5 files changed, 9 insertions, 20 deletions
diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index abbadd404f..fccaeb5d32 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,7 +1,7 @@
-*   Introduced `ActiveSupport::Digest` that allows to specify hash function implementation
-    and defaults to `Digest::MD5`.
+*   Allow the hash function used to generate non-sensitive digests, such as the
+    ETag header, to be specified with `config.active_support.hash_digest_class`.
 
-    Replaced calls to `::Digest::MD5.hexdigest` with calls to `ActiveSupport::Digest.hexdigest`.
+    The object provided must respond to `#hexdigest`, e.g. `Digest::SHA1`.
 
     *Dmitri Dolguikh*
  
diff --git a/activesupport/lib/active_support/core_ext/module/delegation.rb b/activesupport/lib/active_support/core_ext/module/delegation.rb
index a77f903db5..4310df3024 100644
--- a/activesupport/lib/active_support/core_ext/module/delegation.rb
+++ b/activesupport/lib/active_support/core_ext/module/delegation.rb
@@ -115,11 +115,8 @@ class Module
   #   invoice.customer_address # => 'Vimmersvej 13'
   #
   # If the target is +nil+ and does not respond to the delegated method a
-  # +Module::DelegationError+ is raised, as with any other value. Sometimes,
-  # however, it makes sense to be robust to that situation and that is the
-  # purpose of the <tt>:allow_nil</tt> option: If the target is not +nil+, or it
-  # is and responds to the method, everything works as usual. But if it is +nil+
-  # and does not respond to the delegated method, +nil+ is returned.
+  # +Module::DelegationError+ is raised. If you wish to instead return +nil+,
+  # use the <tt>:allow_nil</tt> option.
   #
   #   class User < ActiveRecord::Base
   #     has_one :profile
diff --git a/activesupport/lib/active_support/digest.rb b/activesupport/lib/active_support/digest.rb
index d77eeb072b..fba10fbdcf 100644
--- a/activesupport/lib/active_support/digest.rb
+++ b/activesupport/lib/active_support/digest.rb
@@ -13,16 +13,8 @@ module ActiveSupport
       end
 
       def hexdigest(arg)
-        new.hexdigest(arg)
+        hash_digest_class.hexdigest(arg)[0...32]
       end
     end
-
-    def initialize(digest_class: nil)
-      @digest_class = digest_class || self.class.hash_digest_class
-    end
-
-    def hexdigest(arg)
-      @digest_class.hexdigest(arg).truncate(32)
-    end
   end
 end
diff --git a/activesupport/lib/active_support/railtie.rb b/activesupport/lib/active_support/railtie.rb
index 3488721df9..91872e29c8 100644
--- a/activesupport/lib/active_support/railtie.rb
+++ b/activesupport/lib/active_support/railtie.rb
@@ -68,9 +68,9 @@ module ActiveSupport
     end
 
     initializer "active_support.set_hash_digest_class" do |app|
-      if app.config.active_support.respond_to?(:use_hash_digest_class) && app.config.active_support.use_hash_digest_class
+      if app.config.active_support.respond_to?(:hash_digest_class) && app.config.active_support.hash_digest_class
         ActiveSupport::Digest.hash_digest_class =
-          app.config.active_support.use_hash_digest_class
+          app.config.active_support.hash_digest_class
       end
     end
   end
diff --git a/activesupport/test/digest_test.rb b/activesupport/test/digest_test.rb
index 5dec75b9fe..83ff2a8d83 100644
--- a/activesupport/test/digest_test.rb
+++ b/activesupport/test/digest_test.rb
@@ -16,7 +16,7 @@ class DigestTest < ActiveSupport::TestCase
     digest = ActiveSupport::Digest.hexdigest("hello friend")
 
     assert_equal 32, digest.length
-    assert_equal ::Digest::SHA1.hexdigest("hello friend").truncate(32), digest
+    assert_equal ::Digest::SHA1.hexdigest("hello friend")[0...32], digest
   ensure
     ActiveSupport::Digest.hash_digest_class = original_hash_digest_class
   end