Throw different exception for cancelled tasks

lib/Worker/Internal/TaskCancelled.php

@@ -0,0 +1,47 @@
+<?php
+
+namespace Amp\Parallel\Worker\Internal;
+
+use Amp\CancelledException;
+use Amp\Failure;
+use Amp\Parallel\Worker\TaskCancelledException;
+use Amp\Promise;
+
+/** @internal */
+final class TaskCancelled extends TaskResult
+{
+    /** @var string */
+    private $type;
+
+    /** @var int|string */
+    private $code;
+
+    /** @var array */
+    private $trace;
+
+    /** @var TaskFailure|null */
+    private $previous;
+
+    public function __construct(string $id, CancelledException $exception)
+    {
+        parent::__construct($id);
+        $this->type = \get_class($exception);
+        $this->code = $exception->getCode();
+        $this->trace = $exception->getTraceAsString();
+
+        if ($previous = $exception->getPrevious()) {
+            $this->previous = new TaskFailure($id, $previous);
+        }
+    }
+
+    public function promise(): Promise
+    {
+        $previous = $this->previous ? $this->previous->createException() : null;
+
+        return new Failure(new TaskCancelledException(
+            $this->type,
+            $this->trace,
+            $previous
+        ));
+    }
+}

lib/Worker/Internal/TaskFailure.php

@@ -50,7 +50,7 @@ final class TaskFailure extends TaskResult
         return new Failure($this->createException());
     }
 
-    private function createException(): \Throwable
+    public function createException(): \Throwable
     {
         $previous = $this->previous ? $this->previous->createException() : null;
 

lib/Worker/TaskCancelledException.php

@@ -0,0 +1,47 @@
+<?php
+
+namespace Amp\Parallel\Worker;
+
+use Amp\CancelledException;
+
+final class TaskCancelledException extends CancelledException
+{
+    /** @var string Class name of exception thrown from task. */
+    private $name;
+
+    /** @var string Stack trace of the exception thrown from task. */
+    private $trace;
+
+    /**
+     * @param string          $name     The exception class name.
+     * @param string          $trace    The exception stack trace.
+     * @param \Throwable|null $previous Previous exception.
+     */
+    public function __construct(string $name, string $trace = '', \Throwable $previous = null)
+    {
+        parent::__construct($previous);
+
+        $this->name = $name;
+        $this->trace = $trace;
+    }
+
+    /**
+     * Returns the class name of the exception thrown from the task.
+     *
+     * @return string
+     */
+    public function getName(): string
+    {
+        return $this->name;
+    }
+
+    /**
+     * Gets the stack trace at the point the exception was thrown in the task.
+     *
+     * @return string
+     */
+    public function getWorkerTrace(): string
+    {
+        return $this->trace;
+    }
+}

lib/Worker/TaskRunner.php

@@ -3,6 +3,7 @@
 namespace Amp\Parallel\Worker;
 
 use Amp\CancellationTokenSource;
+use Amp\CancelledException;
 use Amp\Coroutine;
 use Amp\Parallel\Sync\Channel;
 use Amp\Parallel\Sync\SerializationException;
@@ -57,7 +58,11 @@ final class TaskRunner
                     yield call([$job->getTask(), "run"], $this->environment, $source->getToken())
                 );
             } catch (\Throwable $exception) {
-                $result = new Internal\TaskFailure($job->getId(), $exception);
+                if ($exception instanceof CancelledException && $source->getToken()->isRequested()) {
+                    $result = new Internal\TaskCancelled($job->getId(), $exception);
+                } else {
+                    $result = new Internal\TaskFailure($job->getId(), $exception);
+                }
             } finally {
                 $resolved = true;
             }
@@ -74,6 +79,7 @@ final class TaskRunner
             $result = null; // Free memory from last result.
 
             while (!($job = yield $receive) instanceof Internal\Job && $job !== null) {
+                // Ignore possible cancellation request received after task resolved.
                 $receive = $this->channel->receive();
             }
         }

test/Worker/AbstractWorkerTest.php

@@ -9,6 +9,7 @@ use Amp\Parallel\Sync\SerializationException;
 use Amp\Parallel\Worker\BasicEnvironment;
 use Amp\Parallel\Worker\Environment;
 use Amp\Parallel\Worker\Task;
+use Amp\Parallel\Worker\TaskCancelledException;
 use Amp\Parallel\Worker\TaskError;
 use Amp\Parallel\Worker\TaskException;
 use Amp\Parallel\Worker\WorkerException;
@@ -310,8 +311,7 @@ abstract class AbstractWorkerTest extends AsyncTestCase
 
     public function testCancellableTask()
     {
-        $this->expectException(TaskException::class);
+        $this->expectException(TaskCancelledException::class);
-        $this->expectExceptionMessage('Uncaught Amp\CancelledException in worker with message "The operation was cancelled" and code "0"');
 
         $worker = $this->createWorker();
 
@@ -326,8 +326,8 @@ abstract class AbstractWorkerTest extends AsyncTestCase
 
         try {
             yield $worker->enqueue(new Fixtures\CancellingTask, new TimeoutCancellationToken(100));
-            $this->fail(TaskException::class . ' did not fail enqueue promise');
+            $this->fail(TaskCancelledException::class . ' did not fail enqueue promise');
-        } catch (TaskException $exception) {
+        } catch (TaskCancelledException $exception) {
             // Task should be cancelled, ignore this exception.
         }