Add Amp\call()

lib/functions.php

@@ -55,6 +55,33 @@ function coroutine(callable $worker): callable {
     };
 }
 
+/**
+ * Calls the given function, always returning a promise. If the function returns a Generator, it will be run as a
+ * coroutine. If the function throws, a failed promise will be returned.
+ *
+ * @param callable(mixed ...$args): mixed $functor
+ * @param array ...$args Arguments to pass to the function.
+ *
+ * @return \AsyncInterop\Promise
+ */
+function call(callable $functor, ...$args): Promise {
+    try {
+        $result = $functor(...$args);
+    } catch (\Throwable $exception) {
+        return new Failure($exception);
+    }
+
+    if ($result instanceof \Generator) {
+        return new Coroutine($result);
+    }
+
+    if (!$result instanceof Promise) {
+        return new Success($result);
+    }
+
+    return $result;
+}
+
 /**
  * Registers a callback that will forward the failure reason to the Loop error handler if the promise fails.
  *

test/CallTest.php

@@ -0,0 +1,77 @@
+<?php
+
+namespace Amp\Test;
+
+use Amp;
+use Amp\{ Coroutine, Success };
+use AsyncInterop\Promise;
+
+class CallTest extends \PHPUnit_Framework_TestCase {
+    public function testCallWithFunctionReturningPromise() {
+        $value = 1;
+        $promise = Amp\call(function ($value) {
+            return new Success($value);
+        }, $value);
+
+        $this->assertInstanceOf(Promise::class, $promise);
+
+        $promise->when(function ($exception, $value) use (&$reason, &$result) {
+            $reason = $exception;
+            $result = $value;
+        });
+
+        $this->assertNull($reason);
+        $this->assertSame($value, $result);
+    }
+
+    public function testCallWithFunctionReturningValue() {
+        $value = 1;
+        $promise = Amp\call(function ($value) {
+            return $value;
+        }, $value);
+
+        $this->assertInstanceOf(Promise::class, $promise);
+
+        $promise->when(function ($exception, $value) use (&$reason, &$result) {
+            $reason = $exception;
+            $result = $value;
+        });
+
+        $this->assertNull($reason);
+        $this->assertSame($value, $result);
+    }
+
+    public function testCallWithThrowingFunction() {
+        $exception = new \Exception;
+        $promise = Amp\call(function () use ($exception) {
+            throw $exception;
+        });
+
+        $this->assertInstanceOf(Promise::class, $promise);
+
+        $promise->when(function ($exception, $value) use (&$reason, &$result) {
+            $reason = $exception;
+            $result = $value;
+        });
+
+        $this->assertSame($exception, $reason);
+        $this->assertNull($result);
+    }
+
+    public function testCallWithGeneratorFunction() {
+        $value = 1;
+        $promise = Amp\call(function ($value) {
+            return yield new Success($value);
+        }, $value);
+
+        $this->assertInstanceOf(Coroutine::class, $promise);
+
+        $promise->when(function ($exception, $value) use (&$reason, &$result) {
+            $reason = $exception;
+            $result = $value;
+        });
+
+        $this->assertNull($reason);
+        $this->assertSame($value, $result);
+    }
+}