Merge "Minor CSS cleanup for Vector and Monobook skins"

[mediawiki.git] / includes / Hooks.php

<?php
/**
 * A tool for running hook functions.
 *
 * Copyright 2004, 2005 Evan Prodromou <evan@wikitravel.org>.
 *
 * 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
 *
 * @author Evan Prodromou <evan@wikitravel.org>
 * @see hooks.txt
 * @file
 */

/**
 * @since 1.18
 */
class MWHookException extends MWException {}

/**
 * Hooks class.
 *
 * Used to supersede $wgHooks, because globals are EVIL.
 *
 * @since 1.18
 */
class Hooks {

        protected static $handlers = array();

        /**
         * Clears hooks registered via Hooks::register(). Does not touch $wgHooks.
         * This is intended for use while testing and will fail if MW_PHPUNIT_TEST is not defined.
         *
         * @since 1.21
         *
         * @param string $name the name of the hook to clear.
         *
         * @throws MWException if not in testing mode.
         */
        public static function clear( $name ) {
                if ( !defined( 'MW_PHPUNIT_TEST' ) ) {
                        throw new MWException( 'can not reset hooks in operation.' );
                }

                unset( self::$handlers[$name] );
        }

        /**
         * Attach an event handler to a given hook
         *
         * @since 1.18
         *
         * @param string $name name of hook
         * @param $callback Mixed: callback function to attach
         */
        public static function register( $name, $callback ) {
                if( !isset( self::$handlers[$name] ) ) {
                        self::$handlers[$name] = array();
                }

                self::$handlers[$name][] = $callback;
        }

        /**
         * Returns true if a hook has a function registered to it.
         * The function may have been registered either via Hooks::register or in $wgHooks.
         *
         * @since 1.18
         *
         * @param string $name name of hook
         * @return Boolean: true if the hook has a function registered to it
         */
        public static function isRegistered( $name ) {
                global $wgHooks;

                return !empty( $wgHooks[$name] ) || !empty( self::$handlers[$name] );
        }

        /**
         * Returns an array of all the event functions attached to a hook
         * This combines functions registered via Hooks::register and with $wgHooks.
         * @since 1.18
         *
         * @throws MWException
         * @throws FatalError
         * @param string $name name of the hook
         *
         * @return array
         */
        public static function getHandlers( $name ) {
                global $wgHooks;

                // Return quickly in the most common case
                if ( empty( self::$handlers[$name] ) && empty( $wgHooks[$name] ) ) {
                        return array();
                }

                if ( !is_array( self::$handlers ) ) {
                        throw new MWException( "Local hooks array is not an array!\n" );
                }

                if ( !is_array( $wgHooks ) ) {
                        throw new MWException( "Global hooks array is not an array!\n" );
                }

                if ( empty( Hooks::$handlers[$name] ) ) {
                        $hooks = $wgHooks[$name];
                } elseif ( empty( $wgHooks[$name] ) ) {
                        $hooks = Hooks::$handlers[$name];
                } else {
                        // so they are both not empty...
                        $hooks = array_merge( Hooks::$handlers[$name], $wgHooks[$name] );
                }

                if ( !is_array( $hooks ) ) {
                        throw new MWException( "Hooks array for event '$name' is not an array!\n" );
                }

                return $hooks;
        }

        /**
         * Call hook functions defined in Hooks::register
         *
         * @param string $event event name
         * @param $args  Array: parameters passed to hook functions
         *
         * @throws MWException
         * @throws FatalError
         * @return Boolean True if no handler aborted the hook
         */
        public static function run( $event, $args = array() ) {
                global $wgHooks;

                // Return quickly in the most common case
                if ( empty( self::$handlers[$event] ) && empty( $wgHooks[$event] ) ) {
                        return true;
                }

                wfProfileIn( 'hook: ' . $event );
                $hooks = self::getHandlers( $event );

                foreach ( $hooks as $hook ) {
                        $object = null;
                        $method = null;
                        $func = null;
                        $data = null;
                        $have_data = false;
                        $closure = false;
                        $badhookmsg = false;

                        /**
                         * $hook can be: a function, an object, an array of $function and
                         * $data, an array of just a function, an array of object and
                         * method, or an array of object, method, and data.
                         */
                        if ( is_array( $hook ) ) {
                                if ( count( $hook ) < 1 ) {
                                        wfProfileOut( 'hook: ' . $event );
                                        throw new MWException( 'Empty array in hooks for ' . $event . "\n" );
                                } elseif ( is_object( $hook[0] ) ) {
                                        $object = $hook[0];
                                        if ( $object instanceof Closure ) {
                                                $closure = true;
                                                if ( count( $hook ) > 1 ) {
                                                        $data = $hook[1];
                                                        $have_data = true;
                                                }
                                        } else {
                                                if ( count( $hook ) < 2 ) {
                                                        $method = 'on' . $event;
                                                } else {
                                                        $method = $hook[1];
                                                        if ( count( $hook ) > 2 ) {
                                                                $data = $hook[2];
                                                                $have_data = true;
                                                        }
                                                }
                                        }
                                } elseif ( is_string( $hook[0] ) ) {
                                        $func = $hook[0];
                                        if ( count( $hook ) > 1 ) {
                                                $data = $hook[1];
                                                $have_data = true;
                                        }
                                } else {
                                        wfProfileOut( 'hook: ' . $event );
                                        throw new MWException( 'Unknown datatype in hooks for ' . $event . "\n" );
                                }
                        } elseif ( is_string( $hook ) ) { # functions look like strings, too
                                $func = $hook;
                        } elseif ( is_object( $hook ) ) {
                                $object = $hook;
                                if ( $object instanceof Closure ) {
                                        $closure = true;
                                } else {
                                        $method = "on" . $event;
                                }
                        } else {
                                wfProfileOut( 'hook: ' . $event );
                                throw new MWException( 'Unknown datatype in hooks for ' . $event . "\n" );
                        }

                        /* We put the first data element on, if needed. */
                        if ( $have_data ) {
                                $hook_args = array_merge( array( $data ), $args );
                        } else {
                                $hook_args = $args;
                        }

                        if ( $closure ) {
                                $callback = $object;
                                $func = "hook-$event-closure";
                        } elseif ( isset( $object ) ) {
                                $func = get_class( $object ) . '::' . $method;
                                $callback = array( $object, $method );
                        } else {
                                $callback = $func;
                        }

                        // Run autoloader (workaround for call_user_func_array bug)
                        is_callable( $callback );

                        /**
                         * Call the hook. The documentation of call_user_func_array clearly
                         * states that FALSE is returned on failure. However this is not
                         * case always. In some version of PHP if the function signature
                         * does not match the call signature, PHP will issue an warning:
                         * Param y in x expected to be a reference, value given.
                         *
                         * In that case the call will also return null. The following code
                         * catches that warning and provides better error message. The
                         * function documentation also says that:
                         *     In other words, it does not depend on the function signature
                         *     whether the parameter is passed by a value or by a reference.
                         * There is also PHP bug http://bugs.php.net/bug.php?id=47554 which
                         * is unsurprisingly marked as bogus. In short handling of failures
                         * with call_user_func_array is a failure, the documentation for that
                         * function is wrong and misleading and PHP developers don't see any
                         * problem here.
                         */
                        $retval = null;
                        set_error_handler( 'Hooks::hookErrorHandler' );
                        wfProfileIn( $func );
                        try {
                                $retval = call_user_func_array( $callback, $hook_args );
                        } catch ( MWHookException $e ) {
                                $badhookmsg = $e->getMessage();
                        }
                        wfProfileOut( $func );
                        restore_error_handler();

                        /* String return is an error; false return means stop processing. */
                        if ( is_string( $retval ) ) {
                                throw new FatalError( $retval );
                        } elseif( $retval === null ) {
                                if ( $closure ) {
                                        $prettyFunc = "$event closure";
                                } elseif( is_array( $callback ) ) {
                                        if( is_object( $callback[0] ) ) {
                                                $prettyClass = get_class( $callback[0] );
                                        } else {
                                                $prettyClass = strval( $callback[0] );
                                        }
                                        $prettyFunc = $prettyClass . '::' . strval( $callback[1] );
                                } else {
                                        $prettyFunc = strval( $callback );
                                }
                                if ( $badhookmsg ) {
                                        wfProfileOut( 'hook: ' . $event );
                                        throw new MWException(
                                                'Detected bug in an extension! ' .
                                                "Hook $prettyFunc has invalid call signature; " . $badhookmsg
                                        );
                                } else {
                                        wfProfileOut( 'hook: ' . $event );
                                        throw new MWException(
                                                'Detected bug in an extension! ' .
                                                "Hook $prettyFunc failed to return a value; " .
                                                'should return true to continue hook processing or false to abort.'
                                        );
                                }
                        } elseif ( !$retval ) {
                                wfProfileOut( 'hook: ' . $event );
                                return false;
                        }
                }

                wfProfileOut( 'hook: ' . $event );
                return true;
        }

        /**
         * This REALLY should be protected... but it's public for compatibility
         *
         * @since 1.18
         *
         * @param int $errno Unused
         * @param string $errstr error message
         * @throws MWHookException
         * @return Boolean: false
         */
        public static function hookErrorHandler( $errno, $errstr ) {
                if ( strpos( $errstr, 'expected to be a reference, value given' ) !== false ) {
                        throw new MWHookException( $errstr );
                }
                return false;
        }
}