Drop support for promises

We have Awaitable now and no longer need promises. Emitter is now compatible with \Iterator. Removed many things, because they're no longer needed.

composer.json

@@ -38,7 +38,7 @@
         "concurrent-php/async-api": "dev-master"
     },
     "require-dev": {
-        "amphp/phpunit-util": "^1",
+        "amphp/phpunit-util": "dev-ext-task",
         "react/promise": "^2",
         "friendsofphp/php-cs-fixer": "^2.3",
         "phpunit/phpunit": "^6.0.9",
@@ -69,7 +69,7 @@
     },
     "config": {
         "platform": {
-            "php": "7.0.0"
+            "php": "7.2.0"
         }
     },
     "scripts": {

lib/Cancellation/CancelledException.php

@@ -0,0 +1,17 @@
+<?php
+
+namespace Amp\Cancellation;
+
+/**
+ * Will be thrown in case an operation is cancelled.
+ *
+ * @see Token
+ * @see CancellationTokenSource
+ */
+class CancelledException extends \Exception
+{
+    public function __construct(string $message = "The operation was cancelled", \Throwable $previous = null)
+    {
+        parent::__construct($message, 0, $previous);
+    }
+}

lib/NullCancellationToken.php → lib/Cancellation/NullToken.php

@@ -1,6 +1,6 @@
 <?php
 
-namespace Amp;
+namespace Amp\Cancellation;
 
 /**
  * A NullCancellationToken can be used to avoid conditionals to check whether a token has been provided.
@@ -25,7 +25,7 @@
  *
  * instead.
  */
-final class NullCancellationToken implements CancellationToken
+final class NullToken implements Token
 {
     /** @inheritdoc */
     public function subscribe(callable $callback): string
@@ -34,7 +34,7 @@ public function subscribe(callable $callback): string
     }
 
     /** @inheritdoc */
-    public function unsubscribe(string $id)
+    public function unsubscribe(string $id): void
     {
         // nothing to do
     }
@@ -46,7 +46,7 @@ public function isRequested(): bool
     }
 
     /** @inheritdoc */
-    public function throwIfRequested()
+    public function throwIfRequested(): void
     {
         // nothing to do
     }

lib/TimeoutCancellationToken.php → lib/Cancellation/TimeoutToken.php

@@ -1,24 +1,27 @@
 <?php
 
-namespace Amp;
+namespace Amp\Cancellation;
+
+use Amp\Loop;
+use Amp\TimeoutException;
 
 /**
  * A TimeoutCancellationToken automatically requests cancellation after the timeout has elapsed.
  */
-final class TimeoutCancellationToken implements CancellationToken
+final class TimeoutToken implements Token
 {
     /** @var string */
     private $watcher;
 
-    /** @var \Amp\CancellationToken */
+    /** @var Token */
     private $token;
 
     /**
      * @param int $timeout Milliseconds until cancellation is requested.
      */
     public function __construct(int $timeout)
     {
-        $source = new CancellationTokenSource;
+        $source = new TokenSource;
         $this->token = $source->getToken();
 
         $this->watcher = Loop::delay($timeout, static function () use ($source) {
@@ -46,7 +49,7 @@ public function subscribe(callable $callback): string
     /**
      * {@inheritdoc}
      */
-    public function unsubscribe(string $id)
+    public function unsubscribe(string $id): void
     {
         $this->token->unsubscribe($id);
     }
@@ -62,7 +65,7 @@ public function isRequested(): bool
     /**
      * {@inheritdoc}
      */
-    public function throwIfRequested()
+    public function throwIfRequested(): void
     {
         $this->token->throwIfRequested();
     }

lib/CancellationToken.php → lib/Cancellation/Token.php

@@ -1,11 +1,11 @@
 <?php
 
-namespace Amp;
+namespace Amp\Cancellation;
 
 /**
  * Cancellation tokens are simple objects that allow registering handlers to subscribe to cancellation requests.
  */
-interface CancellationToken
+interface Token
 {
     /**
      * Subscribes a new handler to be invoked on a cancellation request.
@@ -29,7 +29,7 @@ public function subscribe(callable $callback): string;
      *
      * @return void
      */
-    public function unsubscribe(string $id);
+    public function unsubscribe(string $id): void;
 
     /**
      * Returns whether cancellation has been requested yet.
@@ -42,6 +42,8 @@ public function isRequested(): bool;
      * Throws the `CancelledException` if cancellation has been requested, otherwise does nothing.
      *
      * @return void
+     *
+     * @throws CancelledException
      */
-    public function throwIfRequested();
+    public function throwIfRequested(): void;
 }

lib/CancellationTokenSource.php → lib/Cancellation/TokenSource.php

@@ -1,9 +1,6 @@
 <?php
 
-namespace Amp;
-
-use React\Promise\PromiseInterface as ReactPromise;
-use function Amp\Promise\rethrow;
+namespace Amp\Cancellation;
 
 /**
  * A cancellation token source provides a mechanism to cancel operations.
@@ -35,25 +32,26 @@
  * }
  * ```
  *
- * @see CancellationToken
+ * @see Token
  * @see CancelledException
  */
-final class CancellationTokenSource
+final class TokenSource
 {
     private $token;
     private $onCancel;
 
     public function __construct()
     {
-        $this->token = new class($this->onCancel) implements CancellationToken {
+        $this->token = new class($this->onCancel) implements Token
+        {
             /** @var string */
             private $nextId = "a";
 
             /** @var callable[] */
             private $callbacks = [];
 
             /** @var \Throwable|null */
-            private $exception = null;
+            private $exception;
 
             public function __construct(&$onCancel)
             {
@@ -64,79 +62,59 @@ public function __construct(&$onCancel)
                     $this->callbacks = [];
 
                     foreach ($callbacks as $callback) {
-                        $this->invokeCallback($callback);
+                        $callback($this->exception);
                     }
                 };
             }
 
-            private function invokeCallback($callback)
-            {
-                // No type declaration to prevent exception outside the try!
-                try {
-                    $result = $callback($this->exception);
-
-                    if ($result instanceof \Generator) {
-                        $result = new Coroutine($result);
-                    }
-
-                    if ($result instanceof Promise || $result instanceof ReactPromise) {
-                        rethrow($result);
-                    }
-                } catch (\Throwable $exception) {
-                    Loop::defer(static function () use ($exception) {
-                        throw $exception;
-                    });
-                }
-            }
-
             public function subscribe(callable $callback): string
             {
                 $id = $this->nextId++;
 
                 if ($this->exception) {
-                    $this->invokeCallback($callback);
+                    $callback($this->exception);
                 } else {
                     $this->callbacks[$id] = $callback;
                 }
 
                 return $id;
             }
 
-            public function unsubscribe(string $id)
+            public function unsubscribe(string $id): void
             {
                 unset($this->callbacks[$id]);
             }
 
             public function isRequested(): bool
             {
-                return isset($this->exception);
+                return $this->exception !== null;
             }
 
-            public function throwIfRequested()
+            public function throwIfRequested(): void
             {
-                if (isset($this->exception)) {
+                if ($this->exception !== null) {
                     throw $this->exception;
                 }
             }
         };
     }
 
-    public function getToken(): CancellationToken
+    public function getToken(): Token
     {
         return $this->token;
     }
 
     /**
      * @param \Throwable|null $previous Exception to be used as the previous exception to CancelledException.
      */
-    public function cancel(\Throwable $previous = null)
+    public function cancel(\Throwable $previous = null): void
     {
         if ($this->onCancel === null) {
             return;
         }
 
         $onCancel = $this->onCancel;
         $this->onCancel = null;
-        $onCancel(new CancelledException($previous));
+        $onCancel(new CancelledException("The operation was cancelled", $previous));
     }
 }