move digest cache on to the DetailsKey object

This moves digest calculation cache on to the details key object.
Before, the digest cache was a class level ivar, and one of the keys was
the hash value of the details key object:

  https://github.com/rails/rails/blob/13c4cc3b5aea02716b7459c0da641438077f5236/actionview/lib/action_view/digestor.rb#L28

An object's hash value is not unique, so it's possible for this cache
key to produce colliding keys with no resolution.  This commit move
cache on to the details key object itself, so we know that the digests
are always unique per details key object.

1 files changed, 2 insertions, 3 deletions

diff --git a/actionview/test/template/digestor_test.rb b/actionview/test/template/digestor_test.rb
index e50caac6d8..9ff5f7126b 100644
--- a/actionview/test/template/digestor_test.rb
+++ b/actionview/test/template/digestor_test.rb
@@ -33,7 +33,6 @@ class TemplateDigestorTest < ActionView::TestCase
   def teardown
     Dir.chdir @cwd
     FileUtils.rm_r @tmp_dir
-    ActionView::Digestor.cache.clear
   end
 
   def test_top_level_change_reflected
@@ -301,12 +300,12 @@ class TemplateDigestorTest < ActionView::TestCase
 
     def assert_digest_difference(template_name, options = {})
       previous_digest = digest(template_name, options)
-      ActionView::Digestor.cache.clear
+      finder.digest_cache.clear
 
       yield
 
       assert_not_equal previous_digest, digest(template_name, options), "digest didn't change"
-      ActionView::Digestor.cache.clear
+      finder.digest_cache.clear
     end
 
     def digest(template_name, options = {})