Bypass rendering via Liquid unless required (jekyll#6735)

Merge pull request 6735

benchmark/conditional_liquid.rb

@@ -0,0 +1,101 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+require "liquid"
+require "benchmark/ips"
+
+# Test if processing content string without any Liquid constructs, via Liquid,
+# is slower than checking whether constructs exist ( using `String#include?` )
+# and return-ing the "plaintext" content string as is..
+#
+# Ref: https://github.com/jekyll/jekyll/pull/6735
+
+# Sample contents
+WITHOUT_LIQUID = <<-TEXT.freeze
+Lorem ipsum dolor sit amet, consectetur adipiscing elit. Fusce auctor libero at
+pharetra tempus. Etiam bibendum magna et metus fermentum, eu cursus lorem
+mattis. Curabitur vel dui et lacus rutrum suscipit et eget neque.
+
+Nullam luctus fermentum est id blandit. Phasellus consectetur ullamcorper
+ligula, at finibus eros laoreet id. Etiam sit amet est in libero efficitur
+tristique. Ut nec magna augue. Quisque ut fringilla lacus, ac dictum enim.
+Aliquam vel ornare mauris. Suspendisse ornare diam tempor nulla facilisis
+aliquet. Sed ultrices placerat ultricies.
+TEXT
+
+WITH_LIQUID = <<-LIQUID.freeze
+Lorem ipsum dolor sit amet, consectetur adipiscing elit. Fusce auctor libero at
+pharetra tempus. {{ author }} et metus fermentum, eu cursus lorem
+mattis. Curabitur vel dui et lacus rutrum suscipit et eget neque.
+
+Nullam luctus fermentum est id blandit. Phasellus consectetur ullamcorper
+ligula, {% if author == "Jane Doe" %} at finibus eros laoreet id. {% else %}
+Etiam sit amet est in libero efficitur.{% endif %}
+tristique. Ut nec magna augue. Quisque ut fringilla lacus, ac dictum enim.
+Aliquam vel ornare mauris. Suspendisse ornare diam tempor nulla facilisis
+aliquet. Sed ultrices placerat ultricies.
+LIQUID
+
+WITH_JUST_LIQUID_VAR = <<-LIQUID.freeze
+Lorem ipsum dolor sit amet, consectetur adipiscing elit. Fusce auctor libero at
+pharetra tempus. et metus fermentum, eu cursus lorem, ac dictum enim.
+mattis. Curabitur vel dui et lacus rutrum suscipit et {{ title }} neque.
+
+Nullam luctus fermentum est id blandit. Phasellus consectetur ullamcorper
+ligula, at finibus eros laoreet id. Etiam sit amet est in libero efficitur.
+tristique. Ut nec magna augue. {{ author }} Quisque ut fringilla lacus
+Aliquam vel ornare mauris. Suspendisse ornare diam tempor nulla facilisis
+aliquet. Sed ultrices placerat ultricies.
+LIQUID
+
+SUITE = {
+  :"plain text"  => WITHOUT_LIQUID,
+  :"tags n vars" => WITH_LIQUID,
+  :"just vars"   => WITH_JUST_LIQUID_VAR,
+}.freeze
+
+# Mimic how Jekyll's LiquidRenderer would process a non-static file, with
+# some dummy payload
+def always_liquid(content)
+  Liquid::Template.error_mode = :warn
+  Liquid::Template.parse(content, :line_numbers => true).render(
+    "author" => "John Doe",
+    "title"  => "FooBar"
+  )
+end
+
+# Mimic how the proposed change would first execute a couple of checks and
+# proceed to process with Liquid if necessary
+def conditional_liquid(content)
+  return content if content.nil? || content.empty?
+  return content unless content.include?("{%") || content.include?("{{")
+  always_liquid(content)
+end
+
+# Test https://github.com/jekyll/jekyll/pull/6735#discussion_r165499868
+# ------------------------------------------------------------------------
+def check_with_regex(content)
+  !content.to_s.match?(%r!{[{%]!)
+end
+
+def check_with_builtin(content)
+  content.include?("{%") || content.include?("{{")
+end
+
+SUITE.each do |key, text|
+  Benchmark.ips do |x|
+    x.report("regex-check   - #{key}") { check_with_regex(text) }
+    x.report("builtin-check - #{key}") { check_with_builtin(text) }
+    x.compare!
+  end
+end
+# ------------------------------------------------------------------------
+
+# Let's roll!
+SUITE.each do |key, text|
+  Benchmark.ips do |x|
+    x.report("always thru liquid - #{key}") { always_liquid(text) }
+    x.report("conditional liquid - #{key}") { conditional_liquid(text) }
+    x.compare!
+  end
+end

lib/jekyll/convertible.rb

@@ -165,9 +165,9 @@ def coffeescript_file?
 
     # Determine whether the file should be rendered with Liquid.
     #
-    # Always returns true.
+    # Returns true if the file has Liquid Tags or Variables, false otherwise.
     def render_with_liquid?
-      true
+      Jekyll::Utils.has_liquid_construct?(content)
     end
 
     # Determine whether the file should be placed into layouts.

lib/jekyll/document.rb

@@ -157,9 +157,10 @@ def coffeescript_file?
     # Determine whether the file should be rendered with Liquid.
     #
     # Returns false if the document is either an asset file or a yaml file,
+    #   or if the document doesn't contain any Liquid Tags or Variables,
     #   true otherwise.
     def render_with_liquid?
-      !(coffeescript_file? || yaml_file?)
+      !(coffeescript_file? || yaml_file? || !Utils.has_liquid_construct?(content))
     end
 
     # Determine whether the file should be rendered with a layout.

lib/jekyll/renderer.rb

@@ -77,7 +77,7 @@ def render_document
       end
 
       Jekyll.logger.debug "Rendering Markup:", document.relative_path
-      output = convert(output)
+      output = convert(output.to_s)
       document.content = output
 
       if document.place_in_layout?

lib/jekyll/utils.rb

@@ -147,6 +147,14 @@ def has_yaml_header?(file)
     rescue EOFError
       false
     end
+
+    # Determine whether the given content string contains Liquid Tags or Vaiables
+    #
+    # Returns true is the string contains sequences of `{%` or `{{`
+    def has_liquid_construct?(content)
+      return false if content.nil? || content.empty?
+      content.include?("{%") || content.include?("{{")
+    end
     # rubocop: enable PredicateName
 
     # Slugify a filename or title.