symfony
diff --git a/‎src/Symfony/Component/HttpKernel/HttpCache/HttpCache.php
Copy file name to clipboardExpand all lines: src/Symfony/Component/HttpKernel/HttpCache/HttpCache.php
+13-1Lines changed: 13 additions & 1 deletion b/‎src/Symfony/Component/HttpKernel/HttpCache/HttpCache.php
Copy file name to clipboardExpand all lines: src/Symfony/Component/HttpKernel/HttpCache/HttpCache.php
+13-1Lines changed: 13 additions & 1 deletion
diff --git a/‎src/Symfony/Component/HttpKernel/Tests/HttpCache/HttpCacheTest.php
Copy file name to clipboardExpand all lines: src/Symfony/Component/HttpKernel/Tests/HttpCache/HttpCacheTest.php
+29Lines changed: 29 additions & 0 deletions b/‎src/Symfony/Component/HttpKernel/Tests/HttpCache/HttpCacheTest.php
Copy file name to clipboardExpand all lines: src/Symfony/Component/HttpKernel/Tests/HttpCache/HttpCacheTest.php
+29Lines changed: 29 additions & 0 deletions
@@ -69,6 +69,17 @@ class HttpCache implements HttpKernelInterface, TerminableInterface
      *                            the cache can serve a stale response when an error is encountered (default: 60).
      *                            This setting is overridden by the stale-if-error HTTP Cache-Control extension
      *                            (see RFC 5861).
+     *
+     *  * strict_smaxage          RFC 7234 Section 5.2.2.9 (https://tools.ietf.org/html/rfc7234#section-5.2.2.9)
+     *                            mandates that `s-maxage` implies `proxy-revalidate`. This means that when `s-maxage`
+     *                            is present on a Response, it must not be served stale. This prohibits the `stale-if-error`
+     *                            behavior for such responses, greatly reducing the benefit of that feature.
+     *                            Since Symfony for a long time encouraged the use of `s-maxage` and treated it like a
+     *                            short form of `public, maxage=...` (without obeying this RFC peculiarity), this configuration
+     *                            switch can be used to ignore these extra semantics.
+     *                            When set to `false` (the default value), responses with `s-maxage` _may_ be served stale
+     *                            when the backend returns an 5xx error on revalidation. Set this to `true` for strict
+     *                            compliance with Sections 5.2.2.9 and 4.2.4 of RFC 7234.
      */
     public function __construct(HttpKernelInterface $kernel, StoreInterface $store, SurrogateInterface $surrogate = null, array $options = [])
     {
@@ -87,6 +98,7 @@ public function __construct(HttpKernelInterface $kernel, StoreInterface $store,
             'allow_revalidate' => false,
             'stale_while_revalidate' => 2,
             'stale_if_error' => 60,
+            'strict_smaxage' => false,
         ], $options);
     }
 
@@ -469,7 +481,7 @@ protected function forward(Request $request, $catch = false, Response $entry = n
             && \in_array($response->getStatusCode(), [500, 502, 503, 504])
             && !$entry->headers->hasCacheControlDirective('no-cache')
             && !$entry->mustRevalidate()
-            && !$entry->headers->hasCacheControlDirective('s-maxage')
+            && (!$this->options['strict_smaxage'] || !$entry->headers->hasCacheControlDirective('s-maxage'))
         ) {
             if (null === $age = $entry->headers->getCacheControlDirective('stale-if-error')) {
                 $age = $this->options['stale_if_error'];
 
@@ -1627,6 +1627,7 @@ public function testResponsesThatMustNotBeUsedStaleIfError($responseHeaders, $sl
 
         $this->setNextResponses($responses);
         $this->cacheConfig['stale_if_error'] = 10; // after stale, may be served for 10s
+        $this->cacheConfig['strict_smaxage'] = true; // full RFC compliance for this feature
 
         $this->request('GET', '/'); // warm cache
 
@@ -1656,6 +1657,34 @@ public function getResponseDataThatMustNotBeServedStaleIfError()
         yield 'must-revalidate requires positive validation once stale' => [['Cache-Control' => 'public, max-age=10, must-revalidate'], 15];
         yield 'proxy-revalidate requires positive validation once stale' => [['Cache-Control' => 'public, max-age=10, proxy-revalidate'], 15];
     }
+
+    public function testStaleIfErrorWhenStrictSmaxageDisabled()
+    {
+        $responses = [
+            [
+                'status' => 200,
+                'body' => 'OK',
+                'headers' => ['Cache-Control' => 'public, s-maxage=20'],
+            ],
+            [
+                'status' => 500,
+                'body' => 'FAIL',
+                'headers' => [],
+            ],
+        ];
+
+        $this->setNextResponses($responses);
+        $this->cacheConfig['stale_if_error'] = 10;
+        $this->cacheConfig['strict_smaxage'] = false;
+
+        $this->request('GET', '/'); // warm cache
+        sleep(25);
+        $this->request('GET', '/'); // hit backend error
+
+        $this->assertEquals(200, $this->response->getStatusCode());
+        $this->assertEquals('OK', $this->response->getContent());
+        $this->assertTraceContains('stale-if-error');
+    }
 }
 
 class TestKernel implements HttpKernelInterface