add fail callback for DoubleCheckedLocking::then()

Author: mvorisek

src/Util/DoubleCheckedLocking.php

@@ -24,8 +24,7 @@ class DoubleCheckedLocking
     private $check;
 
     /**
-     * @param callable(): bool $check Callback that decides if the lock should be acquired and is rechecked
-     *                                after a lock has been acquired
+     * @param callable(): bool $check Decides if a lock should be acquired and is rechecked after the lock has been acquired
      */
     public function __construct(Mutex $mutex, callable $check)
     {
@@ -34,31 +33,36 @@ public function __construct(Mutex $mutex, callable $check)
     }
 
     /**
-     * Executes a block of code only after the check callback passes
-     * before and after acquiring a lock.
+     * Execute a block of code only after the check callback passes before and after acquiring a lock.
      *
-     * @template T
+     * @template TSuccess
+     * @template TFail
      *
-     * @param callable(): T $code
+     * @param callable(): TSuccess $successFx
+     * @param callable(): TFail $failFx
      *
-     * @return T|false False if check did not pass
+     * @return TSuccess|TFail|false False if check did not pass
      *
      * @throws \Throwable
      * @throws LockAcquireException
      * @throws LockReleaseException
      */
-    public function then(callable $code)
+    public function then(callable $successFx, callable $failFx = null)
     {
         if (!($this->check)()) {
-            return false;
+            return $failFx !== null
+                ? $failFx()
+                : false;
         }
 
-        return $this->mutex->synchronized(function () use ($code) {
+        return $this->mutex->synchronized(function () use ($successFx, $failFx) {
             if (!($this->check)()) {
-                return false;
+                return $failFx !== null
+                    ? $failFx()
+                    : false;
             }
 
-            return $code();
+            return $successFx();
         });
     }
 }

tests/Util/DoubleCheckedLockingTest.php

@@ -129,4 +129,50 @@ public function testCodeExecuted(): void
         self::assertSame(1, $executedCount);
         self::assertSame('foo', $result);
     }
+
+    public function testFailCodeExecutedBeforeLock(): void
+    {
+        $this->mutex->expects(self::never())
+            ->method('synchronized');
+
+        $checkedLocking = new DoubleCheckedLocking($this->mutex, static function () {
+            return false;
+        });
+
+        $executedCount = 0;
+        $result = $checkedLocking->then(static function () {
+            self::fail();
+        }, static function () use (&$executedCount) {
+            ++$executedCount;
+
+            return 'foo';
+        });
+
+        self::assertSame(1, $executedCount);
+        self::assertSame('foo', $result);
+    }
+
+    public function testFailCodeExecutedAfterLock(): void
+    {
+        $this->mutex->expects(self::once())
+            ->method('synchronized')
+            ->willReturnCallback(static fn (\Closure $block) => $block());
+
+        $i = 0;
+        $checkedLocking = new DoubleCheckedLocking($this->mutex, static function () use (&$i) {
+            return $i++ === 0;
+        });
+
+        $executedCount = 0;
+        $result = $checkedLocking->then(static function () {
+            self::fail();
+        }, static function () use (&$executedCount) {
+            ++$executedCount;
+
+            return 'foo';
+        });
+
+        self::assertSame(1, $executedCount);
+        self::assertSame('foo', $result);
+    }
 }