Bust the template digest cache key when details are changed

Since the lookup details will influence which template is resolved, they
need to be included in the cache key -- otherwise two different
templates may erroneously share the same digest value.

actionview/CHANGELOG.md

@@ -13,6 +13,12 @@
 
     *Josh Lauer*, *Justin Ridgewell*
 
+*   Fixed a bug where the lookup details were not being taken into account
+    when caching the digest of a template - changes to the details now
+    cause a different cache key to be used.
+
+    *Daniel Schierbeck*
+
 *   Added an `extname` hash option for `javascript_include_tag` method.
 
     Before:

actionview/lib/action_view/digestor.rb

@@ -10,7 +10,10 @@ class Digestor
 
     class << self
       def digest(name, format, finder, options = {})
-        cache_key = ([name, format] + Array.wrap(options[:dependencies])).join('.')
+        details_key = finder.details_key.hash
+        dependencies = Array.wrap(options[:dependencies])
+        cache_key = ([name, details_key, format] + dependencies).join('.')
+
         # this is a correctly done double-checked locking idiom
         # (ThreadSafe::Cache's lookups have volatile semantics)
         @@cache[cache_key] || @@digest_monitor.synchronize do

actionview/test/template/digestor_test.rb

@@ -15,6 +15,16 @@ def initialize(template_path)
 class FixtureFinder
   FIXTURES_DIR = "#{File.dirname(__FILE__)}/../fixtures/digestor"
 
+  attr_reader :details
+
+  def initialize
+    @details = {}
+  end
+
+  def details_key
+    details.hash
+  end
+
   def find(logical_name, keys, partial, options)
     FixtureTemplate.new("digestor/#{partial ? logical_name.gsub(%r|/([^/]+)$|, '/_\1') : logical_name}.#{options[:formats].first}.erb")
   end
@@ -140,6 +150,20 @@ def test_collection_derived_from_record_dependency
     end
   end
 
+  def test_details_are_included_in_cache_key
+    # Cache the template digest.
+    old_digest = digest("events/_event")
+
+    # Change the template; the cached digest remains unchanged.
+    change_template("events/_event")
+
+    # The details are changed, so a new cache key is generated.
+    finder.details[:foo] = "bar"
+
+    # The cache is busted.
+    assert_not_equal old_digest, digest("events/_event")
+  end
+
   def test_extra_whitespace_in_render_partial
     assert_digest_difference("messages/edit") do
       change_template("messages/_form")
@@ -220,7 +244,11 @@ def assert_digest_difference(template_name, persistent = false)
     end
 
     def digest(template_name, options={})
-      ActionView::Digestor.digest(template_name, :html, FixtureFinder.new, options)
+      ActionView::Digestor.digest(template_name, :html, finder, options)
+    end
+
+    def finder
+      @finder ||= FixtureFinder.new
     end
 
     def change_template(template_name)