Add a couple new exceptions, both to signal configuration issues. One can be...

Add a couple new exceptions, both to signal configuration issues. One can be used to signal an error in a certain configuration, leaving to the user deciding whether it was critical or not, and what to do to deal with it. The other one indicates a configuration exception that we cannot recover from (i.e. missing files), and bootstraps a minimal configuration skeleton that we can use to go on momentarily.

lib/SimpleSAML/Error/ConfigurationError.php

+<?php
+/**
+ * This exception represents a configuration error.
+ *
+ * @author Jaime Perez Crespo, UNINETT AS <jaime.perez@uninett.no>
+ * @package SimpleSAMLphp
+ */
+
+namespace SimpleSAML\Error;
+
+
+class ConfigurationError extends \SimpleSAML_Error_Error
+{
+
+    /**
+     * The reason for this exception.
+     *
+     * @var null|string
+     */
+    protected $reason;
+
+    /**
+     * The configuration file that caused this exception.
+     *
+     * @var null|string
+     */
+    protected $config_file;
+
+
+    /**
+     * ConfigurationError constructor.
+     *
+     * @param string|null $reason The reason for this exception.
+     * @param string|null $file The configuration file that originated this error.
+     * @param array|null $config The configuration array that led to this problem.
+     */
+    public function __construct($reason = null, $file = null, array $config = null)
+    {
+        $file_str = '';
+        $reason_str = '.';
+        $params = array('CONFIG');
+        if ($file !== null) {
+            $params['%FILE%'] = $file;
+            $basepath = dirname(dirname(dirname(dirname(__FILE__)))).'/';
+            $file_str = '('.str_replace($basepath, '', $file).') ';
+        }
+        if ($reason !== null) {
+            $params['%REASON%'] = $reason;
+            $reason_str = ': '.$reason;
+        }
+        $this->reason = $reason;
+        $this->config_file = $file;
+        parent::__construct($params);
+        $this->message = 'The configuration '.$file_str.'is invalid'.$reason_str;
+    }
+
+
+    /**
+     * Get the reason for this exception.
+     *
+     * @return null|string The reason for this exception.
+     */
+    public function getReason()
+    {
+        return $this->reason;
+    }
+
+
+    /**
+     * Get the configuration file that caused this exception.
+     *
+     * @return null|string The configuration file that caused this exception.
+     */
+    public function getConfFile()
+    {
+        return $this->config_file;
+    }
+}

lib/SimpleSAML/Error/CriticalConfigurationError.php

+<?php
+/**
+ * This exception represents a configuration error that we cannot recover from.
+ *
+ * Throwing a critical configuration error indicates that the configuration available is not usable, and as such
+ * SimpleSAMLphp should not try to use it. However, in certain situations we might find a specific configuration
+ * error that makes part of the configuration unusable, while the rest we can still use. In those cases, we can
+ * just pass a configuration array to the constructor, making sure the offending configuration options are removed,
+ * reset to defaults or guessed to some usable value.
+ *
+ * If, for example, we have an error in the 'baseurlpath' configuration option, we can still load the configuration
+ * and substitute the value of that option with one guessed from the environment, using
+ * \SimpleSAML\Utils\HTTP::guessPath(). Doing so, the error is still critical, but at least we can recover up to a
+ * certain point and inform about the error in an ordered manner, without blank pages, logs out of place or even
+ * segfaults.
+ *
+ * @author Jaime Perez Crespo, UNINETT AS <jaime.perez@uninett.no>
+ * @package SimpleSAMLphp
+ */
+
+namespace SimpleSAML\Error;
+
+
+class CriticalConfigurationError extends ConfigurationError
+{
+
+    /**
+     * This is the bare minimum configuration that we can use.
+     *
+     * @var array
+     */
+    private static $minimum_config = array(
+        'logging.handler' => 'errorlog',
+        'logging.level'  => \SimpleSAML\Logger::DEBUG,
+        'errorreporting' => false,
+        'debug'          => true,
+    );
+
+
+    /**
+     * CriticalConfigurationError constructor.
+     *
+     * @param string|null $reason The reason for this critical error.
+     * @param string|null $file The configuration file that originated this error.
+     * @param array|null The configuration array that led to this problem.
+     */
+    public function __construct($reason = null, $file = null, $config = null)
+    {
+        if ($config === null) {
+            $config = self::$minimum_config;
+        } else {
+            $config['baseurlpath'] = \SimpleSAML\Utils\HTTP::guessBasePath();
+        }
+
+        \SimpleSAML_Configuration::loadFromArray(
+            $config,
+            '',
+            'simplesaml'
+        );
+        parent::__construct($reason, $file);
+    }
+
+
+    /**
+     * @param \Exception $exception
+     *
+     * @return CriticalConfigurationError
+     */
+    public static function fromException(\Exception $exception)
+    {
+        $reason = null;
+        $file = null;
+        if ($exception instanceof ConfigurationError) {
+            $reason = $exception->getReason();
+            $file = $exception->getConfFile();
+        } else {
+            $reason = $exception->getMessage();
+        }
+        return new CriticalConfigurationError($reason, $file);
+    }
+}