Log errors that occur in the API stack

This takes place only in the FallbackExceptionHandler. Having a custom
exception handler implies that a friendly message is displayed in the
API response, in which case we can bet that the exception won't need to
be "debugged" per se.

src/Api/ApiServiceProvider.php

@@ -25,7 +25,6 @@ use Flarum\Http\RouteCollection;
 use Flarum\Http\RouteHandlerFactory;
 use Flarum\Http\UrlGenerator;
 use Tobscure\JsonApi\ErrorHandler;
-use Tobscure\JsonApi\Exception\Handler\FallbackExceptionHandler;
 use Tobscure\JsonApi\Exception\Handler\InvalidParameterExceptionHandler;
 use Zend\Stratigility\MiddlewarePipe;
 
@@ -80,7 +79,7 @@ class ApiServiceProvider extends AbstractServiceProvider
             $handler->registerHandler(new ExceptionHandler\TokenMismatchExceptionHandler);
             $handler->registerHandler(new ExceptionHandler\ValidationExceptionHandler);
             $handler->registerHandler(new InvalidParameterExceptionHandler);
-            $handler->registerHandler(new FallbackExceptionHandler($this->app->inDebugMode()));
+            $handler->registerHandler(new ExceptionHandler\FallbackExceptionHandler($this->app->inDebugMode(), $this->app->make('log')));
 
             return $handler;
         });

src/Api/ExceptionHandler/FallbackExceptionHandler.php

@@ -0,0 +1,79 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * (c) Toby Zerner <toby.zerner@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Flarum\Api\ExceptionHandler;
+
+use Exception;
+use Psr\Log\LoggerInterface;
+use Tobscure\JsonApi\Exception\Handler\ExceptionHandlerInterface;
+use Tobscure\JsonApi\Exception\Handler\ResponseBag;
+
+class FallbackExceptionHandler implements ExceptionHandlerInterface
+{
+    /**
+     * @var bool
+     */
+    protected $debug;
+
+    /**
+     * @var LoggerInterface
+     */
+    protected $logger;
+
+    /**
+     * @param bool $debug
+     * @param LoggerInterface $logger
+     */
+    public function __construct($debug, LoggerInterface $logger)
+    {
+        $this->debug = $debug;
+        $this->logger = $logger;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function manages(Exception $e)
+    {
+        return true;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function handle(Exception $e)
+    {
+        $status = 500;
+        $error = $this->constructError($e, $status);
+
+        if (! $this->debug) {
+            $this->logger->error($e);
+        }
+
+        return new ResponseBag($status, [$error]);
+    }
+
+    /**
+     * @param Exception $e
+     * @param $status
+     * @return array
+     */
+    private function constructError(Exception $e, $status)
+    {
+        $error = ['code' => $status, 'title' => 'Internal server error'];
+
+        if ($this->debug) {
+            $error['detail'] = (string) $e;
+        }
+
+        return $error;
+    }
+}