feature #20851 [Cache] Add CacheItem::getPreviousTags() (nicolas-grekas)

This PR was merged into the 3.3-dev branch.

Discussion
----------

[Cache] Add CacheItem::getPreviousTags()

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

As discussed in #19728

Commits
-------

da35466 [Cache] Add CacheItem::getPreviousTags()

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

@@ -25,6 +25,7 @@ class TagAwareAdapter implements TagAwareAdapterInterface
     private $itemsAdapter;
     private $deferred = array();
     private $createCacheItem;
+    private $setCacheItemTags;
     private $getTagsByKey;
     private $invalidateTags;
     private $tagsAdapter;
@@ -38,7 +39,6 @@ function ($key, $value, CacheItem $protoItem) {
                 $item = new CacheItem();
                 $item->key = $key;
                 $item->value = $value;
-                $item->isHit = false;
                 $item->defaultLifetime = $protoItem->defaultLifetime;
                 $item->expiry = $protoItem->expiry;
                 $item->innerItem = $protoItem->innerItem;
@@ -49,6 +49,26 @@ function ($key, $value, CacheItem $protoItem) {
             null,
             CacheItem::class
         );
+        $this->setCacheItemTags = \Closure::bind(
+            function (CacheItem $item, $key, array &$itemTags) {
+                if (!$item->isHit) {
+                    return $item;
+                }
+                if (isset($itemTags[$key])) {
+                    foreach ($itemTags[$key] as $tag => $version) {
+                        $item->prevTags[$tag] = $tag;
+                    }
+                    unset($itemTags[$key]);
+                } else {
+                    $item->value = null;
+                    $item->isHit = false;
+                }
+
+                return $item;
+            },
+            null,
+            CacheItem::class
+        );
         $this->getTagsByKey = \Closure::bind(
             function ($deferred) {
                 $tagsByKey = array();
@@ -256,12 +276,12 @@ public function __destruct()
 
     private function generateItems($items, array $tagKeys)
     {
-        $bufferedItems = $itemTags = $invalidKeys = array();
-        $f = $this->createCacheItem;
+        $bufferedItems = $itemTags = array();
+        $f = $this->setCacheItemTags;
 
         foreach ($items as $key => $item) {
             if (!$tagKeys) {
-                yield $key => isset($invalidKeys[self::TAGS_PREFIX.$key]) ? $f($key, null, $item) : $item;
+                yield $key => $f($item, self::TAGS_PREFIX.$key, $itemTags);
                 continue;
             }
             if (!isset($tagKeys[$key])) {
@@ -270,24 +290,23 @@ private function generateItems($items, array $tagKeys)
             }
 
             unset($tagKeys[$key]);
-            if ($tags = $item->get()) {
-                $itemTags[$key] = $tags;
-            }
+            $itemTags[$key] = $item->get() ?: array();
+
             if (!$tagKeys) {
                 $tagVersions = $this->getTagVersions($itemTags);
 
                 foreach ($itemTags as $key => $tags) {
                     foreach ($tags as $tag => $version) {
                         if ($tagVersions[$tag] !== $version) {
-                            $invalidKeys[$key] = true;
+                            unset($itemTags[$key]);
                             continue 2;
                         }
                     }
                 }
-                $itemTags = $tagVersions = $tagKeys = null;
+                $tagVersions = $tagKeys = null;
 
                 foreach ($bufferedItems as $key => $item) {
-                    yield $key => isset($invalidKeys[self::TAGS_PREFIX.$key]) ? $f($key, null, $item) : $item;
+                    yield $key => $f($item, self::TAGS_PREFIX.$key, $itemTags);
                 }
                 $bufferedItems = null;
             }

src/Symfony/Component/Cache/CHANGELOG.md

@@ -4,6 +4,7 @@ CHANGELOG
 3.3.0
 -----
 
+ * [EXPERIMENTAL] added CacheItem::getPreviousTags() to get bound tags coming from the pool storage if any
  * added PSR-16 "Simple Cache" implementations for all existing PSR-6 adapters
  * added Psr6Cache and SimpleCacheAdapter for bidirectional interoperability between PSR-6 and PSR-16
  * added MemcachedAdapter (PSR-6) and MemcachedCache (PSR-16)

src/Symfony/Component/Cache/CacheItem.php

@@ -22,10 +22,11 @@ final class CacheItem implements CacheItemInterface
 {
     protected $key;
     protected $value;
-    protected $isHit;
+    protected $isHit = false;
     protected $expiry;
     protected $defaultLifetime;
     protected $tags = array();
+    protected $prevTags = array();
     protected $innerItem;
     protected $poolHash;
 
@@ -130,6 +131,18 @@ public function tag($tags)
         return $this;
     }
 
+    /**
+     * Returns the list of tags bound to the value coming from the pool storage if any.
+     *
+     * @return array
+     *
+     * @experimental in version 3.3
+     */
+    public function getPreviousTags()
+    {
+        return $this->prevTags;
+    }
+
     /**
      * Validates a cache key according to PSR-6.
      *

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

@@ -114,4 +114,15 @@ public function testTagItemExpiry()
 
         $this->assertFalse($pool->getItem('foo')->isHit());
     }
+
+    public function testGetPreviousTags()
+    {
+        $pool = $this->createCachePool();
+
+        $i = $pool->getItem('k');
+        $pool->save($i->tag('foo'));
+
+        $i = $pool->getItem('k');
+        $this->assertSame(array('foo' => 'foo'), $i->getPreviousTags());
+    }
 }