minor symfony#25176 [HttpKernel] Better handling of legacy cache (nicolas-grekas)

This PR was merged into the 3.4 branch.

Discussion
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[HttpKernel] Better handling of legacy cache

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | on
| Tests pass?   | yes
| Fixed tickets | symfony#25175
| License       | MIT
| Doc PR        | -

Even if this is edge case, it should improve DX when moving to 3.4 (I already experienced this issue myself :) )

Commits
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3a873f8 [HttpKernel] Better handling of legacy cache

Author: fabpot

src/Symfony/Component/HttpKernel/Kernel.php

@@ -581,8 +581,11 @@ protected function initializeContainer()
         $class = $this->getContainerClass();
         $cacheDir = $this->warmupDir ?: $this->getCacheDir();
         $cache = new ConfigCache($cacheDir.'/'.$class.'.php', $this->debug);
-        $fresh = true;
-        if (!$cache->isFresh()) {
+        if ($fresh = $cache->isFresh()) {
+            $this->container = require $cache->getPath();
+            $fresh = \is_object($this->container);
+        }
+        if (!$fresh) {
             if ($this->debug) {
                 $collectedLogs = array();
                 $previousHandler = set_error_handler(function ($type, $message, $file, $line) use (&$collectedLogs, &$previousHandler) {
@@ -632,11 +635,9 @@ protected function initializeContainer()
             $oldContainer = file_exists($cache->getPath()) && is_object($oldContainer = @include $cache->getPath()) ? new \ReflectionClass($oldContainer) : false;
 
             $this->dumpContainer($cache, $container, $class, $this->getContainerBaseClass());
-
-            $fresh = false;
+            $this->container = require $cache->getPath();
         }
 
-        $this->container = require $cache->getPath();
         $this->container->set('kernel', $this);
 
         if ($fresh) {