Make Rails/FindBy aware of safe navigation operator

Author: hoshinotsuyoshi

lib/rubocop/cop/rails/find_by.rb

@@ -20,7 +20,7 @@ class FindBy < Cop
         TARGET_SELECTORS = %i[first take].freeze
 
         def_node_matcher :where_first?, <<-PATTERN
-          (send (send _ :where ...) {:first :take})
+          (send ({send csend} _ :where ...) {:first :take})
         PATTERN
 
         def on_send(node)
@@ -32,6 +32,7 @@ def on_send(node)
           add_offense(node, location: range,
                             message: format(MSG, method: node.method_name))
         end
+        alias on_csend on_send
 
         def autocorrect(node)
           # Don't autocorrect where(...).first, because it can return different

spec/rubocop/cop/rails/find_by_spec.rb

@@ -28,4 +28,25 @@
   it 'does not register an offense when using find_by' do
     expect_no_offenses('User.find_by(id: x)')
   end
+
+  it 'autocorrects where.take to find_by' do
+    new_source = autocorrect_source('User.where(id: x).take')
+
+    expect(new_source).to eq('User.find_by(id: x)')
+  end
+
+  it 'does not autocorrect where.first' do
+    new_source = autocorrect_source('User.where(id: x).first')
+
+    expect(new_source).to eq('User.where(id: x).first')
+  end
+
+  context 'when using safe navigation operator', :ruby23 do
+    it 'registers an offense when using `#first`' do
+      expect_offense(<<-RUBY.strip_indent)
+        User&.where(id: x).first
+              ^^^^^^^^^^^^^^^^^^ Use `find_by` instead of `where.first`.
+      RUBY
+    end
+  end
 end