bug #40545 [HttpFoundation] Fix isNotModified determination logic (ol0lll)

This PR was squashed before being merged into the 4.4 branch.

Discussion
----------

[HttpFoundation] Fix isNotModified determination logic

| Q             | A
| ------------- | ---
| Branch?       | 4.4  <!-- see below -->
| Bug fix?      | yes
| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->
| Deprecations? | no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tickets       | Fix #37948 <!-- prefix each issue number with "Fix #", no need to create an issue if none exist, explain below instead -->
| License       | MIT
| Doc PR        | symfony/symfony-docs#... <!-- required for new features -->

Use weak comparison for etags; Only do if-modified-since when no if-none-match header is present.
See symfony/symfony#37948 (comment)

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Commits
-------

77bd21adfc [HttpFoundation] Fix isNotModified determination logic

Author: fabpot

Request.php

@@ -1564,7 +1564,7 @@ public function getContent($asResource = false)
      */
     public function getETags()
     {
-        return preg_split('/\s*,\s*/', $this->headers->get('if_none_match', ''), -1, \PREG_SPLIT_NO_EMPTY);
+        return preg_split('/\s*,\s*/', $this->headers->get('If-None-Match', ''), -1, \PREG_SPLIT_NO_EMPTY);
     }
 
     /**

Response.php

@@ -1079,12 +1079,27 @@ public function isNotModified(Request $request): bool
         $lastModified = $this->headers->get('Last-Modified');
         $modifiedSince = $request->headers->get('If-Modified-Since');
 
-        if ($etags = $request->getETags()) {
-            $notModified = \in_array($this->getEtag(), $etags) || \in_array('*', $etags);
-        }
+        if ($ifNoneMatchEtags = $request->getETags()) {
+            $etag = $this->getEtag();
+            if (0 == strncmp($etag, 'W/', 2)) {
+                $etag = substr($etag, 2);
+            }
+
+            // Use weak comparison as per https://tools.ietf.org/html/rfc7232#section-3.2.
+            foreach ($ifNoneMatchEtags as $ifNoneMatchEtag) {
+                if (0 == strncmp($ifNoneMatchEtag, 'W/', 2)) {
+                    $ifNoneMatchEtag = substr($ifNoneMatchEtag, 2);
+                }
 
-        if ($modifiedSince && $lastModified) {
-            $notModified = strtotime($modifiedSince) >= strtotime($lastModified) && (!$etags || $notModified);
+                if ($ifNoneMatchEtag === $etag || '*' === $ifNoneMatchEtag) {
+                    $notModified = true;
+                    break;
+                }
+            }
+        }
+        // Only do If-Modified-Since date comparison when If-None-Match is not present as per https://tools.ietf.org/html/rfc7232#section-3.3.
+        elseif ($modifiedSince && $lastModified) {
+            $notModified = strtotime($modifiedSince) >= strtotime($lastModified);
         }
 
         if ($notModified) {

Tests/ResponseTest.php

@@ -194,7 +194,7 @@ public function testIsNotModifiedEtag()
         $etagTwo = 'randomly_generated_etag_2';
 
         $request = new Request();
-        $request->headers->set('if_none_match', sprintf('%s, %s, %s', $etagOne, $etagTwo, 'etagThree'));
+        $request->headers->set('If-None-Match', sprintf('%s, %s, %s', $etagOne, $etagTwo, 'etagThree'));
 
         $response = new Response();
 
@@ -206,6 +206,38 @@ public function testIsNotModifiedEtag()
 
         $response->headers->set('ETag', '');
         $this->assertFalse($response->isNotModified($request));
+
+        // Test wildcard
+        $request = new Request();
+        $request->headers->set('If-None-Match', '*');
+
+        $response->headers->set('ETag', $etagOne);
+        $this->assertTrue($response->isNotModified($request));
+    }
+
+    public function testIsNotModifiedWeakEtag()
+    {
+        $etag = 'randomly_generated_etag';
+        $weakEtag = 'W/randomly_generated_etag';
+
+        $request = new Request();
+        $request->headers->set('If-None-Match', $etag);
+        $response = new Response();
+
+        $response->headers->set('ETag', $etag);
+        $this->assertTrue($response->isNotModified($request));
+
+        $response->headers->set('ETag', $weakEtag);
+        $this->assertTrue($response->isNotModified($request));
+
+        $request->headers->set('If-None-Match', $weakEtag);
+        $response = new Response();
+
+        $response->headers->set('ETag', $etag);
+        $this->assertTrue($response->isNotModified($request));
+
+        $response->headers->set('ETag', $weakEtag);
+        $this->assertTrue($response->isNotModified($request));
     }
 
     public function testIsNotModifiedLastModifiedAndEtag()
@@ -216,14 +248,14 @@ public function testIsNotModifiedLastModifiedAndEtag()
         $etag = 'randomly_generated_etag';
 
         $request = new Request();
-        $request->headers->set('if_none_match', sprintf('%s, %s', $etag, 'etagThree'));
+        $request->headers->set('If-None-Match', sprintf('%s, %s', $etag, 'etagThree'));
         $request->headers->set('If-Modified-Since', $modified);
 
         $response = new Response();
 
         $response->headers->set('ETag', $etag);
         $response->headers->set('Last-Modified', $after);
-        $this->assertFalse($response->isNotModified($request));
+        $this->assertTrue($response->isNotModified($request));
 
         $response->headers->set('ETag', 'non-existent-etag');
         $response->headers->set('Last-Modified', $before);
@@ -240,7 +272,7 @@ public function testIsNotModifiedIfModifiedSinceAndEtagWithoutLastModified()
         $etag = 'randomly_generated_etag';
 
         $request = new Request();
-        $request->headers->set('if_none_match', sprintf('%s, %s', $etag, 'etagThree'));
+        $request->headers->set('If-None-Match', sprintf('%s, %s', $etag, 'etagThree'));
         $request->headers->set('If-Modified-Since', $modified);
 
         $response = new Response();