Also dump object distribution

Gemfile

@@ -2,6 +2,7 @@ source 'https://rubygems.org'
 
 gemspec
 gem 'stackprof', platforms: :mri_21
+gem 'allocation_tracer', platforms: :mri_21
 
 group :test do
   gem 'spy', '0.4.1'

Rakefile

@@ -71,6 +71,20 @@ namespace :profile do
 
 end
 
+namespace :memory do
+
+  desc "Run the liquid memory tracer"
+  task :run do
+    ruby "./performance/memory.rb"
+  end
+
+  desc "Run the liquid memory tracer with strict parsing"
+  task :strict do
+    ruby "./performance/memory.rb strict"
+  end
+
+end
+
 desc "Run example"
 task :example do
   ruby "-w -d -Ilib example/server/server.rb"

lib/liquid/block_body.rb

@@ -68,7 +68,8 @@ module Liquid
     end
 
     def render(context)
-      output = []
+      @output ||= []
+      @output.clear
       context.resource_limits.render_score += @nodelist.length
 
       @nodelist.each do |token|
@@ -87,16 +88,16 @@ module Liquid
           token_output = render_token(token, context)
 
           unless token.is_a?(Block) && token.blank?
-            output << token_output
+            @output << token_output
           end
         rescue MemoryError => e
           raise e
         rescue ::StandardError => e
-          output << context.handle_error(e, token)
+          @output << context.handle_error(e, token)
         end
       end
 
-      output.join
+      @output.join
     end
 
     private

lib/liquid/context.rb

@@ -13,14 +13,13 @@ module Liquid
   #
   #   context['bob']  #=> nil  class Context
   class Context
-    attr_reader :scopes, :errors, :registers, :environments, :resource_limits
+    attr_reader :scopes, :registers, :environments, :resource_limits
     attr_accessor :exception_handler
 
     def initialize(environments = {}, outer_scope = {}, registers = {}, rethrow_errors = false, resource_limits = nil)
       @environments     = [environments].flatten
       @scopes           = [(outer_scope || {})]
       @registers        = registers
-      @errors           = []
       @resource_limits  = resource_limits || ResourceLimits.new(Template.default_resource_limits)
       squash_instance_assigns_with_environments
 
@@ -30,10 +29,14 @@ module Liquid
         self.exception_handler = ->(e) { true }
       end
 
-      @interrupts = []
+      @interrupts = nil
       @filters = []
     end
 
+    def errors
+      @errors ||= []
+    end
+
     def strainer
       @strainer ||= Strainer.create(self, @filters)
     end
@@ -50,17 +53,17 @@ module Liquid
 
     # are there any not handled interrupts?
     def has_interrupt?
-      !@interrupts.empty?
+      @interrupts && !@interrupts.empty?
     end
 
     # push an interrupt to the stack. this interrupt is considered not handled.
     def push_interrupt(e)
-      @interrupts.push(e)
+      (@interrupts ||= []).push(e)
     end
 
     # pop an interrupt from the stack
     def pop_interrupt
-      @interrupts.pop
+      @interrupts.pop if @interrupts
     end
 
 

lib/liquid/variable.rb

@@ -33,7 +33,8 @@ module Liquid
     end
 
     def lax_parse(markup)
-      @filters = []
+      @filters ||= []
+      @filters.clear
       if markup =~ /(#{QuotedFragment})(.*)/om
         name_markup = $1
         filter_markup = $2
@@ -52,7 +53,8 @@ module Liquid
     end
 
     def strict_parse(markup)
-      @filters = []
+      @filters ||= []
+      @filters.clear
       p = Parser.new(markup)
 
       @name = Expression.parse(p.expression)

lib/liquid/variable_lookup.rb

@@ -10,21 +10,20 @@ module Liquid
     end
 
     def initialize(markup)
-      lookups = markup.scan(VariableParser)
+      @lookups = markup.scan(VariableParser)
 
-      name = lookups.shift
+      name = @lookups.shift
       if name =~ SQUARE_BRACKETED
         name = Expression.parse($1)
       end
       @name = name
 
-      @lookups = lookups
       @command_flags = 0
 
       @lookups.each_index do |i|
-        lookup = lookups[i]
+        lookup = @lookups[i]
         if lookup =~ SQUARE_BRACKETED
-          lookups[i] = Expression.parse($1)
+          @lookups[i] = Expression.parse($1)
         elsif COMMAND_METHODS.include?(lookup)
           @command_flags |= 1 << i
         end

performance/memory.rb

@@ -0,0 +1,19 @@
+at_exit do
+  p 'Objects distribution:'
+  require 'pp'
+  pp ObjectSpace.count_objects
+end
+
+require 'allocation_tracer' rescue fail("install allocation_tracer extension/gem")
+require File.dirname(__FILE__) + '/theme_runner'
+
+Liquid::Template.error_mode = ARGV.first.to_sym if ARGV.first
+profiler = ThemeRunner.new
+
+require 'allocation_tracer/trace'
+
+puts "Profiling memory usage..."
+
+200.times do
+  profiler.run
+end

test/unit/context_unit_test.rb

@@ -465,6 +465,7 @@ class ContextUnitTest < Minitest::Test
     mock_empty = Spy.on_instance_method(Array, :empty?)
     mock_has_interrupt = Spy.on(@context, :has_interrupt?).and_call_through
 
+    @context.push_interrupt(StandardError.new)
     @context.has_interrupt?
 
     refute mock_any.has_been_called?