lib/rubocop/cop/performance/chain_array_allocation.rb
@@ -53,7 +53,7 @@ class ChainArrayAllocation < Base
 
         def_node_matcher :chain_array_allocation?, <<~PATTERN
           (send {
-            (send _ $%RETURN_NEW_ARRAY_WHEN_ARGS {int lvar ivar cvar gvar})
+            (send _ $%RETURN_NEW_ARRAY_WHEN_ARGS {int lvar ivar cvar gvar send})
             (block (send _ $%ALWAYS_RETURNS_NEW_ARRAY) ...)
             (send _ $%RETURNS_NEW_ARRAY ...)
           } $%HAS_MUTATION_ALTERNATIVE ...)

diff --git a/spec/rubocop/cop/performance/chain_array_allocation_spec.rb b/spec/rubocop/cop/performance/chain_array_allocation_spec.rb
@@ -23,6 +23,13 @@
                                     ^^^^^ Use unchained `first` and `uniq!` (followed by `return array` if required) instead of chaining `first...uniq`.
       RUBY
     end
+
+    it 'registers an offense for `first(do_something).uniq`' do
+      expect_offense(<<~RUBY)
+        [1, 2, 3, 4].first(do_something).uniq
+                                        ^^^^^ Use unchained `first` and `uniq!` (followed by `return array` if required) instead of chaining `first...uniq`.
+      RUBY
+    end
   end
 
   describe 'methods that only return an array with no block' do