From 16572846086712f73598e0cee10f5314cef520f8 Mon Sep 17 00:00:00 2001
From: Niklas Keller <me@kelunik.com>
Date: Tue, 1 Oct 2019 21:01:44 +0200
Subject: [PATCH] Add TracingDriver for debugging (#283)

---
 lib/Loop/DriverFactory.php |  38 +++++---
 lib/Loop/TracingDriver.php | 194 +++++++++++++++++++++++++++++++++++++
 2 files changed, 217 insertions(+), 15 deletions(-)
 create mode 100644 lib/Loop/TracingDriver.php

diff --git a/lib/Loop/DriverFactory.php b/lib/Loop/DriverFactory.php
index 3cd0048..110fd0a 100644
--- a/lib/Loop/DriverFactory.php
+++ b/lib/Loop/DriverFactory.php
@@ -14,23 +14,31 @@ class DriverFactory
      */
     public function create(): Driver
     {
-        if ($driver = $this->createDriverFromEnv()) {
-            return $driver;
+        $driver = (function () {
+            if ($driver = $this->createDriverFromEnv()) {
+                return $driver;
+            }
+
+            if (UvDriver::isSupported()) {
+                return new UvDriver;
+            }
+
+            if (EvDriver::isSupported()) {
+                return new EvDriver;
+            }
+
+            if (EventDriver::isSupported()) {
+                return new EventDriver;
+            }
+
+            return new NativeDriver;
+        })();
+
+        if (\getenv("AMP_DEBUG_TRACE_WATCHERS")) {
+            return new TracingDriver($driver);
         }
 
-        if (UvDriver::isSupported()) {
-            return new UvDriver;
-        }
-
-        if (EvDriver::isSupported()) {
-            return new EvDriver;
-        }
-
-        if (EventDriver::isSupported()) {
-            return new EventDriver;
-        }
-
-        return new NativeDriver;
+        return $driver;
     }
 
     private function createDriverFromEnv()
diff --git a/lib/Loop/TracingDriver.php b/lib/Loop/TracingDriver.php
new file mode 100644
index 0000000..7ac3e97
--- /dev/null
+++ b/lib/Loop/TracingDriver.php
@@ -0,0 +1,194 @@
+<?php
+
+namespace Amp\Loop;
+
+use function Amp\Internal\formatStacktrace;
+
+final class TracingDriver extends Driver
+{
+    private $driver;
+    private $enabledWatchers = [];
+    private $unreferencedWatchers = [];
+    private $creationTraces = [];
+    private $cancelTraces = [];
+
+    public function __construct(Driver $driver)
+    {
+        $this->driver = $driver;
+    }
+
+    public function run()
+    {
+        $this->driver->run();
+    }
+
+    public function stop()
+    {
+        $this->driver->stop();
+    }
+
+    public function defer(callable $callback, $data = null): string
+    {
+        $id = $this->driver->defer(function (...$args) use ($callback) {
+            $this->cancel($args[0]);
+            return $callback(...$args);
+        }, $data);
+
+        $this->creationTraces[$id] = formatStacktrace(\debug_backtrace(\DEBUG_BACKTRACE_IGNORE_ARGS));
+        $this->enabledWatchers[$id] = true;
+        return $id;
+    }
+
+    public function delay(int $delay, callable $callback, $data = null): string
+    {
+        $id = $this->driver->delay($delay, function (...$args) use ($callback) {
+            $this->cancel($args[0]);
+            return $callback(...$args);
+        }, $data);
+
+        $this->creationTraces[$id] = formatStacktrace(\debug_backtrace(\DEBUG_BACKTRACE_IGNORE_ARGS));
+        $this->enabledWatchers[$id] = true;
+        return $id;
+    }
+
+    public function repeat(int $interval, callable $callback, $data = null): string
+    {
+        $id = $this->driver->repeat($interval, $callback, $data);
+        $this->creationTraces[$id] = formatStacktrace(\debug_backtrace(\DEBUG_BACKTRACE_IGNORE_ARGS));
+        $this->enabledWatchers[$id] = true;
+        return $id;
+    }
+
+    public function onReadable($stream, callable $callback, $data = null): string
+    {
+        $id = $this->driver->onReadable($stream, $callback, $data);
+        $this->creationTraces[$id] = formatStacktrace(\debug_backtrace(\DEBUG_BACKTRACE_IGNORE_ARGS));
+        $this->enabledWatchers[$id] = true;
+        return $id;
+    }
+
+    public function onWritable($stream, callable $callback, $data = null): string
+    {
+        $id = $this->driver->onWritable($stream, $callback, $data);
+        $this->creationTraces[$id] = formatStacktrace(\debug_backtrace(\DEBUG_BACKTRACE_IGNORE_ARGS));
+        $this->enabledWatchers[$id] = true;
+        return $id;
+    }
+
+    public function onSignal(int $signo, callable $callback, $data = null): string
+    {
+        $id = $this->driver->onSignal($signo, $callback, $data);
+        $this->creationTraces[$id] = formatStacktrace(\debug_backtrace(\DEBUG_BACKTRACE_IGNORE_ARGS));
+        $this->enabledWatchers[$id] = true;
+        return $id;
+    }
+
+    public function enable(string $watcherId)
+    {
+        try {
+            $this->driver->enable($watcherId);
+            $this->enabledWatchers[$watcherId] = true;
+        } catch (InvalidWatcherError $e) {
+            throw new InvalidWatcherError(
+                $watcherId,
+                $e->getMessage() . "\r\n\r\nCreation Trace:\r\n" . $this->getCreationTrace($watcherId) . "\r\n\r\nCancel Trace:\r\n" . $this->getCancelTrace($watcherId)
+            );
+        }
+    }
+
+    public function cancel(string $watcherId)
+    {
+        $this->driver->cancel($watcherId);
+        $this->creationTraces[$watcherId] = formatStacktrace(\debug_backtrace(\DEBUG_BACKTRACE_IGNORE_ARGS));
+        unset($this->enabledWatchers[$watcherId], $this->unreferencedWatchers[$watcherId]);
+    }
+
+    public function disable(string $watcherId)
+    {
+        $this->driver->disable($watcherId);
+        unset($this->enabledWatchers[$watcherId]);
+    }
+
+    public function reference(string $watcherId)
+    {
+        try {
+            $this->driver->reference($watcherId);
+            unset($this->unreferencedWatchers[$watcherId]);
+        } catch (InvalidWatcherError $e) {
+            throw new InvalidWatcherError(
+                $watcherId,
+                $e->getMessage() . "\r\n\r\nCreation Trace:\r\n" . $this->getCreationTrace($watcherId)
+            );
+        }
+    }
+
+    public function unreference(string $watcherId)
+    {
+        $this->driver->unreference($watcherId);
+        $this->unreferencedWatchers[$watcherId] = true;
+    }
+
+    public function setErrorHandler(callable $callback = null)
+    {
+        return $this->driver->setErrorHandler($callback);
+    }
+
+    /** @inheritdoc */
+    public function getHandle()
+    {
+        $this->driver->getHandle();
+    }
+
+    public function dump(): string
+    {
+        $dump = "Enabled, referenced watchers keeping the loop running: ";
+
+        foreach ($this->enabledWatchers as $watcher => $_) {
+            if (isset($this->unreferencedWatchers[$watcher])) {
+                continue;
+            }
+
+            $dump .= "Watcher ID: " . $watcher . "\r\n";
+            $dump .= $this->getCreationTrace($watcher);
+            $dump .= "\r\n\r\n";
+        }
+
+        return \rtrim($dump);
+    }
+
+    /** @inheritdoc */
+    protected function activate(array $watchers)
+    {
+        // nothing to do in a decorator
+    }
+
+    /** @inheritdoc */
+    protected function dispatch(bool $blocking)
+    {
+        // nothing to do in a decorator
+    }
+
+    /** @inheritdoc */
+    protected function deactivate(Watcher $watcher)
+    {
+        // nothing to do in a decorator
+    }
+
+    private function getCreationTrace(string $watcher): string
+    {
+        if (!isset($this->creationTraces[$watcher])) {
+            new InvalidWatcherError($watcher, "An invalid watcher has been used: " . $watcher);
+        }
+
+        return $this->creationTraces[$watcher];
+    }
+
+    private function getCancelTrace(string $watcher): string
+    {
+        if (!isset($this->cancelTraces[$watcher])) {
+            throw new InvalidWatcherError($watcher, "An invalid watcher has been used: " . $watcher);
+        }
+
+        return $this->cancelTraces[$watcher];
+    }
+}