Fix circular references when resolving with a promise which follows itself

Author: jsor

src/Promise.php

@@ -22,7 +22,7 @@ public function __construct(callable $resolver, callable $canceller = null)
     public function then(callable $onFulfilled = null, callable $onRejected = null, callable $onProgress = null)
     {
         if (null !== $this->result) {
-            return $this->result()->then($onFulfilled, $onRejected, $onProgress);
+            return $this->result->then($onFulfilled, $onRejected, $onProgress);
         }
 
         if (null === $this->canceller) {
@@ -43,7 +43,7 @@ public function then(callable $onFulfilled = null, callable $onRejected = null,
     public function done(callable $onFulfilled = null, callable $onRejected = null, callable $onProgress = null)
     {
         if (null !== $this->result) {
-            return $this->result()->done($onFulfilled, $onRejected, $onProgress);
+            return $this->result->done($onFulfilled, $onRejected, $onProgress);
         }
 
         $this->handlers[] = function (ExtendedPromiseInterface $promise) use ($onFulfilled, $onRejected) {
@@ -155,15 +155,7 @@ private function notify($update = null)
 
     private function settle(ExtendedPromiseInterface $promise)
     {
-        if ($promise instanceof LazyPromise) {
-            $promise = $promise->promise();
-        }
-
-        if ($promise === $this) {
-            $promise = new RejectedPromise(
-                new \LogicException('Cannot resolve a promise with itself.')
-            );
-        }
+        $promise = $this->unwrap($promise);
 
         $handlers = $this->handlers;
 
@@ -175,13 +167,30 @@ private function settle(ExtendedPromiseInterface $promise)
         }
     }
 
-    private function result()
+    private function unwrap($promise)
     {
-        while ($this->result instanceof self && null !== $this->result->result) {
-            $this->result = $this->result->result;
+        $promise = $this->extract($promise);
+
+        while ($promise instanceof self && null !== $promise->result) {
+            $promise = $this->extract($promise->result);
+        }
+
+        return $promise;
+    }
+
+    private function extract($promise)
+    {
+        if ($promise instanceof LazyPromise) {
+            $promise = $promise->promise();
+        }
+
+        if ($promise === $this) {
+            return new RejectedPromise(
+                new \LogicException('Cannot resolve a promise with itself.')
+            );
         }
 
-        return $this->result;
+        return $promise;
     }
 
     private function call(callable $callback)