Use BlockingDriver within parallel workers

Prevents infinite spawning of workers if ParallelDriver is used within a worker.

Author: trowski

composer.json

@@ -34,7 +34,7 @@
     "require": {
         "amphp/amp": "^2",
         "amphp/byte-stream": "^1",
-        "amphp/parallel": "^0.1.5"
+        "amphp/parallel": "^0.1.8"
     },
     "require-dev": {
         "amphp/phpunit-util": "^1",

lib/Internal/FileTask.php

@@ -12,7 +12,7 @@
  *
  * @internal
  */
-class FileTask extends BlockingDriver implements Task {
+class FileTask implements Task {
     const ENV_PREFIX = self::class . '#';
 
     /** @var string */
@@ -142,7 +142,7 @@ public function run(Environment $environment) {
             case "ctime":
             case "get":
             case "put":
-                return ([$this, $this->operation])(...$this->args);
+                return ([new BlockingDriver, $this->operation])(...$this->args);
 
             default:
                 throw new \Error("Invalid operation");

lib/functions.php

@@ -22,6 +22,11 @@ function filesystem(Driver $driver = null): Driver {
 
         $driver = driver();
     }
+
+    if (\defined("AMP_WORKER") && $driver instanceof ParallelDriver) {
+        throw new \Error("Cannot use the parallel driver within a worker");
+    }
+
     Loop::setState(LOOP_STATE_IDENTIFIER, $driver);
     return $driver;
 }
@@ -46,6 +51,10 @@ function driver(): Driver {
         return new BlockingDriver;
     }
 
+    if (\defined("AMP_WORKER")) { // Prevent spawning infinite workers.
+        return new BlockingDriver;
+    }
+
     return new ParallelDriver;
 }