Use handler-specific dependency trackers

lib/cache_digests/dependency_tracker.rb

@@ -1,66 +1,84 @@
 module CacheDigests
   class DependencyTracker
-    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
+    @trackers = Hash.new
 
     def self.find_dependencies(name, template)
-      new(name, template).dependencies
+      @trackers.fetch(template.handler).call(name, template)
     end
 
-    def initialize(name, template)
-      @name, @template = name, template
+    def self.register_tracker(handler, tracker)
+      @trackers[handler] = tracker
     end
 
-    def dependencies
-      render_dependencies + explicit_dependencies
-    rescue ActionView::MissingTemplate
-      [] # File doesn't exist, so no dependencies
+    def self.unregister_tracker(handler)
+      @trackers.delete(handler)
     end
 
-    private
-      attr_reader :name, :template
+    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 source
-        template.source
+      def self.call(name, template)
+        new(name, template).dependencies
       end
-      
-      def directory
-        name.split("/")[0..-2].join("/")
+
+      def initialize(name, template)
+        @name, @template = name, template
       end
 
-      def render_dependencies
-        source.scan(RENDER_DEPENDENCY).
-          collect(&:second).uniq.
+      def dependencies
+        render_dependencies + explicit_dependencies
+      rescue ActionView::MissingTemplate
+        [] # File doesn't exist, so no dependencies
+      end
 
-          # 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}" } }.
+      private
+        attr_reader :name, :template
 
-          # render("headline") => render("message/headline")
-          collect { |name| name.include?("/") ? name : "#{directory}/#{name}" }.
-
-          # replace quotes from string renders
-          collect { |name| name.gsub(/["']/, "") }
-      end
+        def source
+          template.source
+        end
+
+        def directory
+          name.split("/")[0..-2].join("/")
+        end
 
-      def explicit_dependencies
-        source.scan(EXPLICIT_DEPENDENCY).flatten.uniq
-      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
+
+    register_tracker(:erb, ErbTracker)
   end
 end

test/dependency_tracker_test.rb

@@ -0,0 +1,32 @@
+require 'cache_digests/test_helper'
+
+class NeckbeardTracker
+  def self.call(name, template)
+    ["foo/#{name}"]
+  end
+end
+
+class DependencyTrackerTest < MiniTest::Unit::TestCase
+  class FixtureTemplate
+    attr_reader :source, :handler
+
+    def initialize(source, handler)
+      @source, @handler = source, handler
+    end
+  end
+
+  def setup
+    CacheDigests::DependencyTracker.register_tracker(:neckbeard, NeckbeardTracker)
+  end
+
+  def teardown
+    CacheDigests::DependencyTracker.unregister_tracker(:neckbeard)
+  end
+
+  def test_finds_tracker_by_template_handler
+    name = "boo/hoo"
+    template = FixtureTemplate.new("whatevs", :neckbeard)
+    dependencies = CacheDigests::DependencyTracker.find_dependencies(name, template)
+    assert_equal ["foo/boo/hoo"], 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