bug symfony#25822 [Cache] Fix handling of apcu_fetch() edgy behavior (nicolas-grekas)

This PR was merged into the 3.3 branch.

Discussion
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[Cache] Fix handling of apcu_fetch() edgy behavior

| Q             | A
| ------------- | ---
| Branch?       | 3.3
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Replaces symfony#25819. Cannot be tested as I don't know how to trigger this behavior.

Commits
-------

c707c4c [Cache] Fix handling of apcu_fetch() edgy behavior

Author: fabpot

src/Symfony/Component/Cache/Tests/Adapter/ApcuAdapterTest.php

@@ -29,7 +29,7 @@ public function createCachePool($defaultLifetime = 0)
         }
         if ('cli' === PHP_SAPI && !ini_get('apc.enable_cli')) {
             if ('testWithCliSapi' !== $this->getName()) {
-                $this->markTestSkipped('APCu extension is required.');
+                $this->markTestSkipped('apc.enable_cli=1 is required.');
             }
         }
         if ('\\' === DIRECTORY_SEPARATOR) {

src/Symfony/Component/Cache/Traits/ApcuTrait.php

@@ -52,7 +52,11 @@ private function init($namespace, $defaultLifetime, $version)
     protected function doFetch(array $ids)
     {
         try {
-            return apcu_fetch($ids) ?: array();
+            foreach (apcu_fetch($ids, $ok) ?: array() as $k => $v) {
+                if (null !== $v || $ok) {
+                    yield $k => $v;
+                }
+            }
         } catch (\Error $e) {
             throw new \ErrorException($e->getMessage(), $e->getCode(), E_ERROR, $e->getFile(), $e->getLine());
         }