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[mediawiki.git] / includes / Exception.php

<?php
/**
 * Exception class and handler.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 */

/**
 * @defgroup Exception Exception
 */

/**
 * MediaWiki exception
 *
 * @ingroup Exception
 */
class MWException extends Exception {
        var $logId;

        /**
         * Should the exception use $wgOut to output the error?
         *
         * @return bool
         */
        function useOutputPage() {
                return $this->useMessageCache() &&
                        !empty( $GLOBALS['wgFullyInitialised'] ) &&
                        !empty( $GLOBALS['wgOut'] ) &&
                        !empty( $GLOBALS['wgTitle'] );
        }

        /**
         * Can the extension use the Message class/wfMessage to get i18n-ed messages?
         *
         * @return bool
         */
        function useMessageCache() {
                global $wgLang;

                foreach ( $this->getTrace() as $frame ) {
                        if ( isset( $frame['class'] ) && $frame['class'] === 'LocalisationCache' ) {
                                return false;
                        }
                }

                return $wgLang instanceof Language;
        }

        /**
         * Run hook to allow extensions to modify the text of the exception
         *
         * @param string $name class name of the exception
         * @param array $args arguments to pass to the callback functions
         * @return string|null string to output or null if any hook has been called
         */
        function runHooks( $name, $args = array() ) {
                global $wgExceptionHooks;

                if ( !isset( $wgExceptionHooks ) || !is_array( $wgExceptionHooks ) ) {
                        return null; // Just silently ignore
                }

                if ( !array_key_exists( $name, $wgExceptionHooks ) || !is_array( $wgExceptionHooks[$name] ) ) {
                        return null;
                }

                $hooks = $wgExceptionHooks[$name];
                $callargs = array_merge( array( $this ), $args );

                foreach ( $hooks as $hook ) {
                        if ( is_string( $hook ) || ( is_array( $hook ) && count( $hook ) >= 2 && is_string( $hook[0] ) ) ) { // 'function' or array( 'class', hook' )
                                $result = call_user_func_array( $hook, $callargs );
                        } else {
                                $result = null;
                        }

                        if ( is_string( $result ) ) {
                                return $result;
                        }
                }
                return null;
        }

        /**
         * Get a message from i18n
         *
         * @param string $key message name
         * @param string $fallback default message if the message cache can't be
         *                  called by the exception
         * The function also has other parameters that are arguments for the message
         * @return string message with arguments replaced
         */
        function msg( $key, $fallback /*[, params...] */ ) {
                $args = array_slice( func_get_args(), 2 );

                if ( $this->useMessageCache() ) {
                        return wfMessage( $key, $args )->plain();
                } else {
                        return wfMsgReplaceArgs( $fallback, $args );
                }
        }

        /**
         * If $wgShowExceptionDetails is true, return a HTML message with a
         * backtrace to the error, otherwise show a message to ask to set it to true
         * to show that information.
         *
         * @return string html to output
         */
        function getHTML() {
                global $wgShowExceptionDetails;

                if ( $wgShowExceptionDetails ) {
                        return '<p>' . nl2br( htmlspecialchars( $this->getMessage() ) ) .
                                '</p><p>Backtrace:</p><p>' . nl2br( htmlspecialchars( $this->getTraceAsString() ) ) .
                                "</p>\n";
                } else {
                        return "<div class=\"errorbox\">" .
                                '[' . $this->getLogId() . '] ' .
                                gmdate( 'Y-m-d H:i:s' ) .
                                ": Fatal exception of type " . get_class( $this ) . "</div>\n" .
                                "<!-- Set \$wgShowExceptionDetails = true; " .
                                "at the bottom of LocalSettings.php to show detailed " .
                                "debugging information. -->";
                }
        }

        /**
         * Get the text to display when reporting the error on the command line.
         * If $wgShowExceptionDetails is true, return a text message with a
         * backtrace to the error.
         *
         * @return string
         */
        function getText() {
                global $wgShowExceptionDetails;

                if ( $wgShowExceptionDetails ) {
                        return $this->getMessage() .
                                "\nBacktrace:\n" . $this->getTraceAsString() . "\n";
                } else {
                        return "Set \$wgShowExceptionDetails = true; " .
                                "in LocalSettings.php to show detailed debugging information.\n";
                }
        }

        /**
         * Return the title of the page when reporting this error in a HTTP response.
         *
         * @return string
         */
        function getPageTitle() {
                return $this->msg( 'internalerror', "Internal error" );
        }

        /**
         * Get a random ID for this error.
         * This allows to link the exception to its corresponding log entry when
         * $wgShowExceptionDetails is set to false.
         *
         * @return string
         */
        function getLogId() {
                if ( $this->logId === null ) {
                        $this->logId = wfRandomString( 8 );
                }
                return $this->logId;
        }

        /**
         * Return the requested URL and point to file and line number from which the
         * exception occurred
         *
         * @return string
         */
        function getLogMessage() {
                global $wgRequest;

                $id = $this->getLogId();
                $file = $this->getFile();
                $line = $this->getLine();
                $message = $this->getMessage();

                if ( isset( $wgRequest ) && !$wgRequest instanceof FauxRequest ) {
                        $url = $wgRequest->getRequestURL();
                        if ( !$url ) {
                                $url = '[no URL]';
                        }
                } else {
                        $url = '[no req]';
                }

                return "[$id] $url   Exception from line $line of $file: $message";
        }

        /**
         * Output the exception report using HTML.
         */
        function reportHTML() {
                global $wgOut;
                if ( $this->useOutputPage() ) {
                        $wgOut->prepareErrorPage( $this->getPageTitle() );

                        $hookResult = $this->runHooks( get_class( $this ) );
                        if ( $hookResult ) {
                                $wgOut->addHTML( $hookResult );
                        } else {
                                $wgOut->addHTML( $this->getHTML() );
                        }

                        $wgOut->output();
                } else {
                        header( "Content-Type: text/html; charset=utf-8" );
                        echo "<!doctype html>\n" .
                                '<html><head>' .
                                '<title>' . htmlspecialchars( $this->getPageTitle() ) . '</title>' .
                                "</head><body>\n";

                        $hookResult = $this->runHooks( get_class( $this ) . "Raw" );
                        if ( $hookResult ) {
                                echo $hookResult;
                        } else {
                                echo $this->getHTML();
                        }

                        echo "</body></html>\n";
                }
        }

        /**
         * Output a report about the exception and takes care of formatting.
         * It will be either HTML or plain text based on isCommandLine().
         */
        function report() {
                global $wgLogExceptionBacktrace, $wgMimeType;
                $log = $this->getLogMessage();

                if ( $log ) {
                        if ( $wgLogExceptionBacktrace ) {
                                wfDebugLog( 'exception', $log . "\n" . $this->getTraceAsString() . "\n" );
                        } else {
                                wfDebugLog( 'exception', $log );
                        }
                }

                if ( defined( 'MW_API' ) ) {
                        // Unhandled API exception, we can't be sure that format printer is alive
                        header( 'MediaWiki-API-Error: internal_api_error_' . get_class( $this ) );
                        wfHttpError( 500, 'Internal Server Error', $this->getText() );
                } elseif ( self::isCommandLine() ) {
                        MWExceptionHandler::printError( $this->getText() );
                } else {
                        header( "HTTP/1.1 500 MediaWiki exception" );
                        header( "Status: 500 MediaWiki exception", true );
                        header( "Content-Type: $wgMimeType; charset=utf-8", true );

                        $this->reportHTML();
                }
        }

        /**
         * Check whether we are in command line mode or not to report the exception
         * in the correct format.
         *
         * @return bool
         */
        static function isCommandLine() {
                return !empty( $GLOBALS['wgCommandLineMode'] );
        }
}

/**
 * Exception class which takes an HTML error message, and does not
 * produce a backtrace. Replacement for OutputPage::fatalError().
 *
 * @since 1.7
 * @ingroup Exception
 */
class FatalError extends MWException {

        /**
         * @return string
         */
        function getHTML() {
                return $this->getMessage();
        }

        /**
         * @return string
         */
        function getText() {
                return $this->getMessage();
        }
}

/**
 * An error page which can definitely be safely rendered using the OutputPage.
 *
 * @since 1.7
 * @ingroup Exception
 */
class ErrorPageError extends MWException {
        public $title, $msg, $params;

        /**
         * Note: these arguments are keys into wfMessage(), not text!
         *
         * @param string|Message $title Message key (string) for page title, or a Message object
         * @param string|Message $msg Message key (string) for error text, or a Message object
         * @param array $params with parameters to wfMessage()
         */
        function __construct( $title, $msg, $params = null ) {
                $this->title = $title;
                $this->msg = $msg;
                $this->params = $params;

                // Bug 44111: Messages in the log files should be in English and not
                // customized by the local wiki. So get the default English version for
                // passing to the parent constructor. Our overridden report() below
                // makes sure that the page shown to the user is not forced to English.
                if ( $msg instanceof Message ) {
                        $enMsg = clone( $msg );
                } else {
                        $enMsg = wfMessage( $msg, $params );
                }
                $enMsg->inLanguage( 'en' )->useDatabase( false );
                parent::__construct( $enMsg->text() );
        }

        function report() {
                global $wgOut;

                $wgOut->showErrorPage( $this->title, $this->msg, $this->params );
                $wgOut->output();
        }
}

/**
 * Show an error page on a badtitle.
 * Similar to ErrorPage, but emit a 400 HTTP error code to let mobile
 * browser it is not really a valid content.
 *
 * @since 1.19
 * @ingroup Exception
 */
class BadTitleError extends ErrorPageError {
        /**
         * @param string|Message $msg A message key (default: 'badtitletext')
         * @param array $params parameter to wfMessage()
         */
        function __construct( $msg = 'badtitletext', $params = null ) {
                parent::__construct( 'badtitle', $msg, $params );
        }

        /**
         * Just like ErrorPageError::report() but additionally set
         * a 400 HTTP status code (bug 33646).
         */
        function report() {
                global $wgOut;

                // bug 33646: a badtitle error page need to return an error code
                // to let mobile browser now that it is not a normal page.
                $wgOut->setStatusCode( 400 );
                parent::report();
        }

}

/**
 * Show an error when a user tries to do something they do not have the necessary
 * permissions for.
 *
 * @since 1.18
 * @ingroup Exception
 */
class PermissionsError extends ErrorPageError {
        public $permission, $errors;

        function __construct( $permission, $errors = array() ) {
                global $wgLang;

                $this->permission = $permission;

                if ( !count( $errors ) ) {
                        $groups = array_map(
                                array( 'User', 'makeGroupLinkWiki' ),
                                User::getGroupsWithPermission( $this->permission )
                        );

                        if ( $groups ) {
                                $errors[] = array( 'badaccess-groups', $wgLang->commaList( $groups ), count( $groups ) );
                        } else {
                                $errors[] = array( 'badaccess-group0' );
                        }
                }

                $this->errors = $errors;
        }

        function report() {
                global $wgOut;

                $wgOut->showPermissionsErrorPage( $this->errors, $this->permission );
                $wgOut->output();
        }
}

/**
 * Show an error when the wiki is locked/read-only and the user tries to do
 * something that requires write access.
 *
 * @since 1.18
 * @ingroup Exception
 */
class ReadOnlyError extends ErrorPageError {
        public function __construct() {
                parent::__construct(
                        'readonly',
                        'readonlytext',
                        wfReadOnlyReason()
                );
        }
}

/**
 * Show an error when the user hits a rate limit.
 *
 * @since 1.18
 * @ingroup Exception
 */
class ThrottledError extends ErrorPageError {
        public function __construct() {
                parent::__construct(
                        'actionthrottled',
                        'actionthrottledtext'
                );
        }

        public function report() {
                global $wgOut;
                $wgOut->setStatusCode( 503 );
                parent::report();
        }
}

/**
 * Show an error when the user tries to do something whilst blocked.
 *
 * @since 1.18
 * @ingroup Exception
 */
class UserBlockedError extends ErrorPageError {
        public function __construct( Block $block ) {
                // @todo FIXME: Implement a more proper way to get context here.
                $params = $block->getPermissionsError( RequestContext::getMain() );
                parent::__construct( 'blockedtitle', array_shift( $params ), $params );
        }
}

/**
 * Shows a generic "user is not logged in" error page.
 *
 * This is essentially an ErrorPageError exception which by default uses the
 * 'exception-nologin' as a title and 'exception-nologin-text' for the message.
 * @see bug 37627
 * @since 1.20
 *
 * @par Example:
 * @code
 * if( $user->isAnon() ) {
 *      throw new UserNotLoggedIn();
 * }
 * @endcode
 *
 * Note the parameter order differs from ErrorPageError, this allows you to
 * simply specify a reason without overriding the default title.
 *
 * @par Example:
 * @code
 * if( $user->isAnon() ) {
 *      throw new UserNotLoggedIn( 'action-require-loggedin' );
 * }
 * @endcode
 *
 * @ingroup Exception
 */
class UserNotLoggedIn extends ErrorPageError {

        /**
         * @param $reasonMsg A message key containing the reason for the error.
         *        Optional, default: 'exception-nologin-text'
         * @param $titleMsg A message key to set the page title.
         *        Optional, default: 'exception-nologin'
         * @param $params Parameters to wfMessage().
         *        Optional, default: null
         */
        public function __construct(
                $reasonMsg = 'exception-nologin-text',
                $titleMsg = 'exception-nologin',
                $params = null
        ) {
                parent::__construct( $titleMsg, $reasonMsg, $params );
        }
}

/**
 * Show an error that looks like an HTTP server error.
 * Replacement for wfHttpError().
 *
 * @since 1.19
 * @ingroup Exception
 */
class HttpError extends MWException {
        private $httpCode, $header, $content;

        /**
         * Constructor
         *
         * @param $httpCode Integer: HTTP status code to send to the client
         * @param string|Message $content content of the message
         * @param string|Message $header content of the header (\<title\> and \<h1\>)
         */
        public function __construct( $httpCode, $content, $header = null ) {
                parent::__construct( $content );
                $this->httpCode = (int)$httpCode;
                $this->header = $header;
                $this->content = $content;
        }

        /**
         * Returns the HTTP status code supplied to the constructor.
         *
         * @return int
         */
        public function getStatusCode() {
                return $this->httpCode;
        }

        /**
         * Report the HTTP error.
         * Sends the appropriate HTTP status code and outputs an
         * HTML page with an error message.
         */
        public function report() {
                $httpMessage = HttpStatus::getMessage( $this->httpCode );

                header( "Status: {$this->httpCode} {$httpMessage}", true, $this->httpCode );
                header( 'Content-type: text/html; charset=utf-8' );

                print $this->getHTML();
        }

        /**
         * Returns HTML for reporting the HTTP error.
         * This will be a minimal but complete HTML document.
         *
         * @return string HTML
         */
        public function getHTML() {
                if ( $this->header === null ) {
                        $header = HttpStatus::getMessage( $this->httpCode );
                } elseif ( $this->header instanceof Message ) {
                        $header = $this->header->escaped();
                } else {
                        $header = htmlspecialchars( $this->header );
                }

                if ( $this->content instanceof Message ) {
                        $content = $this->content->escaped();
                } else {
                        $content = htmlspecialchars( $this->content );
                }

                return "<!DOCTYPE html>\n" .
                        "<html><head><title>$header</title></head>\n" .
                        "<body><h1>$header</h1><p>$content</p></body></html>\n";
        }
}

/**
 * Handler class for MWExceptions
 * @ingroup Exception
 */
class MWExceptionHandler {
        /**
         * Install an exception handler for MediaWiki exception types.
         */
        public static function installHandler() {
                set_exception_handler( array( 'MWExceptionHandler', 'handle' ) );
        }

        /**
         * Report an exception to the user
         */
        protected static function report( Exception $e ) {
                global $wgShowExceptionDetails;

                $cmdLine = MWException::isCommandLine();

                if ( $e instanceof MWException ) {
                        try {
                                // Try and show the exception prettily, with the normal skin infrastructure
                                $e->report();
                        } catch ( Exception $e2 ) {
                                // Exception occurred from within exception handler
                                // Show a simpler error message for the original exception,
                                // don't try to invoke report()
                                $message = "MediaWiki internal error.\n\n";

                                if ( $wgShowExceptionDetails ) {
                                        $message .= 'Original exception: ' . $e->__toString() . "\n\n" .
                                                'Exception caught inside exception handler: ' . $e2->__toString();
                                } else {
                                        $message .= "Exception caught inside exception handler.\n\n" .
                                                "Set \$wgShowExceptionDetails = true; at the bottom of LocalSettings.php " .
                                                "to show detailed debugging information.";
                                }

                                $message .= "\n";

                                if ( $cmdLine ) {
                                        self::printError( $message );
                                } else {
                                        echo nl2br( htmlspecialchars( $message ) ) . "\n";
                                }
                        }
                } else {
                        $message = "Unexpected non-MediaWiki exception encountered, of type \"" . get_class( $e ) . "\"\n" .
                                $e->__toString() . "\n";

                        if ( $wgShowExceptionDetails ) {
                                $message .= "\n" . $e->getTraceAsString() . "\n";
                        }

                        if ( $cmdLine ) {
                                self::printError( $message );
                        } else {
                                echo nl2br( htmlspecialchars( $message ) ) . "\n";
                        }
                }
        }

        /**
         * Print a message, if possible to STDERR.
         * Use this in command line mode only (see isCommandLine)
         *
         * @param string $message Failure text
         */
        public static function printError( $message ) {
                # NOTE: STDERR may not be available, especially if php-cgi is used from the command line (bug #15602).
                #      Try to produce meaningful output anyway. Using echo may corrupt output to STDOUT though.
                if ( defined( 'STDERR' ) ) {
                        fwrite( STDERR, $message );
                } else {
                        echo $message;
                }
        }

        /**
         * Exception handler which simulates the appropriate catch() handling:
         *
         *   try {
         *       ...
         *   } catch ( MWException $e ) {
         *       $e->report();
         *   } catch ( Exception $e ) {
         *       echo $e->__toString();
         *   }
         */
        public static function handle( $e ) {
                global $wgFullyInitialised;

                self::report( $e );

                // Final cleanup
                if ( $wgFullyInitialised ) {
                        try {
                                // uses $wgRequest, hence the $wgFullyInitialised condition
                                wfLogProfilingData();
                        } catch ( Exception $e ) {
                        }
                }

                // Exit value should be nonzero for the benefit of shell jobs
                exit( 1 );
        }
}