From 445284906476f03acf37cab2b7dc265a985531c3 Mon Sep 17 00:00:00 2001
From: Daniel Schierbeck <dasch@zendesk.com>
Date: Mon, 17 Dec 2012 21:26:55 +0100
Subject: [PATCH] Return an empty array if no tracker is found

---
 actionpack/lib/action_view/dependency_tracker.rb    |  9 +++++++--
 actionpack/test/template/dependency_tracker_test.rb | 11 +++++++++--
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/actionpack/lib/action_view/dependency_tracker.rb b/actionpack/lib/action_view/dependency_tracker.rb
index 3478e34fe3..b817b9bdd7 100644
--- a/actionpack/lib/action_view/dependency_tracker.rb
+++ b/actionpack/lib/action_view/dependency_tracker.rb
@@ -5,8 +5,13 @@ class DependencyTracker
     @trackers = ThreadSafe::Cache.new
 
     def self.find_dependencies(name, template)
-      handler = template.handler
-      @trackers.fetch(handler).call(name, template)
+      tracker = @trackers[template.handler]
+
+      if tracker.present?
+        tracker.call(name, template)
+      else
+        []
+      end
     end
 
     def self.register_tracker(handler, tracker)
diff --git a/actionpack/test/template/dependency_tracker_test.rb b/actionpack/test/template/dependency_tracker_test.rb
index 5b2ec0eb2d..714e2d6b29 100644
--- a/actionpack/test/template/dependency_tracker_test.rb
+++ b/actionpack/test/template/dependency_tracker_test.rb
@@ -3,6 +3,7 @@
 
 class DependencyTrackerTest < ActionView::TestCase
   Neckbeard = Class.new
+  Bowtie = Class.new
 
   class NeckbeardTracker
     def self.call(name, template)
@@ -13,8 +14,8 @@ def self.call(name, template)
   class FakeTemplate
     attr_reader :source, :handler
 
-    def initialize(source)
-      @source, @handler = source, Neckbeard
+    def initialize(source, handler = Neckbeard)
+      @source, @handler = source, handler
     end
   end
 
@@ -35,4 +36,10 @@ def test_finds_tracker_by_template_handler
     dependencies = tracker.find_dependencies("boo/hoo", template)
     assert_equal ["foo/boo/hoo"], dependencies
   end
+
+  def test_returns_empty_array_if_no_tracker_is_found
+    template = FakeTemplate.new("boo/hoo", Bowtie)
+    dependencies = tracker.find_dependencies("boo/hoo", template)
+    assert_equal [], dependencies
+  end
 end
-- 
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