Add Performance/StringIdentifierArgument rule

It was added in rubocop-performance 1.13.0. We were already applying it
in most places.

We aren't adding it for performance reasons but in order to make the
code more consistent.

.rubocop.yml

@@ -224,6 +224,9 @@ Performance/EndWith:
 Performance/StartWith:
   Enabled: true
 
+Performance/StringIdentifierArgument:
+  Enabled: true
+
 Performance/Sum:
   Enabled: true
 

app/controllers/concerns/flag_actions.rb

@@ -17,9 +17,9 @@ module FlagActions
 
     def flaggable
       if resource_model.to_s == "Budget::Investment"
-        instance_variable_get("@investment")
+        instance_variable_get(:@investment)
       elsif resource_model.to_s == "Legislation::Proposal"
-        instance_variable_get("@proposal")
+        instance_variable_get(:@proposal)
       else
         instance_variable_get("@#{resource_model.to_s.downcase}")
       end

app/controllers/concerns/polymorphic.rb

@@ -3,9 +3,9 @@ module Polymorphic
 
     def resource
       if resource_model.to_s == "Budget::Investment"
-        @resource ||= instance_variable_get("@investment")
+        @resource ||= instance_variable_get(:@investment)
       elsif resource_model.to_s == "Legislation::Proposal"
-        @resource ||= instance_variable_get("@proposal")
+        @resource ||= instance_variable_get(:@proposal)
       else
         @resource ||= instance_variable_get("@#{resource_name}")
       end

app/models/concerns/skip_validation.rb

@@ -13,7 +13,7 @@ module SkipValidation
 
       _validate_callbacks.each do |callback|
         if callback.raw_filter.is_a?(validator_class)
-          callback.raw_filter.instance_variable_set("@attributes", callback.raw_filter.attributes - [field])
+          callback.raw_filter.instance_variable_set(:@attributes, callback.raw_filter.attributes - [field])
         end
       end
     end

app/models/direct_upload.rb

@@ -22,7 +22,7 @@ class DirectUpload
       # Refactor
       @relation = if @resource.respond_to?(:images) &&
                      ((@attachment.present? && !@attachment.content_type.match(/pdf/)) || @cached_attachment.present?)
-                    @resource.images.send("build", relation_attributtes)
+                    @resource.images.send(:build, relation_attributtes)
                   elsif @resource.class.reflections[@resource_relation].macro == :has_one
                     @resource.send("build_#{resource_relation}", relation_attributtes)
                   else

lib/comment_tree.rb

@@ -19,7 +19,7 @@ class CommentTree
   end
 
   def base_comments
-    if @valuations && commentable.respond_to?("valuations")
+    if @valuations && commentable.respond_to?(:valuations)
       commentable.valuations
     else
       commentable.comments

spec/models/related_content_spec.rb

@@ -79,11 +79,11 @@ describe RelatedContent do
       create(:related_content, parent_relationable: parent_relationable, child_relationable: child_relationable, author: build(:user))
 
       2.times do
-        related_content.send("score_positive", build(:user))
+        related_content.send(:score_positive, build(:user))
       end
 
       6.times do
-        related_content.send("score_negative", build(:user))
+        related_content.send(:score_negative, build(:user))
       end
     end
 

spec/shared/system/relationable.rb

@@ -173,11 +173,11 @@ shared_examples "relationable" do |relationable_model_name|
     related_content = create(:related_content, parent_relationable: relationable, child_relationable: related1, author: build(:user))
 
     2.times do
-      related_content.send("score_positive", build(:user))
+      related_content.send(:score_positive, build(:user))
     end
 
     6.times do
-      related_content.send("score_negative", build(:user))
+      related_content.send(:score_negative, build(:user))
     end
 
     login_as(user)