Merge pull request #353 from eugeneius/index_by_index_with_hash_reuse

[Fix #338][Fix #350] Fix a false positive for Rails/IndexBy and Rails/IndexWith
rubocop · Sep 10, 2020 · de09957 · de09957
2 parents fa637ca + d8c62f5
commit de09957
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Showing 5 changed files with 19 additions and 2 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -6,6 +6,7 @@
 
 * [#345](https://github.com/rubocop-hq/rubocop-rails/issues/345): Fix error of `Rails/AfterCommitOverride` on `after_commit` with a lambda. ([@pocke][])
 * [#349](https://github.com/rubocop-hq/rubocop-rails/pull/349): Fix errors of `Rails/UniqueValidationWithoutIndex`. ([@Tietew][])
+* [#338](https://github.com/rubocop-hq/rubocop-rails/issues/338): Fix a false positive for `Rails/IndexBy` and `Rails/IndexWith` when the `each_with_object` hash is used in the transformed key or value. ([@eugeneius][])
 
 ## 2.8.0 (2020-09-04)
 

diff --git a/lib/rubocop/cop/rails/index_by.rb b/lib/rubocop/cop/rails/index_by.rb
@@ -24,7 +24,7 @@ class IndexBy < Cop
           (block
             ({send csend} _ :each_with_object (hash))
             (args (arg $_el) (arg _memo))
-            ({send csend} (lvar _memo) :[]= $_ (lvar _el)))
+            ({send csend} (lvar _memo) :[]= $!`_memo (lvar _el)))
         PATTERN
 
         def_node_matcher :on_bad_to_h, <<~PATTERN

diff --git a/lib/rubocop/cop/rails/index_with.rb b/lib/rubocop/cop/rails/index_with.rb
@@ -27,7 +27,7 @@ class IndexWith < Cop
           (block
             ({send csend} _ :each_with_object (hash))
             (args (arg $_el) (arg _memo))
-            ({send csend} (lvar _memo) :[]= (lvar _el) $_))
+            ({send csend} (lvar _memo) :[]= (lvar _el) $!`_memo))
         PATTERN
 
         def_node_matcher :on_bad_to_h, <<~PATTERN

diff --git a/spec/rubocop/cop/rails/index_by_spec.rb b/spec/rubocop/cop/rails/index_by_spec.rb
@@ -68,6 +68,14 @@
     end
   end
 
+  context 'when the given hash is used in the key' do
+    it 'does not register an offense for `each_with_object`' do
+      expect_no_offenses(<<~RUBY)
+        x.each_with_object({}) { |el, h| h[h[el]] = el }
+      RUBY
+    end
+  end
+
   context 'when `to_h` is given a block' do
     it 'registers an offense for `map { ... }.to_h`' do
       expect_offense(<<~RUBY)

diff --git a/spec/rubocop/cop/rails/index_with_spec.rb b/spec/rubocop/cop/rails/index_with_spec.rb
@@ -69,6 +69,14 @@
       end
     end
 
+    context 'when the given hash is used in the value' do
+      it 'does not register an offense for `each_with_object`' do
+        expect_no_offenses(<<~RUBY)
+          x.each_with_object({}) { |el, h| h[el] = h.count }
+        RUBY
+      end
+    end
+
     context 'when `to_h` is given a block' do
       it 'registers an offense for `map { ... }.to_h`' do
         expect_offense(<<~RUBY)