SimpleCacheBridge::setMultiple() not compatible with NamespacedCachePool?

[beporter]

I've encountered an issue trying to combine a NamespacedCachePool with the SimpleCacheBridge.

Environment:

$ php --version
PHP 7.2.12-1+ubuntu16.04.1+deb.sury.org+1 (cli) (built: Nov 12 2018 09:55:12) ( NTS )
Copyright (c) 1997-2018 The PHP Group
Zend Engine v3.2.0, Copyright (c) 1998-2018 Zend Technologies
    with Zend OPcache v7.2.12-1+ubuntu16.04.1+deb.sury.org+1, Copyright (c) 1999-2018, by Zend Technologies
    with Xdebug v2.6.1, Copyright (c) 2002-2018, by Derick Rethans

$ composer info
cache/cache                           1.0.0   Library of all the php-cache adapters
cache/simple-cache-bridge             1.0.0   A PSR-6 bridge to PSR-16. This will make any PSR-6 cache compatible with SimpleCache.
psr/cache                             1.0.1   Common interface for caching libraries
psr/simple-cache                      1.0.1   Common interfaces for simple caching
# **snip**

Example php file to reproduce:

#!/usr/bin/env php
<?php
require 'vendor/autoload.php';

use Cache\Adapter\PHPArray\ArrayCachePool;
use Cache\Bridge\SimpleCache\SimpleCacheBridge;
use Cache\Namespaced\NamespacedCachePool;

$pool = new SimpleCacheBridge(
    new NamespacedCachePool(
        new ArrayCachePool(),
        'my_prefix'
    )
);

$pool->setMultiple([
    'key1' => 'val1',
    'key2' => 'val2',
]);

Error:

$ php cachetest.php
PHP Notice:  Undefined index: |my_prefix|key1 in ./vendor/cache/simple-cache-bridge/SimpleCacheBridge.php on line 177
PHP Stack trace:
PHP   1. {main}() ./cachetest.php:0
PHP   2. Cache\Bridge\SimpleCache\SimpleCacheBridge->setMultiple() ./cachetest.php:17

The issue seems to be here:

        $items = $this->cacheItemPool->getItems($keys);

        // **snip**

        foreach ($items as $key => $item) {
            /* @var $item CacheItemInterface */
            $item->set($arrayValues[$key]);
            // ...

In $arrayValues[$key], the $key being used includes the prefix that was auto-added by NamespacedCachePool:: prefixValue($key), but $arrayValues is provided by the end user and is therefore not prefixed yet (nor should it be.) One possible fix might be to somehow strip the prefix (if present) from $key before attempting to access $arrayValues[$key].

[beporter]

As a related question: Why does NamespacedCachePool::getItems(...) not strip the prefix from the indices of the values it returns? For example:

$pool = new NamespacedCachePool(
    new ArrayCachePool(),
    'my_prefix'
);

$data = [
    'key1' => 'val1',
    'key2' => 'val2',
];

foreach ($data as $key =>$val) {
    $item = $pool->getItem($key);
    $item->set($val);
    $pool->save($item);
}

$identityTest = $pool->getItems(array_keys($data));

// Expected: $identityTest === $data
// Actual: $identityTest !== $data  (Keys in $identityTest contain `|my_prefix|` whereas keys in $data do not.)

Correcting this could be another possible fix for the current issue, but seems like much more of a breaking change.

[beporter]

As a workaround (and in case it helps anyone else), I managed to override the NamespacedCachePool to remove the prefix from the indices returned from ::getItems().

<?php
/**
 * Fixes https://github.com/php-cache/issues/issues/139
 *
 * @TODO: Remove this class when php-cache/issues#139 is fixed.
 */

namespace App\Lib;

use Cache\Hierarchy\HierarchicalPoolInterface;
use Cache\Namespaced\NamespacedCachePool as NamespacedCachePoolOrig;
use \Traversable;

/**
 * \App\Lib\NamespacedCachePool
 */
class NamespacedCachePool extends NamespacedCachePoolOrig
{
    /**
     * Store the calculated prefix string.
     *
     * @var string
     */
    protected $prefix;

    /**
     * Have to override the constructor to get access to $namespace because
     * ::$namespace and ::prefixValue() are both declared as `private` in
     * the parent class.
     *
     * @param HierarchicalPoolInterface $cachePool
     * @param string                    $namespace
     */
    public function __construct(HierarchicalPoolInterface $cachePool, $namespace)
    {
        parent::__construct($cachePool, $namespace);

        $this->prefix = HierarchicalPoolInterface::HIERARCHY_SEPARATOR
            . $namespace
            . HierarchicalPoolInterface::HIERARCHY_SEPARATOR;
    }

    /**
     * Overrides the normal ::getItems() to properly strip the namespace prefix
     * from the returned indices.
     *
     * @param array $keys
     * @return array Sets of [un-prefixed-keys => values].
     */
    public function getItems(array $keys = [])
    {
        return iterator_to_array($this->yieldWithoutPrefix(parent::getItems($keys)));
    }

    /**
     * Generator that does the work of stripping the namespace prefix from keys in $items.
     *
     * @param array|\Traversable $items The results returned from the underlying cache store.
     * @return array Same results with key names stripped of the namespace prefix.
     */
    protected function yieldWithoutPrefix($items)
    {
        foreach ($items as $key => $val) {
            yield str_replace($this->prefix, '', $key) => $val;
        }
    }
}