Enable `Performance/ChainArrayAllocation` cop (#8404)

Merge pull request 8404

.rubocop.yml

@@ -160,6 +160,8 @@ Performance/AncestorsInclude:
   Enabled: false
 Performance/BigDecimalWithNumericArgument:
   Enabled: true
+Performance/ChainArrayAllocation:
+  Enabled: true
 Performance/RedundantSortBlock:
   Enabled: true
 Performance/RedundantStringChars:

lib/jekyll/drops/drop.rb

@@ -139,12 +139,8 @@ module Jekyll
       # Returns an Array of strings which represent method-specific keys.
       def content_methods
         @content_methods ||= (
-          self.class.instance_methods \
-            - Jekyll::Drops::Drop.instance_methods \
-            - NON_CONTENT_METHODS
-        ).map(&:to_s).reject do |method|
-          method.end_with?("=")
-        end
+          self.class.instance_methods - Jekyll::Drops::Drop.instance_methods - NON_CONTENT_METHODS
+        ).map!(&:to_s).tap { |result| result.reject! { |method| method.end_with?("=") } }
       end
 
       # Check if key exists in Drop

lib/jekyll/filters/url_filters.rb

@@ -76,13 +76,16 @@ module Jekyll
 
         parts = [sanitized_baseurl, input]
         Addressable::URI.parse(
-          parts.compact.map { |part| ensure_leading_slash(part.to_s) }.join
+          parts.map! { |part| ensure_leading_slash(part.to_s) }.join
         ).normalize.to_s
       end
 
       def sanitized_baseurl
         site = @context.registers[:site]
-        site.config["baseurl"].to_s.chomp("/")
+        baseurl = site.config["baseurl"]
+        return "" if baseurl.nil?
+
+        baseurl.to_s.chomp("/")
       end
 
       def ensure_leading_slash(input)

lib/jekyll/frontmatter_defaults.rb

@@ -223,7 +223,7 @@ module Jekyll
           Jekyll.logger.warn set.to_s
           nil
         end
-      end.compact
+      end.tap(&:compact!)
     end
 
     # Sanitizes the given path by removing a leading slash

lib/jekyll/readers/post_reader.rb

@@ -57,7 +57,7 @@ module Jekyll
         Document.new(path,
                      :site       => @site,
                      :collection => @site.posts)
-      end.reject(&:nil?)
+      end.tap(&:compact!)
     end
 
     private

lib/jekyll/related_posts.rb

@@ -46,7 +46,7 @@ module Jekyll
     end
 
     def most_recent_posts
-      @most_recent_posts ||= (site.posts.docs.last(11).reverse - [post]).first(10)
+      @most_recent_posts ||= (site.posts.docs.last(11).reverse! - [post]).first(10)
     end
   end
 end

lib/jekyll/renderer.rb

@@ -36,7 +36,7 @@ module Jekyll
     #
     # Returns Array of Converter instances.
     def converters
-      @converters ||= site.converters.select { |c| c.matches(document.extname) }.sort
+      @converters ||= site.converters.select { |c| c.matches(document.extname) }.tap(&:sort!)
     end
 
     # Determine the extname the outputted file should have
@@ -255,7 +255,7 @@ module Jekyll
     def output_exts
       @output_exts ||= converters.map do |c|
         c.output_ext(document.extname)
-      end.compact
+      end.tap(&:compact!)
     end
 
     def liquid_options

lib/jekyll/site.rb

@@ -310,8 +310,9 @@ module Jekyll
     # passed in as argument.
 
     def instantiate_subclasses(klass)
-      klass.descendants.select { |c| !safe || c.safe }.sort.map do |c|
-        c.new(config)
+      klass.descendants.select { |c| !safe || c.safe }.tap do |result|
+        result.sort!
+        result.map! { |c| c.new(config) }
       end
     end