Implement custom delegators for drop methods (#8183)

Merge pull request 8183

benchmark/static-drop-vs-forwarded.rb

@@ -0,0 +1,83 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+require "forwardable"
+require "colorator"
+require "liquid"
+require "benchmark/ips"
+require "memory_profiler"
+
+# Set up (memory) profiler
+
+class Profiler
+  def self.run
+    yield new(ARGV[0] || 10_000)
+  end
+
+  def initialize(count)
+    @count = count.to_i
+  end
+
+  def report(label, color, &block)
+    prof_report = MemoryProfiler.report { @count.to_i.times(&block) }
+
+    allocated_memory  = prof_report.scale_bytes(prof_report.total_allocated_memsize)
+    allocated_objects = prof_report.total_allocated
+    retained_memory   = prof_report.scale_bytes(prof_report.total_retained_memsize)
+    retained_objects  = prof_report.total_retained
+
+    puts <<~MSG.send(color)
+      With #{label} calls
+
+      Total allocated: #{allocated_memory} (#{allocated_objects} objects)
+      Total retained:  #{retained_memory} (#{retained_objects} objects)
+    MSG
+  end
+end
+
+# Set up stage
+
+class Drop < Liquid::Drop
+  def initialize(obj)
+    @obj = obj
+  end
+end
+
+class ForwardDrop < Drop
+  extend Forwardable
+  def_delegators :@obj, :name
+end
+
+class StaticDrop < Drop
+  def name
+    @obj.name
+  end
+end
+
+class Document
+  def name
+    "lipsum"
+  end
+end
+
+# Set up actors
+
+document = Document.new
+alpha    = ForwardDrop.new(document)
+beta     = StaticDrop.new(document)
+count    = ARGV[0] || 10_000
+
+# Run profilers
+puts "\nMemory profiles for #{count} calls to invoke drop key:"
+Profiler.run do |x|
+  x.report("forwarded", :cyan) { alpha["name"] }
+  x.report("static", :green) { beta["name"] }
+end
+
+# Benchmark
+puts "\nBenchmarking the two scenarios..."
+Benchmark.ips do |x|
+  x.report("forwarded".cyan) { alpha["name"] }
+  x.report("static".green) { beta["name"] }
+  x.compare!
+end

lib/jekyll/drops/collection_drop.rb

@@ -7,10 +7,10 @@ module Jekyll
 
       mutable false
 
-      def_delegator  :@obj, :write?, :output
+      delegate_method_as :write?, :output
-      def_delegators :@obj, :label, :docs, :files, :directory, :relative_directory
+      delegate_methods :label, :docs, :files, :directory, :relative_directory
 
-      private def_delegator :@obj, :metadata, :fallback_data
+      private delegate_method_as :metadata, :fallback_data
 
       def to_s
         docs.to_s

lib/jekyll/drops/document_drop.rb

@@ -11,10 +11,11 @@ module Jekyll
 
       mutable false
 
-      def_delegator :@obj, :relative_path, :path
+      delegate_method_as :relative_path, :path
-      def_delegators :@obj, :id, :output, :content, :to_s, :relative_path, :url, :date
+      private delegate_method_as :data, :fallback_data
 
-      private def_delegator :@obj, :data, :fallback_data
+      delegate_methods :id, :output, :content, :to_s, :relative_path, :url, :date
+      data_delegators "title", "categories", "tags"
 
       def collection
         @obj.collection.label
@@ -64,18 +65,6 @@ module Jekyll
           result[key] = doc[key] unless NESTED_OBJECT_FIELD_BLACKLIST.include?(key)
         end
       end
-
-      def title
-        @obj.data["title"]
-      end
-
-      def categories
-        @obj.data["categories"]
-      end
-
-      def tags
-        @obj.data["tags"]
-      end
     end
   end
 end

lib/jekyll/drops/drop.rb

@@ -7,6 +7,7 @@ module Jekyll
 
       NON_CONTENT_METHODS = [:fallback_data, :collapse_document].freeze
 
+      class << self
         # Get or set whether the drop class is mutable.
         # Mutability determines whether or not pre-defined fields may be
         # overwritten.
@@ -14,14 +15,67 @@ module Jekyll
         # is_mutable - Boolean set mutability of the class (default: nil)
         #
         # Returns the mutability of the class
-      def self.mutable(is_mutable = nil)
+        def mutable(is_mutable = nil)
           @is_mutable = is_mutable || false
         end
 
-      def self.mutable?
+        def mutable?
           @is_mutable
         end
 
+        # public delegation helper methods that calls onto Drop's instance
+        # variable `@obj`.
+
+        # Generate private Drop instance_methods for each symbol in the given list.
+        #
+        # Returns nothing.
+        def private_delegate_methods(*symbols)
+          symbols.each { |symbol| private delegate_method(symbol) }
+          nil
+        end
+
+        # Generate public Drop instance_methods for each symbol in the given list.
+        #
+        # Returns nothing.
+        def delegate_methods(*symbols)
+          symbols.each { |symbol| delegate_method(symbol) }
+          nil
+        end
+
+        # Generate public Drop instance_method for given symbol that calls `@obj.<sym>`.
+        #
+        # Returns delegated method symbol.
+        def delegate_method(symbol)
+          define_method(symbol) { @obj.send(symbol) }
+        end
+
+        # Generate public Drop instance_method named `delegate` that calls `@obj.<original>`.
+        #
+        # Returns delegated method symbol.
+        def delegate_method_as(original, delegate)
+          define_method(delegate) { @obj.send(original) }
+        end
+
+        # Generate public Drop instance_methods for each string entry in the given list.
+        # The generated method(s) access(es) `@obj`'s data hash.
+        #
+        # Returns nothing.
+        def data_delegators(*strings)
+          strings.each do |key|
+            data_delegator(key) if key.is_a?(String)
+          end
+          nil
+        end
+
+        # Generate public Drop instance_methods for given string `key`.
+        # The generated method access(es) `@obj`'s data hash.
+        #
+        # Returns method symbol.
+        def data_delegator(key)
+          define_method(key.to_sym) { @obj.data[key] }
+        end
+      end
+
       # Create a new Drop
       #
       # obj - the Jekyll Site, Collection, or Document required by the

lib/jekyll/drops/site_drop.rb

@@ -7,10 +7,10 @@ module Jekyll
 
       mutable false
 
-      def_delegator  :@obj, :site_data, :data
+      delegate_method_as :site_data, :data
-      def_delegators :@obj, :time, :pages, :static_files, :tags, :categories
+      delegate_methods :time, :pages, :static_files, :tags, :categories
 
-      private def_delegator :@obj, :config, :fallback_data
+      private delegate_method_as :config, :fallback_data
 
       def [](key)
         if key != "posts" && @obj.collections.key?(key)

lib/jekyll/drops/static_file_drop.rb

@@ -4,11 +4,11 @@ module Jekyll
   module Drops
     class StaticFileDrop < Drop
       extend Forwardable
-      def_delegators :@obj, :name, :extname, :modified_time, :basename
+      delegate_methods   :name, :extname, :modified_time, :basename
-      def_delegator :@obj, :relative_path, :path
+      delegate_method_as :relative_path, :path
-      def_delegator :@obj, :type, :collection
+      delegate_method_as :type, :collection
 
-      private def_delegator :@obj, :data, :fallback_data
+      private delegate_method_as :data, :fallback_data
     end
   end
 end

lib/jekyll/drops/url_drop.rb

@@ -7,8 +7,8 @@ module Jekyll
 
       mutable false
 
-      def_delegator :@obj, :cleaned_relative_path, :path
+      delegate_method :output_ext
-      def_delegator :@obj, :output_ext, :output_ext
+      delegate_method_as :cleaned_relative_path, :path
 
       def collection
         @obj.collection.label