feature #24300 [HttpKernel][FrameworkBundle] Add a minimalist default…

… PSR-3 logger (dunglas)

This PR was squashed before being merged into the 3.4 branch (closes #24300).

Discussion
----------

[HttpKernel][FrameworkBundle] Add a minimalist default PSR-3 logger

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | no
| New feature?  | yes <!-- don't forget updating src/**/CHANGELOG.md files -->
| BC breaks?    | no
| Deprecations? | no <!-- don't forget updating UPGRADE-*.md files -->
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

This PR provides a minimalist PSR-3 logger that is always available when FrameworkBundle is installed.
By default, it writes errors on `stderr`, regular logs on `stdout` and discards debug data (this is configurable).

This approach has several benefits:

- It's what expect from an app logging systems of major containerization and orchestration tools including [Docker](https://docs.docker.com/engine/admin/logging/view_container_logs/) and [Kubernetes](https://kubernetes.io/docs/concepts/cluster-administration/logging/), as well as most cloud providers such as [Heroku](https://devcenter.heroku.com/articles/logging#writing-to-your-log) and [Google Container Engine](https://kubernetes.io/docs/tasks/debug-application-cluster/logging-stackdriver/). If the app follows this standard (and it's not currently the case with Symfony by default) logs will be automatically collected, aggregated and stored.
- It's in sync with the "back to Unix roots" philosophy of Flex
- Logs are directly displayed in the console when running the integrated PHP web server (`bin/console server:start` or Flex's `make serve`), Create React App also do that for instance.
- It fixes a common problem when installing Flex recipes: many bundles expect a logger service but currently there is none available by default, and you usually get a `"logger" service not found error` (because packages depend of the PSR, but the PSR doesn't provide a logger service).

Commits
-------

9a06513 [HttpKernel][FrameworkBundle] Add a minimalist default PSR-3 logger

composer.json

@@ -109,6 +109,7 @@
     "provide": {
         "psr/cache-implementation": "1.0",
         "psr/container-implementation": "1.0",
+        "psr/log-implementation": "1.0",
         "psr/simple-cache-implementation": "1.0"
     },
     "autoload": {

src/Symfony/Bundle/FrameworkBundle/CHANGELOG.md

@@ -4,6 +4,7 @@ CHANGELOG
 3.4.0
 -----
 
+ * Always register a minimalist logger that writes in `stderr`
  * Deprecated `profiler.matcher` option
  * Added support for `EventSubscriberInterface` on `MicroKernelTrait`
  * Removed `doctrine/cache` from the list of required dependencies in `composer.json`

src/Symfony/Bundle/FrameworkBundle/FrameworkBundle.php

@@ -28,6 +28,7 @@
 use Symfony\Component\Console\Application;
 use Symfony\Component\Console\DependencyInjection\AddConsoleCommandPass;
 use Symfony\Component\HttpKernel\DependencyInjection\ControllerArgumentValueResolverPass;
+use Symfony\Component\HttpKernel\DependencyInjection\LoggerPass;
 use Symfony\Component\HttpKernel\DependencyInjection\RegisterControllerArgumentLocatorsPass;
 use Symfony\Component\HttpKernel\DependencyInjection\RemoveEmptyControllerArgumentLocatorsPass;
 use Symfony\Component\HttpKernel\DependencyInjection\ResettableServicePass;
@@ -82,6 +83,7 @@ public function build(ContainerBuilder $container)
     {
         parent::build($container);
 
+        $container->addCompilerPass(new LoggerPass(), PassConfig::TYPE_BEFORE_OPTIMIZATION, -32);
         $container->addCompilerPass(new RegisterControllerArgumentLocatorsPass());
         $container->addCompilerPass(new RemoveEmptyControllerArgumentLocatorsPass(), PassConfig::TYPE_BEFORE_REMOVING);
         $container->addCompilerPass(new RoutingResolverPass());

src/Symfony/Component/Console/Logger/ConsoleLogger.php

@@ -101,6 +101,8 @@ public function log($level, $message, array $context = array())
 
     /**
      * Returns true when any messages have been logged at error levels.
+     *
+     * @return bool
      */
     public function hasErrored()
     {

src/Symfony/Component/HttpKernel/CHANGELOG.md

@@ -4,6 +4,7 @@ CHANGELOG
 3.4.0
 -----
 
+ * added a minimalist PSR-3 `Logger` class that writes in `stderr`
  * made kernels implementing `CompilerPassInterface` able to process the container
  * deprecated bundle inheritance
  * added `RebootableInterface` and implemented it in `Kernel`

src/Symfony/Component/HttpKernel/DependencyInjection/LoggerPass.php

@@ -0,0 +1,45 @@
+<?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\HttpKernel\DependencyInjection;
+
+use Psr\Log\LoggerInterface;
+use Psr\Log\LogLevel;
+use Symfony\Component\HttpKernel\Log\Logger;
+use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+
+/**
+ * Registers the default logger if necessary.
+ *
+ * @author Kévin Dunglas <dunglas@gmail.com>
+ */
+class LoggerPass implements CompilerPassInterface
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function process(ContainerBuilder $container)
+    {
+        $alias = $container->setAlias(LoggerInterface::class, 'logger');
+        $alias->setPublic(false);
+
+        if ($container->has('logger')) {
+            return;
+        }
+
+        $loggerDefinition = $container->register('logger', Logger::class);
+        $loggerDefinition->setPublic(false);
+        if ($container->getParameter('kernel.debug')) {
+            $loggerDefinition->addArgument(LogLevel::DEBUG);
+        }
+    }
+}

src/Symfony/Component/HttpKernel/Log/Logger.php

@@ -0,0 +1,98 @@
+<?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\HttpKernel\Log;
+
+use Psr\Log\AbstractLogger;
+use Psr\Log\InvalidArgumentException;
+use Psr\Log\LogLevel;
+
+/**
+ * Minimalist PSR-3 logger designed to write in stderr or any other stream.
+ *
+ * @author Kévin Dunglas <dunglas@gmail.com>
+ */
+class Logger extends AbstractLogger
+{
+    private static $levels = array(
+        LogLevel::DEBUG => 0,
+        LogLevel::INFO => 1,
+        LogLevel::NOTICE => 2,
+        LogLevel::WARNING => 3,
+        LogLevel::ERROR => 4,
+        LogLevel::CRITICAL => 5,
+        LogLevel::ALERT => 6,
+        LogLevel::EMERGENCY => 7,
+    );
+
+    private $minLevelIndex;
+    private $formatter;
+    private $handle;
+
+    public function __construct($minLevel = LogLevel::WARNING, $output = 'php://stderr', callable $formatter = null)
+    {
+        if (!isset(self::$levels[$minLevel])) {
+            throw new InvalidArgumentException(sprintf('The log level "%s" does not exist.', $minLevel));
+        }
+
+        $this->minLevelIndex = self::$levels[$minLevel];
+        $this->formatter = $formatter ?: array($this, 'format');
+        if (false === $this->handle = @fopen($output, 'a')) {
+            throw new InvalidArgumentException(sprintf('Unable to open "%s".', $output));
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function log($level, $message, array $context = array())
+    {
+        if (!isset(self::$levels[$level])) {
+            throw new InvalidArgumentException(sprintf('The log level "%s" does not exist.', $level));
+        }
+
+        if (self::$levels[$level] < $this->minLevelIndex) {
+            return;
+        }
+
+        $formatter = $this->formatter;
+        fwrite($this->handle, $formatter($level, $message, $context));
+    }
+
+    /**
+     * @param string $level
+     * @param string $message
+     * @param array  $context
+     *
+     * @return string
+     */
+    private function format($level, $message, array $context)
+    {
+        if (false !== strpos($message, '{')) {
+            $replacements = array();
+            foreach ($context as $key => $val) {
+                if (null === $val || is_scalar($val) || (\is_object($val) && method_exists($val, '__toString'))) {
+                    $replacements["{{$key}}"] = $val;
+                } elseif ($val instanceof \DateTimeInterface) {
+                    $replacements["{{$key}}"] = $val->format(\DateTime::RFC3339);
+                } elseif (\is_object($val)) {
+                    $replacements["{{$key}}"] = '[object '.\get_class($val).']';
+                } else {
+                    $replacements["{{$key}}"] = '['.\gettype($val).']';
+                }
+            }
+
+            $message = strtr($message, $replacements);
+        }
+
+        return sprintf('%s [%s] %s', date(\DateTime::RFC3339), $level, $message).\PHP_EOL;
+    }
+}

src/Symfony/Component/HttpKernel/Tests/DependencyInjection/LoggerPassTest.php

@@ -0,0 +1,68 @@
+<?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\HttpKernel\Tests\DependencyInjection;
+
+use PHPUnit\Framework\TestCase;
+use Psr\Log\LoggerInterface;
+use Psr\Log\LogLevel;
+use Symfony\Component\HttpKernel\DependencyInjection\LoggerPass;
+use Symfony\Component\HttpKernel\Log\Logger;
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+
+/**
+ * @author Kévin Dunglas <dunglas@gmail.com>
+ */
+class LoggerPassTest extends TestCase
+{
+    public function testAlwaysSetAutowiringAlias()
+    {
+        $container = new ContainerBuilder();
+        $container->register('logger', 'Foo');
+
+        (new LoggerPass())->process($container);
+
+        $this->assertFalse($container->getAlias(LoggerInterface::class)->isPublic());
+    }
+
+    public function testDoNotOverrideExistingLogger()
+    {
+        $container = new ContainerBuilder();
+        $container->register('logger', 'Foo');
+
+        (new LoggerPass())->process($container);
+
+        $this->assertSame('Foo', $container->getDefinition('logger')->getClass());
+    }
+
+    public function testRegisterLogger()
+    {
+        $container = new ContainerBuilder();
+        $container->setParameter('kernel.debug', false);
+
+        (new LoggerPass())->process($container);
+
+        $definition = $container->getDefinition('logger');
+        $this->assertSame(Logger::class, $definition->getClass());
+        $this->assertFalse($definition->isPublic());
+    }
+
+    public function testSetMinLevelWhenDebugging()
+    {
+        $container = new ContainerBuilder();
+        $container->setParameter('kernel.debug', true);
+
+        (new LoggerPass())->process($container);
+
+        $definition = $container->getDefinition('logger');
+        $this->assertSame(LogLevel::DEBUG, $definition->getArgument(0));
+    }
+}