#5 If "no-cache" stale the cache entry

src/AbstractPrivateCache.php

@@ -28,6 +28,12 @@ protected function getCacheObject(ResponseInterface $response)
                 return null;
             }
 
+            if (in_array("no-cache", $cacheControlDirectives)) {
+                // Stale response (RFC 7234 5.2.1.4)
+                $entry = new CacheEntry($response, new \DateTime('-1 seconds'));
+                return $entry->hasValidationInformation() ? $entry : null;
+            }
+
             foreach ($cacheControlDirectives as $directive) {
                 $matches = [];
 

src/CacheEntry.php

@@ -99,4 +99,12 @@ public function serveStaleIfError()
         return (bool)$this->staleIfError;
     }
 
+    /**
+     * @return bool
+     */
+    public function hasValidationInformation()
+    {
+        return $this->response->hasHeader("Etag") || $this->response->hasHeader("Last-Modified");
+    }
+
 }

tests/HeaderCacheControlTest.php

@@ -35,6 +35,16 @@ public function setUp()
                         (new Response())
                             ->withAddedHeader("Cache-Control", "no-store")
                     );
+                case '/no-cache':
+                    if ($request->getHeaderLine("If-None-Match") == "TheHash") {
+                        return new FulfilledPromise(new Response(304));
+                    }
+
+                    return new FulfilledPromise(
+                        (new Response())
+                            ->withAddedHeader("Cache-Control", "no-cache")
+                            ->withAddedHeader("Etag", "TheHash")
+                    );
             }
 
             throw new \InvalidArgumentException();
@@ -68,4 +78,12 @@ public function testNoStoreHeader()
         $this->assertEquals("", $response->getHeaderLine("X-Cache"));
     }
 
+    public function testNoCacheHeader()
+    {
+        $this->client->get("http://test.com/no-cache");
+
+        $response = $this->client->get("http://test.com/no-cache");
+        $this->assertEquals("HIT with validation", $response->getHeaderLine("X-Cache"));
+    }
+
 }