Merge pull request #19 from dasch/refactor-dependency-tracking

Allow registering custom dependency trackers

Gemfile.lock

@@ -3,43 +3,48 @@ PATH
   specs:
     cache_digests (0.2.0)
       actionpack (>= 3.2)
+      thread_safe
 
 GEM
   remote: https://rubygems.org/
   specs:
-    actionpack (3.2.8)
-      activemodel (= 3.2.8)
-      activesupport (= 3.2.8)
+    actionpack (3.2.12)
+      activemodel (= 3.2.12)
+      activesupport (= 3.2.12)
       builder (~> 3.0.0)
       erubis (~> 2.7.0)
       journey (~> 1.0.4)
-      rack (~> 1.4.0)
+      rack (~> 1.4.5)
       rack-cache (~> 1.2)
       rack-test (~> 0.6.1)
-      sprockets (~> 2.1.3)
-    activemodel (3.2.8)
-      activesupport (= 3.2.8)
+      sprockets (~> 2.2.1)
+    activemodel (3.2.12)
+      activesupport (= 3.2.12)
       builder (~> 3.0.0)
-    activesupport (3.2.8)
+    activesupport (3.2.12)
       i18n (~> 0.6)
       multi_json (~> 1.0)
-    builder (3.0.3)
+    atomic (1.0.1)
+    builder (3.0.4)
     erubis (2.7.0)
     hike (1.2.1)
     i18n (0.6.1)
     journey (1.0.4)
     minitest (2.12.1)
-    multi_json (1.3.6)
-    rack (1.4.1)
+    multi_json (1.6.1)
+    rack (1.4.5)
     rack-cache (1.2)
       rack (>= 0.4)
     rack-test (0.6.2)
       rack (>= 1.0)
     rake (0.9.2.2)
-    sprockets (2.1.3)
+    sprockets (2.2.2)
       hike (~> 1.2)
+      multi_json (~> 1.0)
       rack (~> 1.0)
       tilt (~> 1.1, != 1.3.0)
+    thread_safe (0.1.0)
+      atomic
     tilt (1.3.3)
 
 PLATFORMS

cache_digests.gemspec

@@ -8,6 +8,7 @@ Gem::Specification.new do |s|
   s.required_ruby_version = '>= 1.9'
 
   s.add_dependency 'actionpack', '>= 3.2'
+  s.add_dependency 'thread_safe'
 
   s.add_development_dependency 'rake'
   s.add_development_dependency 'minitest'

lib/cache_digests/dependency_tracker.rb

@@ -0,0 +1,89 @@
+require 'thread_safe'
+
+module CacheDigests
+  class DependencyTracker
+    @trackers = ThreadSafe::Cache.new
+
+    def self.find_dependencies(name, template)
+      tracker = @trackers[template.handler]
+
+      if tracker.present?
+        tracker.call(name, template)
+      else
+        []
+      end
+    end
+
+    def self.register_tracker(extension, tracker)
+      handler = ActionView::Template.handler_for_extension(extension)
+      @trackers[handler] = tracker
+    end
+
+    def self.remove_tracker(handler)
+      @trackers.delete(handler)
+    end
+
+    class ERBTracker
+      EXPLICIT_DEPENDENCY = /# Template Dependency: (\S+)/
+
+      # Matches:
+      #   render partial: "comments/comment", collection: commentable.comments
+      #   render "comments/comments"
+      #   render 'comments/comments'
+      #   render('comments/comments')
+      #
+      #   render(@topic)         => render("topics/topic")
+      #   render(topics)         => render("topics/topic")
+      #   render(message.topics) => render("topics/topic")
+      RENDER_DEPENDENCY = /
+        render\s*                     # render, followed by optional whitespace
+        \(?                           # start an optional parenthesis for the render call
+        (partial:|:partial\s+=>)?\s*  # naming the partial, used with collection -- 1st capture
+        ([@a-z"'][@a-z_\/\."']+)      # the template name itself -- 2nd capture
+      /x
+
+      def self.call(name, template)
+        new(name, template).dependencies
+      end
+
+      def initialize(name, template)
+        @name, @template = name, template
+      end
+
+      def dependencies
+        render_dependencies + explicit_dependencies
+      end
+
+      private
+        attr_reader :name, :template
+
+        def source
+          template.source
+        end
+
+        def directory
+          name.split("/")[0..-2].join("/")
+        end
+
+        def render_dependencies
+          source.scan(RENDER_DEPENDENCY).
+            collect(&:second).uniq.
+
+            # render(@topic)         => render("topics/topic")
+            # render(topics)         => render("topics/topic")
+            # render(message.topics) => render("topics/topic")
+            collect { |name| name.sub(/\A@?([a-z]+\.)*([a-z_]+)\z/) { "#{$2.pluralize}/#{$2.singularize}" } }.
+
+            # render("headline") => render("message/headline")
+            collect { |name| name.include?("/") ? name : "#{directory}/#{name}" }.
+
+            # replace quotes from string renders
+            collect { |name| name.gsub(/["']/, "") }
+        end
+
+        def explicit_dependencies
+          source.scan(EXPLICIT_DEPENDENCY).flatten.uniq
+        end
+    end
+  end
+end

lib/cache_digests/engine.rb

@@ -13,6 +13,7 @@ class Engine < ::Rails::Engine
 
       config.to_prepare do
         CacheDigests::TemplateDigestor.logger = Rails.logger
+        DependencyTracker.register_tracker :erb, DependencyTracker::ERBTracker
       end
     end
   end

lib/cache_digests/template_digestor.rb

@@ -1,27 +1,10 @@
 require 'active_support/core_ext'
 require 'active_support/cache'
 require 'logger'
+require 'cache_digests/dependency_tracker'
 
 module CacheDigests
   class TemplateDigestor
-    EXPLICIT_DEPENDENCY = /# Template Dependency: (\S+)/
-
-    # Matches:
-    #   render partial: "comments/comment", collection: commentable.comments
-    #   render "comments/comments"
-    #   render 'comments/comments'
-    #   render('comments/comments')
-    #
-    #   render(@topic)         => render("topics/topic")
-    #   render(topics)         => render("topics/topic")
-    #   render(message.topics) => render("topics/topic")
-    RENDER_DEPENDENCY = /
-      render\s*                     # render, followed by optional whitespace
-      \(?                           # start an optional parenthesis for the render call
-      (partial:|:partial\s+=>)?\s*  # naming the partial, used with collection -- 1st capture
-      ([@a-z"'][@a-z_\/\."']+)      # the template name itself -- 2nd capture
-    /x
-
     cattr_accessor(:cache) { ActiveSupport::Cache::MemoryStore.new }
     cattr_accessor(:cache_prefix)
 
@@ -51,7 +34,7 @@ def digest
     end
 
     def dependencies
-      render_dependencies + explicit_dependencies
+      DependencyTracker.find_dependencies(name, template)
     rescue ActionView::MissingTemplate
       [] # File doesn't exist, so no dependencies
     end
@@ -68,18 +51,17 @@ def logical_name
         name.gsub(%r|/_|, "/")
       end
 
-      def directory
-        name.split("/")[0..-2].join("/")
-      end
-
       def partial?
         options[:partial] || name.include?("/_")
       end
 
       def source
-        @source ||= finder.find(logical_name, [], partial?, formats: [ format ]).source
+        template.source
       end
 
+      def template
+        @template ||= finder.find(logical_name, [], partial?, formats: [ format ])
+      end
 
       def dependency_digest
         template_digests = dependencies.collect do |template_name|
@@ -89,26 +71,6 @@ def dependency_digest
         (template_digests + injected_dependencies).join("-")
       end
 
-      def render_dependencies
-        source.scan(RENDER_DEPENDENCY).
-          collect(&:second).uniq.
-
-          # render(@topic)         => render("topics/topic")
-          # render(topics)         => render("topics/topic")
-          # render(message.topics) => render("topics/topic")
-          collect { |name| name.sub(/\A@?([a-z]+\.)*([a-z_]+)\z/) { "#{$2.pluralize}/#{$2.singularize}" } }.
-
-          # render("headline") => render("message/headline")
-          collect { |name| name.include?("/") ? name : "#{directory}/#{name}" }.
-
-          # replace quotes from string renders
-          collect { |name| name.gsub(/["']/, "") }
-      end
-
-      def explicit_dependencies
-        source.scan(EXPLICIT_DEPENDENCY).flatten.uniq
-      end
-
       def injected_dependencies
         Array.wrap(options[:dependencies])
       end

test/dependency_tracker_test.rb

@@ -0,0 +1,49 @@
+require 'cache_digests/test_helper'
+
+class NeckbeardTracker
+  def self.call(name, template)
+    ["foo/#{name}"]
+  end
+end
+
+module ActionView
+  class Template
+    def self.handler_for_extension(extension)
+      extension
+    end
+  end
+end
+
+class DependencyTrackerTest < MiniTest::Unit::TestCase
+  class FakeTemplate
+    attr_reader :source, :handler
+
+    def initialize(source, handler)
+      @source, @handler = source, handler
+    end
+  end
+
+  def tracker
+    CacheDigests::DependencyTracker
+  end
+
+  def setup
+    tracker.register_tracker(:neckbeard, NeckbeardTracker)
+  end
+
+  def teardown
+    tracker.remove_tracker(:neckbeard)
+  end
+
+  def test_finds_tracker_by_template_handler
+    template = FakeTemplate.new("boo/hoo", :neckbeard)
+    dependencies = tracker.find_dependencies("boo/hoo", template)
+    assert_equal ["foo/boo/hoo"], dependencies
+  end
+
+  def test_returns_empty_array_if_no_tracker_registered_for_handler
+    template = FakeTemplate.new("boo/hoo", :hater)
+    dependencies = tracker.find_dependencies("boo/hoo", template)
+    assert_equal [], dependencies
+  end
+end

test/template_digestor_test.rb

@@ -7,10 +7,11 @@ class MissingTemplate < StandardError
 end
 
 class FixtureTemplate
-  attr_reader :source
+  attr_reader :source, :handler
 
-  def initialize(template_path)
+  def initialize(template_path, handler = :erb)
     @source = File.read(template_path)
+    @handler = handler
   rescue Errno::ENOENT
     raise ActionView::MissingTemplate
   end
@@ -28,12 +29,14 @@ def find(logical_name, keys, partial, options)
 class TemplateDigestorTest < MiniTest::Unit::TestCase
   def setup
     FileUtils.cp_r FixtureFinder::FIXTURES_DIR, FixtureFinder::TMP_DIR
+    CacheDigests::DependencyTracker.register_tracker :erb, CacheDigests::DependencyTracker::ERBTracker
   end
 
   def teardown
     FileUtils.rm_r FixtureFinder::TMP_DIR
     CacheDigests::TemplateDigestor.cache.clear
     CacheDigests::TemplateDigestor.cache_prefix = nil
+    CacheDigests::DependencyTracker.remove_tracker :erb
   end
 
   def test_top_level_change_reflected