remove excessive cache key generator calls

Author: modethirteen

src/CacheBuilder.php

@@ -65,6 +65,11 @@ class CacheBuilder implements ICacheBuilder {
      */
     private $dispatcher = null;
 
+    /**
+     * @var bool
+     */
+    private $isCacheKeyStale = true;
+
     /**
      * @var Closure
      */
@@ -131,7 +136,7 @@ public function get() {
 
             // the cache key used for setting a value may be different than the key used to get a value if upstream
             // ...dependencies and state have changed - to be safe, we regenerate the key
-            $this->cacheKey = null;
+            $this->isCacheKeyStale = true;
             $key = $this->getCacheKey();
             if($this->getCache() !== null && $key !== null) {
                 $cacheLifespanBuilder = $this->cacheLifespanBuilder;
@@ -157,9 +162,10 @@ public function getCache() : ?CacheInterface {
     }
 
     public function getCacheKey() : ?string {
-        if($this->cacheKey === null) {
+        if($this->isCacheKeyStale) {
             $cacheKeyBuilder = $this->cacheKeyBuilder;
             $this->cacheKey = $cacheKeyBuilder();
+            $this->isCacheKeyStale = false;
         }
         return $this->cacheKey;
     }

tests/CacheBuilder_Test.php

@@ -412,14 +412,16 @@ public function Cache_hit_fails_validation_with_build_and_updated_cache_key(bool
                 [static::equalTo((new Event('cache:set.success'))->withCache($cache, 'bar'))]
             );
         $key = 'foo';
+        $counter = 0;
 
         // act
         $builder = (new CacheBuilder())
             ->withBuilder(function() use (&$key) : string {
                 $key = 'bar';
                 return 'xyzzy';
             })
-            ->withCache($cache, function() use (&$key) : string {
+            ->withCache($cache, function() use (&$key, &$counter) : string {
+                $counter++;
                 return $key;
             })
             ->withCacheValidator(function($result) : bool {
@@ -439,6 +441,7 @@ public function Cache_hit_fails_validation_with_build_and_updated_cache_key(bool
 
         // assert
         static::assertEquals('xyzzy', $result);
+        static::assertEquals(2, $counter);
     }
 
     /**