[Console] Rework the signal integration

Author: lyrixx

Application.php

@@ -14,6 +14,7 @@
 use Symfony\Component\Console\Command\Command;
 use Symfony\Component\Console\Command\HelpCommand;
 use Symfony\Component\Console\Command\ListCommand;
+use Symfony\Component\Console\Command\SignalableCommandInterface;
 use Symfony\Component\Console\CommandLoader\CommandLoaderInterface;
 use Symfony\Component\Console\Event\ConsoleCommandEvent;
 use Symfony\Component\Console\Event\ConsoleErrorEvent;
@@ -79,13 +80,18 @@ class Application implements ResetInterface
     private $singleCommand = false;
     private $initialized;
     private $signalRegistry;
+    private $signalsToDispatchEvent = [];
 
     public function __construct(string $name = 'UNKNOWN', string $version = 'UNKNOWN')
     {
         $this->name = $name;
         $this->version = $version;
         $this->terminal = new Terminal();
         $this->defaultCommand = 'list';
+        $this->signalRegistry = new SignalRegistry();
+        if (\defined('SIGINT')) {
+            $this->signalsToDispatchEvent = [SIGINT, SIGTERM, SIGUSR1, SIGUSR2];
+        }
     }
 
     /**
@@ -101,9 +107,14 @@ public function setCommandLoader(CommandLoaderInterface $commandLoader)
         $this->commandLoader = $commandLoader;
     }
 
-    public function setSignalRegistry(SignalRegistry $signalRegistry)
+    public function getSignalRegistry(): SignalRegistry
     {
-        $this->signalRegistry = $signalRegistry;
+        return $this->signalRegistry;
+    }
+
+    public function setSignalsToDispatchEvent(int ...$signalsToDispatchEvent)
+    {
+        $this->signalsToDispatchEvent = $signalsToDispatchEvent;
     }
 
     /**
@@ -268,14 +279,20 @@ public function doRun(InputInterface $input, OutputInterface $output)
             $command = $this->find($alternative);
         }
 
-        if ($this->signalRegistry) {
-            foreach ($this->signalRegistry->getHandlingSignals() as $handlingSignal) {
-                $event = new ConsoleSignalEvent($command, $input, $output, $handlingSignal);
-                $onSignalHandler = function () use ($event) {
+        if ($this->dispatcher) {
+            foreach ($this->signalsToDispatchEvent as $signal) {
+                $event = new ConsoleSignalEvent($command, $input, $output, $signal);
+
+                $this->signalRegistry->register($signal, function ($signal, $hasNext) use ($event) {
                     $this->dispatcher->dispatch($event, ConsoleEvents::SIGNAL);
-                };
 
-                $this->signalRegistry->register($handlingSignal, $onSignalHandler);
+                    // No more handlers, we try to simulate PHP default behavior
+                    if (!$hasNext) {
+                        if (!\in_array($signal, [SIGUSR1, SIGUSR2], true)) {
+                            exit(0);
+                        }
+                    }
+                });
             }
         }
 
@@ -926,6 +943,12 @@ protected function doRunCommand(Command $command, InputInterface $input, OutputI
             }
         }
 
+        if ($command instanceof SignalableCommandInterface) {
+            foreach ($command->getSubscribedSignals() as $signal) {
+                $this->signalRegistry->register($signal, [$command, 'handleSignal']);
+            }
+        }
+
         if (null === $this->dispatcher) {
             return $command->run($input, $output);
         }

CHANGELOG.md

@@ -7,6 +7,10 @@ CHANGELOG
  * Added `SingleCommandApplication::setAutoExit()` to allow testing via `CommandTester`
  * added support for multiline responses to questions through `Question::setMultiline()`
    and `Question::isMultiline()`
+ * Added `SignalRegistry` class to stack signals handlers
+ * Added support for signals:
+    * Added `Application::getSignalRegistry()` and `Application::setSignalsToDispatchEvent()` methods
+    * Added `SignalableCommandInterface` interface
 
 5.1.0
 -----

Command/SignalableCommandInterface.php

@@ -0,0 +1,30 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Console\Command;
+
+/**
+ * Interface for command reacting to signal.
+ *
+ * @author Grégoire Pineau <lyrixx@lyrix.info>
+ */
+interface SignalableCommandInterface
+{
+    /**
+     * Returns the list of signals to subscribe.
+     */
+    public function getSubscribedSignals(): array;
+
+    /**
+     * The method will be called when the application is signaled.
+     */
+    public function handleSignal(int $signal): void;
+}

SignalRegistry/SignalRegistry.php

@@ -13,26 +13,27 @@
 
 final class SignalRegistry
 {
-    private $registeredSignals = [];
-
-    private $handlingSignals = [];
+    private $signalHandlers = [];
 
     public function __construct()
     {
-        pcntl_async_signals(true);
+        if (\function_exists('pcntl_async_signals')) {
+            pcntl_async_signals(true);
+        }
     }
 
     public function register(int $signal, callable $signalHandler): void
     {
-        if (!isset($this->registeredSignals[$signal])) {
+        if (!isset($this->signalHandlers[$signal])) {
             $previousCallback = pcntl_signal_get_handler($signal);
 
             if (\is_callable($previousCallback)) {
-                $this->registeredSignals[$signal][] = $previousCallback;
+                $this->signalHandlers[$signal][] = $previousCallback;
             }
         }
 
-        $this->registeredSignals[$signal][] = $signalHandler;
+        $this->signalHandlers[$signal][] = $signalHandler;
+
         pcntl_signal($signal, [$this, 'handle']);
     }
 
@@ -41,20 +42,11 @@ public function register(int $signal, callable $signalHandler): void
      */
     public function handle(int $signal): void
     {
-        foreach ($this->registeredSignals[$signal] as $signalHandler) {
-            $signalHandler($signal);
-        }
-    }
+        $count = \count($this->signalHandlers[$signal]);
 
-    public function addHandlingSignals(int ...$signals): void
-    {
-        foreach ($signals as $signal) {
-            $this->handlingSignals[$signal] = true;
+        foreach ($this->signalHandlers[$signal] as $i => $signalHandler) {
+            $hasNext = $i !== $count - 1;
+            $signalHandler($signal, $hasNext);
         }
     }
-
-    public function getHandlingSignals(): array
-    {
-        return array_keys($this->handlingSignals);
-    }
 }