Fast forward resolved/rejected promises with await

WyriHaximus · WyriHaximus · commit b67fea3f90bb · 2022-01-10T08:44:51.000+01:00
This makes `await`ing an already resolved promise significantly faster. Ported from: #18
diff --git a/src/functions.php b/src/functions.php
@@ -53,24 +53,41 @@
 function await(PromiseInterface $promise)
 {
     $wait = true;
-    $resolved = null;
-    $exception = null;
+    $resolved = false;
     $rejected = false;
+    $resolvedValue = null;
+    $rejectedThrowable = null;
 
     $promise->then(
-        function ($c) use (&$resolved, &$wait) {
-            $resolved = $c;
+        function ($c) use (&$resolved, &$resolvedValue, &$wait) {
+            $resolvedValue = $c;
+            $resolved = true;
             $wait = false;
             Loop::stop();
         },
-        function ($error) use (&$exception, &$rejected, &$wait) {
-            $exception = $error;
+        function ($error) use (&$rejected, &$rejectedThrowable, &$wait) {
+            // promise is rejected with an unexpected value (Promise API v1 or v2 only)
+            if (!$error instanceof \Exception && !$error instanceof \Throwable) {
+                $error = new \UnexpectedValueException(
+                    'Promise rejected with unexpected value of type ' . (is_object($error) ? get_class($error) : gettype($error))
+                );
+            }
+
+            $rejectedThrowable = $error;
             $rejected = true;
             $wait = false;
             Loop::stop();
         }
     );
 
+    if ($rejected) {
+        throw $rejectedThrowable;
+    }
+
+    if ($resolved) {
+        return $resolvedValue;
+    }
+
     // Explicitly overwrite argument with null value. This ensure that this
     // argument does not show up in the stack trace in PHP 7+ only.
     $promise = null;
@@ -80,17 +97,10 @@ function ($error) use (&$exception, &$rejected, &$wait) {
     }
 
     if ($rejected) {
-        // promise is rejected with an unexpected value (Promise API v1 or v2 only)
-        if (!$exception instanceof \Throwable) {
-            $exception = new \UnexpectedValueException(
-                'Promise rejected with unexpected value of type ' . (is_object($exception) ? get_class($exception) : gettype($exception))
-            );
-        }
-
-        throw $exception;
+        throw $rejectedThrowable;
     }
 
-    return $resolved;
+    return $resolvedValue;
 }
 
 
diff --git a/tests/AwaitTest.php b/tests/AwaitTest.php
@@ -122,6 +122,13 @@ public function testAwaitShouldNotCreateAnyGarbageReferencesForRejectedPromise()
         $this->assertEquals(0, gc_collect_cycles());
     }
 
+    public function testAlreadyFulfilledPromiseShouldNotSuspendFiber()
+    {
+        for ($i = 0; $i < 6; $i++) {
+            $this->assertSame($i, React\Async\await(React\Promise\resolve($i)));
+        }
+    }
+
     public function testAwaitShouldNotCreateAnyGarbageReferencesForPromiseRejectedWithNullValue()
     {
         if (!interface_exists('React\Promise\CancellablePromiseInterface')) {

Original file line number	Diff line number	Diff line change
`@@ -122,6 +122,13 @@ public function testAwaitShouldNotCreateAnyGarbageReferencesForRejectedPromise()`
`122`	`122`	`$this->assertEquals(0, gc_collect_cycles());`
`123`	`123`	`}`
`124`	`124`
	`125`	`+ public function testAlreadyFulfilledPromiseShouldNotSuspendFiber()`
	`126`	`+ {`
	`127`	`+ for ($i = 0; $i < 6; $i++) {`
	`128`	`+ $this->assertSame($i, React\Async\await(React\Promise\resolve($i)));`
	`129`	`+ }`
	`130`	`+ }`
	`131`	`+`
`125`	`132`	`public function testAwaitShouldNotCreateAnyGarbageReferencesForPromiseRejectedWithNullValue()`
`126`	`133`	`{`
`127`	`134`	`if (!interface_exists('React\Promise\CancellablePromiseInterface')) {`