bug #32025 SimpleCacheAdapter fails to cache any item if a namespace is used (moufmouf)

This PR was squashed before being merged into the 3.4 branch (closes #32025).

Discussion
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SimpleCacheAdapter fails to cache any item if a namespace is used

| Q             | A
| ------------- | ---
| Branch?       |3.4
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT

This is a backport of #32019

The SimpleCacheAdapter extends AdapterTestCase.
When adding a namespace, the AdapterTestCase adds ":" after the namespace:

https://github.com/symfony/symfony/blob/v4.3.1/src/Symfony/Component/Cache/Adapter/AbstractAdapter.php#L37

The namespace is prepended to the cache key.
But in PSR-16, the ":" is a forbidden character.

As a result, the cache key is invalid and cache is not persisted. If you use Psr16Adapter + a namespace, the cache simply does not work.

As per @nicolas-grekas advices, a NS_SEPARATOR const is added to change the namespace separator for the `SimpleCacheAdapter` to "_" (that is compatible with PSR-16).

The first commit of this PR starts with an additional test and no fix (to showcase the problem).

Commits
-------

ffd3469ddf SimpleCacheAdapter fails to cache any item if a namespace is used

src/Symfony/Component/Cache/Adapter/AbstractAdapter.php

@@ -39,7 +39,7 @@ abstract class AbstractAdapter implements AdapterInterface, LoggerAwareInterface
      */
     protected function __construct($namespace = '', $defaultLifetime = 0)
     {
-        $this->namespace = '' === $namespace ? '' : CacheItem::validateKey($namespace).':';
+        $this->namespace = '' === $namespace ? '' : CacheItem::validateKey($namespace).static::getNsSeparator();
         if (null !== $this->maxIdLength && \strlen($namespace) > $this->maxIdLength - 24) {
             throw new InvalidArgumentException(sprintf('Namespace must be %d chars max, %d given ("%s")', $this->maxIdLength - 24, \strlen($namespace), $namespace));
         }

src/Symfony/Component/Cache/Adapter/SimpleCacheAdapter.php

@@ -75,4 +75,12 @@ class SimpleCacheAdapter extends AbstractAdapter implements PruneableInterface
     {
         return $this->pool->setMultiple($values, 0 === $lifetime ? null : $lifetime);
     }
+
+    /**
+     * @return string the namespace separator for cache keys
+     */
+    protected static function getNsSeparator()
+    {
+        return '_';
+    }
 }

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

@@ -12,6 +12,7 @@
 namespace Symfony\Component\Cache\Tests\Adapter;
 
 use Symfony\Component\Cache\Adapter\SimpleCacheAdapter;
+use Symfony\Component\Cache\Simple\ArrayCache;
 use Symfony\Component\Cache\Simple\FilesystemCache;
 
 /**
@@ -27,4 +28,14 @@ class SimpleCacheAdapterTest extends AdapterTestCase
     {
         return new SimpleCacheAdapter(new FilesystemCache(), '', $defaultLifetime);
     }
+
+    public function testValidCacheKeyWithNamespace()
+    {
+        $cache = new SimpleCacheAdapter(new ArrayCache(), 'some_namespace', 0);
+        $item = $cache->getItem('my_key');
+        $item->set('someValue');
+        $cache->save($item);
+
+        $this->assertTrue($cache->getItem('my_key')->isHit(), 'Stored item is successfully retrieved.');
+    }
 }

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

@@ -106,7 +106,7 @@ trait AbstractTrait
     {
         $this->deferred = [];
         if ($cleared = $this->versioningIsEnabled) {
-            $namespaceVersion = substr_replace(base64_encode(pack('V', mt_rand())), ':', 5);
+            $namespaceVersion = substr_replace(base64_encode(pack('V', mt_rand())), static::getNsSeparator(), 5);
             try {
                 $cleared = $this->doSave(['@'.$this->namespace => $namespaceVersion], 0);
             } catch (\Exception $e) {
@@ -235,13 +235,13 @@ trait AbstractTrait
         CacheItem::validateKey($key);
 
         if ($this->versioningIsEnabled && '' === $this->namespaceVersion) {
-            $this->namespaceVersion = '1:';
+            $this->namespaceVersion = '1'.static::getNsSeparator();
             try {
                 foreach ($this->doFetch(['@'.$this->namespace]) as $v) {
                     $this->namespaceVersion = $v;
                 }
-                if ('1:' === $this->namespaceVersion) {
-                    $this->namespaceVersion = substr_replace(base64_encode(pack('V', time())), ':', 5);
+                if ('1'.static::getNsSeparator() === $this->namespaceVersion) {
+                    $this->namespaceVersion = substr_replace(base64_encode(pack('V', time())), static::getNsSeparator(), 5);
                     $this->doSave(['@'.$this->namespace => $this->namespaceVersion], 0);
                 }
             } catch (\Exception $e) {
@@ -252,7 +252,7 @@ trait AbstractTrait
             return $this->namespace.$this->namespaceVersion.$key;
         }
         if (\strlen($id = $this->namespace.$this->namespaceVersion.$key) > $this->maxIdLength) {
-            $id = $this->namespace.$this->namespaceVersion.substr_replace(base64_encode(hash('sha256', $key, true)), ':', -(\strlen($this->namespaceVersion) + 22));
+            $id = $this->namespace.$this->namespaceVersion.substr_replace(base64_encode(hash('sha256', $key, true)), static::getNsSeparator(), -(\strlen($this->namespaceVersion) + 22));
         }
 
         return $id;
@@ -265,4 +265,12 @@ trait AbstractTrait
     {
         throw new \DomainException('Class not found: '.$class);
     }
+
+    /**
+     * @return string the namespace separator for cache keys
+     */
+    protected static function getNsSeparator()
+    {
+        return ':';
+    }
 }