Merge pull request rails#52289 from Shopify/fix-strict-freshness

Check `If-None-Match` before `If-Modified-Since` with strict freshness

Author: byroot

actionpack/lib/action_dispatch/http/cache.rb

@@ -44,9 +44,9 @@ def etag_matches?(etag)
         # Reference: http://tools.ietf.org/html/rfc7232#section-6
         def fresh?(response)
           if Request.strict_freshness
-            if if_modified_since
+            if if_none_match
               etag_matches?(response.etag)
-            elsif if_none_match
+            elsif if_modified_since
               not_modified?(response.last_modified)
             else
               false

actionpack/test/controller/api/conditional_get_test.rb

@@ -70,7 +70,25 @@ def test_etag_matches
     assert_response :not_modified
   end
 
-  def test_etag_precedence_over_last_modified
+  def test_strict_freshness_with_etag
+    with_strict_freshness(true) do
+      @request.if_none_match = weak_etag([:foo, 123])
+
+      get :one
+      assert_response :not_modified
+    end
+  end
+
+  def test_strict_freshness_with_last_modified
+    with_strict_freshness(true) do
+      @request.if_modified_since = @last_modified
+
+      get :one
+      assert_response :not_modified
+    end
+  end
+
+  def test_strict_freshness_etag_precedence_over_last_modified
     with_strict_freshness(true) do
       # Not modified because the etag matches
       @request.if_modified_since = 5.years.ago.httpdate