Add Generic PromiseWrapper class

Author: mcg-web

src/Promise/PromiseInterface.php

@@ -7,8 +7,23 @@ interface PromiseInterface
      * Waits until the promise completes if possible.
      *
      * @return mixed
-     * @throws \LogicException if the promise has no wait function or if the
-     *                         promise does not settle after waiting.
+     * @throws \LogicException if the promise has no wait function.
      */
     public function wait();
+
+    /**
+     * Appends fulfillment and rejection handlers to the promise, and returns
+     * a new promise resolving to the return value of the called handler.
+     *
+     * @param callable $onFulfilled Invoked when the promise fulfills
+     * @param callable $onRejected  Invoked when the promise is rejected
+     *
+     * @return PromiseInterface
+     *
+     * @throws \LogicException if the promise has no then function.
+     */
+    public function then(
+        callable $onFulfilled = null,
+        callable $onRejected = null
+    );
 }

src/Promise/PromiseWrapper.php

@@ -0,0 +1,85 @@
+<?php
+
+namespace GraphQL\Promise;
+
+class PromiseWrapper implements PromiseInterface
+{
+    private $wrappedPromise;
+
+    /**
+     * PromiseWrapper constructor.
+     * @param $promise
+     */
+    public function __construct($promise = null)
+    {
+        if (null !== $promise) {
+            $this->setWrappedPromise($promise);
+        }
+    }
+    /**
+     * @param $promise
+     * @return self
+     */
+    public static function wrap($promise)
+    {
+        return new static($promise);
+    }
+    /**
+     * Waits until the promise completes if possible.
+     *
+     * @return mixed
+     * @throws \LogicException if the promise has no wait function.
+     */
+    public function wait()
+    {
+        if (!$this->objectHasMethod($this->wrappedPromise, 'wait')) {
+            throw new \LogicException('Promise does not implement "wait" method');
+        }
+
+        return $this->wrappedPromise->wait();
+    }
+    /**
+     * Appends fulfillment and rejection handlers to the promise, and returns
+     * a new promise resolving to the return value of the called handler.
+     *
+     * @param callable $onFulfilled Invoked when the promise fulfills
+     * @param callable $onRejected Invoked when the promise is rejected
+     *
+     * @return $this
+     *
+     * @throws \LogicException if the promise has no then function.
+     */
+    public function then(
+        callable $onFulfilled = null,
+        callable $onRejected = null
+    )
+    {
+        if (null === $onFulfilled && null === $onRejected) {
+            return $this;
+        }
+        $newWrappedPromise = $this->getWrappedPromise()->then($onFulfilled, $onRejected);
+
+        return $this->setWrappedPromise($newWrappedPromise);
+    }
+
+    public function getWrappedPromise()
+    {
+        return $this->wrappedPromise;
+    }
+
+    public function setWrappedPromise($wrappedPromise)
+    {
+        if (!$this->objectHasMethod($wrappedPromise, 'then')) {
+            throw new \LogicException('Promise does not implement "then" method');
+        }
+
+        $this->wrappedPromise = $wrappedPromise;
+
+        return $this;
+    }
+
+    protected function objectHasMethod($object, $method)
+    {
+        return is_object($object) && is_callable([$object, $method]);
+    }
+}

tests/Promise/FakePromise.php renamed to tests/Promise/CliPromise.php

@@ -1,9 +1,7 @@
 <?php
 namespace GraphQL\Tests\Promise;
 
-use GraphQL\Promise\PromiseInterface;
-
-class FakePromise implements PromiseInterface
+class CliPromise
 {
     private $pid;
     private $outputFile;
@@ -29,6 +27,11 @@ public function wait()
         return $log;
     }
 
+    public function then()
+    {
+        return $this;
+    }
+
     private function isTerminated()
     {
         try {

tests/Promise/InvalidPromise/NoThenMethod.php

@@ -0,0 +1,6 @@
+<?php
+namespace GraphQL\Tests\Promise\InvalidPromise;
+
+class NoThenMethod
+{
+}

tests/Promise/InvalidPromise/NoWaitMethod.php

@@ -0,0 +1,10 @@
+<?php
+namespace GraphQL\Tests\Promise\InvalidPromise;
+
+class NoWaitMethod
+{
+    public function then()
+    {
+        return $this;
+    }
+}

tests/Promise/InvalidPromise/ThenReturnsInvalidPromiseMethod.php

@@ -0,0 +1,10 @@
+<?php
+namespace GraphQL\Tests\Promise\InvalidPromise;
+
+class ThenReturnsInvalidPromiseMethod
+{
+    public function then()
+    {
+        return new NoThenMethod();
+    }
+}

tests/Promise/PromiseTest.php

@@ -2,6 +2,7 @@
 namespace GraphQL\Tests\Promise;
 
 use GraphQL\GraphQL;
+use GraphQL\Promise\PromiseWrapper;
 use GraphQL\Schema;
 use GraphQL\Type\Definition\ObjectType;
 use GraphQL\Type\Definition\Type;
@@ -24,7 +25,7 @@ public function testAsyncResolving()
                 'log' => [
                     'type' => $logType,
                     'resolve' => function () {
-                        return new FakePromise('`which composer` diagnose');
+                        return PromiseWrapper::wrap(new CliPromise('`which composer` diagnose'));
                     },
                 ],
             ],

tests/Promise/PromiseWrapperTest.php

@@ -0,0 +1,52 @@
+<?php
+namespace GraphQL\Tests\Promise;
+
+use GraphQL\GraphQL;
+use GraphQL\Promise\PromiseWrapper;
+use GraphQL\Schema;
+use GraphQL\Tests\Promise\InvalidPromise\NoThenMethod;
+use GraphQL\Tests\Promise\InvalidPromise\NoWaitMethod;
+use GraphQL\Tests\Promise\InvalidPromise\ThenReturnsInvalidPromiseMethod;
+use GraphQL\Type\Definition\ObjectType;
+use GraphQL\Type\Definition\Type;
+
+class PromiseWrapperTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * @expectedException \LogicException
+     * @expectedExceptionMessage Promise does not implement "then" method
+     */
+    public function testWrapNotObject()
+    {
+        PromiseWrapper::wrap([]);
+    }
+
+    /**
+     * @expectedException \LogicException
+     * @expectedExceptionMessage Promise does not implement "then" method
+     */
+    public function testWrapObjectWithoutThenMethod()
+    {
+        PromiseWrapper::wrap(new NoThenMethod());
+    }
+
+    /**
+     * @expectedException \LogicException
+     * @expectedExceptionMessage Promise does not implement "wait" method
+     */
+    public function testWrapObjectWithoutWaitMethod()
+    {
+        $promise = PromiseWrapper::wrap(new NoWaitMethod());
+        $promise->wait();
+    }
+
+    /**
+     * @expectedException \LogicException
+     * @expectedExceptionMessage Promise does not implement "then" method
+     */
+    public function testWrapObjectThenReturnsInvalidPromise()
+    {
+        $promise = PromiseWrapper::wrap(new ThenReturnsInvalidPromiseMethod());
+        $promise->then(function() {});
+    }
+}