docs/hooks.txt

   1 hooks.txt
   2
   3 This document describes how event hooks work in MediaWiki; how to add
   4 hooks for an event; and how to run hooks for an event.
   5
   6 ==Glossary==
   7
   8 event
   9      Something that happens with the wiki. For example: a user logs
  10      in. A wiki page is saved. A wiki page is deleted. Often there are
  11      two events associated with a single action: one before the code
  12      is run to make the event happen, and one after. Each event has a
  13      name, preferably in CamelCase. For example, 'UserLogin',
  14      'ArticleSave', 'ArticleSaveComplete', 'ArticleDelete'.
  15
  16 hook
  17      A clump of code and data that should be run when an event
  18      happens. This can be either a function and a chunk of data, or an
  19      object and a method.
  20
  21 hook function
  22      The function part of a hook.
  23
  24 ==Rationale==
  25
  26 Hooks allow us to decouple optionally-run code from code that is run
  27 for everyone. It allows MediaWiki hackers, third-party developers and
  28 local administrators to define code that will be run at certain points
  29 in the mainline code, and to modify the data run by that mainline
  30 code. Hooks can keep mainline code simple, and make it easier to
  31 write extensions. Hooks are a principled alternative to local patches.
  32
  33 Consider, for example, two options in MediaWiki. One reverses the
  34 order of a title before displaying the article; the other converts the
  35 title to all uppercase letters. Currently, in MediaWiki code, we
  36 would handle this as follows (note: not real code, here):
  37
  38     function showAnArticle($article) {
  39         global $wgReverseTitle, $wgCapitalizeTitle;
  40
  41         if ($wgReverseTitle) {
  42             wfReverseTitle($article);
  43         }
  44
  45         if ($wgCapitalizeTitle) {
  46            wfCapitalizeTitle($article);
  47         }
  48
  49         # code to actually show the article goes here
  50     }
  51
  52 An extension writer, or a local admin, will often add custom code to
  53 the function -- with or without a global variable. For example,
  54 someone wanting email notification when an article is shown may add:
  55
  56     function showAnArticle($article) {
  57         global $wgReverseTitle, $wgCapitalizeTitle;
  58
  59         if ($wgReverseTitle) {
  60             wfReverseTitle($article);
  61         }
  62
  63         if ($wgCapitalizeTitle) {
  64            wfCapitalizeTitle($article);
  65         }
  66
  67         # code to actually show the article goes here
  68
  69         if ($wgNotifyArticle) {
  70            wfNotifyArticleShow($article));
  71         }
  72     }
  73
  74 Using a hook-running strategy, we can avoid having all this
  75 option-specific stuff in our mainline code. Using hooks, the function
  76 becomes:
  77
  78     function showAnArticle($article) {
  79
  80         if (wfRunHooks('ArticleShow', array(&$article))) {
  81
  82             # code to actually show the article goes here
  83
  84             wfRunHooks('ArticleShowComplete', array(&$article));
  85         }
  86     }
  87
  88 We've cleaned up the code here by removing clumps of weird,
  89 infrequently used code and moving them off somewhere else. It's much
  90 easier for someone working with this code to see what's _really_ going
  91 on, and make changes or fix bugs.
  92
  93 In addition, we can take all the code that deals with the little-used
  94 title-reversing options (say) and put it in one place. Instead of
  95 having little title-reversing if-blocks spread all over the codebase
  96 in showAnArticle, deleteAnArticle, exportArticle, etc., we can
  97 concentrate it all in an extension file:
  98
  99     function reverseArticleTitle($article) {
 100         # ...
 101     }
 102
 103     function reverseForExport($article) {
 104         # ...
 105     }
 106
 107 The setup function for the extension just has to add its hook
 108 functions to the appropriate events:
 109
 110     setupTitleReversingExtension() {
 111         global $wgHooks;
 112
 113         $wgHooks['ArticleShow'][] = 'reverseArticleTitle';
 114         $wgHooks['ArticleDelete'][] = 'reverseArticleTitle';
 115         $wgHooks['ArticleExport'][] = 'reverseForExport';
 116     }
 117
 118 Having all this code related to the title-reversion option in one
 119 place means that it's easier to read and understand; you don't have to
 120 do a grep-find to see where the $wgReverseTitle variable is used, say.
 121
 122 If the code is well enough isolated, it can even be excluded when not
 123 used -- making for some slight savings in memory and load-up
 124 performance at runtime. Admins who want to have all the reversed
 125 titles can add:
 126
 127     require_once('extensions/ReverseTitle.php');
 128
 129 ...to their LocalSettings.php file; those of us who don't want or need
 130 it can just leave it out.
 131
 132 The extensions don't even have to be shipped with MediaWiki; they
 133 could be provided by a third-party developer or written by the admin
 134 him/herself.
 135
 136 ==Writing hooks==
 137
 138 A hook is a chunk of code run at some particular event. It consists of:
 139
 140   * a function with some optional accompanying data, or
 141   * an object with a method and some optional accompanying data.
 142
 143 Hooks are registered by adding them to the global $wgHooks array for a
 144 given event. All the following are valid ways to define hooks:
 145
 146       $wgHooks['EventName'][] = 'someFunction'; # function, no data
 147       $wgHooks['EventName'][] = array('someFunction', $someData);
 148       $wgHooks['EventName'][] = array('someFunction'); # weird, but OK
 149
 150       $wgHooks['EventName'][] = $object; # object only
 151       $wgHooks['EventName'][] = array($object, 'someMethod');
 152       $wgHooks['EventName'][] = array($object, 'someMethod', $someData);
 153       $wgHooks['EventName'][] = array($object); # weird but OK
 154
 155 When an event occurs, the function (or object method) will be called
 156 with the optional data provided as well as event-specific parameters.
 157 The above examples would result in the following code being executed
 158 when 'EventName' happened:
 159
 160       # function, no data
 161       someFunction($param1, $param2)
 162       # function with data
 163       someFunction($someData, $param1, $param2)
 164
 165       # object only
 166       $object->onEventName($param1, $param2)
 167       # object with method
 168       $object->someMethod($param1, $param2)
 169       # object with method and data
 170       $object->someMethod($someData, $param1, $param2)
 171
 172 Note that when an object is the hook, and there's no specified method,
 173 the default method called is 'onEventName'. For different events this
 174 would be different: 'onArticleSave', 'onUserLogin', etc.
 175
 176 The extra data is useful if we want to use the same function or object
 177 for different purposes. For example:
 178
 179       $wgHooks['ArticleSaveComplete'][] = array('ircNotify', 'TimStarling');
 180       $wgHooks['ArticleSaveComplete'][] = array('ircNotify', 'brion');
 181
 182 This code would result in ircNotify being run twice when an article is
 183 saved: once for 'TimStarling', and once for 'brion'.
 184
 185 Hooks can return three possible values:
 186
 187   * true: the hook has operated successfully
 188   * "some string": an error occurred; processing should
 189           stop and the error should be shown to the user
 190   * false: the hook has successfully done the work
 191            necessary and the calling function should skip
 192
 193 The last result would be for cases where the hook function replaces
 194 the main functionality. For example, if you wanted to authenticate
 195 users to a custom system (LDAP, another PHP program, whatever), you
 196 could do:
 197
 198     $wgHooks['UserLogin'][] = array('ldapLogin', $ldapServer);
 199
 200     function ldapLogin($username, $password) {
 201         # log user into LDAP
 202         return false;
 203     }
 204
 205 Returning false makes less sense for events where the action is
 206 complete, and will normally be ignored.
 207
 208 ==Using hooks==
 209
 210 A calling function or method uses the wfRunHooks() function to run
 211 the hooks related to a particular event, like so:
 212
 213     class Article {
 214         # ...
 215         function protect() {
 216             global $wgUser;
 217             if (wfRunHooks('ArticleProtect', array(&$this, &$wgUser))) {
 218                 # protect the article
 219                 wfRunHooks('ArticleProtectComplete', array(&$this, &$wgUser));
 220             }
 221         }
 222
 223 wfRunHooks() returns true if the calling function should continue
 224 processing (the hooks ran OK, or there are no hooks to run), or false
 225 if it shouldn't (an error occurred, or one of the hooks handled the
 226 action already). Checking the return value matters more for "before"
 227 hooks than for "complete" hooks.
 228
 229 Note that hook parameters are passed in an array; this is a necessary
 230 inconvenience to make it possible to pass reference values (that can
 231 be changed) into the hook code. Also note that earlier versions of
 232 wfRunHooks took a variable number of arguments; the array() calling
 233 protocol came about after MediaWiki 1.4rc1.
 234
 235 ==Events and parameters==
 236
 237 This is a list of known events and parameters; please add to it if
 238 you're going to add events to the MediaWiki code.
 239
 240 'AbortLogin': Return false to cancel account login.
 241 $user: the User object being authenticated against
 242 $password: the password being submitted, not yet checked for validity
 243 &$retval: a LoginForm class constant to return from authenticateUserData();
 244           default is LoginForm::ABORTED. Note that the client may be using
 245           a machine API rather than the HTML user interface.
 246
 247 'AbortNewAccount': Return false to cancel account creation.
 248 $user: the User object about to be created (read-only, incomplete)
 249 $message: out parameter: error message to display on abort
 250
 251 'AddNewAccount': after a user account is created
 252 $user: the User object that was created. (Parameter added in 1.7)
 253
 254 'AlternateEdit': before checking if an user can edit a page and
 255 before showing the edit form ( EditPage::edit() ). This is triggered
 256 on &action=edit.
 257 $EditPage : the EditPage object
 258
 259 'ArticleDelete': before an article is deleted
 260 $article: the article (object) being deleted
 261 $user: the user (object) deleting the article
 262 $reason: the reason (string) the article is being deleted
 263
 264 'ArticleDeleteComplete': after an article is deleted
 265 $article: the article that was deleted
 266 $user: the user that deleted the article
 267 $reason: the reason the article was deleted
 268
 269 'ArticleProtect': before an article is protected
 270 $article: the article being protected
 271 $user: the user doing the protection
 272 $protect: boolean whether this is a protect or an unprotect
 273 $reason: Reason for protect
 274 $moveonly: boolean whether this is for move only or not
 275
 276 'ArticleProtectComplete': after an article is protected
 277 $article: the article that was protected
 278 $user: the user who did the protection
 279 $protect: boolean whether it was a protect or an unprotect
 280 $reason: Reason for protect
 281 $moveonly: boolean whether it was for move only or not
 282
 283 'ArticleSave': before an article is saved
 284 $article: the article (object) being saved
 285 $user: the user (object) saving the article
 286 $text: the new article text
 287 $summary: the article summary (comment)
 288 $isminor: minor flag
 289 $iswatch: watch flag
 290 $section: section #
 291
 292 'ArticleSaveComplete': after an article is saved
 293 $article: the article (object) saved
 294 $user: the user (object) who saved the article
 295 $text: the new article text
 296 $summary: the article summary (comment)
 297 $isminor: minor flag
 298 $iswatch: watch flag
 299 $section: section #
 300
 301 'ArticleUndeleted': When one or more revisions of an article are restored
 302 $title: Title corresponding to the article restored
 303 $create: Whether or not the restoration caused the page to be created
 304 (i.e. it didn't exist before)
 305
 306 'AuthPluginSetup': update or replace authentication plugin object ($wgAuth)
 307 Gives a chance for an extension to set it programattically to a variable class.
 308 &$auth: the $wgAuth object, probably a stub
 309
 310 'AutoAuthenticate': called to authenticate users on external/environmental means
 311 $user: writes user object to this parameter
 312
 313 'BadImage': When checking against the bad image list
 314 $name: Image name being checked
 315 &$bad: Whether or not the image is "bad"
 316
 317 Change $bad and return false to override. If an image is "bad", it is not
 318 rendered inline in wiki pages or galleries in category pages.
 319
 320 'BlockIp': before an IP address or user is blocked
 321 $block: the Block object about to be saved
 322 $user: the user _doing_ the block (not the one being blocked)
 323
 324 'BlockIpComplete': after an IP address or user is blocked
 325 $block: the Block object that was saved
 326 $user: the user who did the block (not the one being blocked)
 327
 328 'BookInformation': Before information output on Special:Booksources
 329 $isbn: ISBN to show information for
 330 $output: OutputPage object in use
 331
 332 'CustomEditor': When invoking the page editor
 333 $article: Article being edited
 334 $user: User performing the edit
 335
 336 Return true to allow the normal editor to be used, or false
 337 if implementing a custom editor, e.g. for a special namespace,
 338 etc.
 339
 340 'DiffViewHeader': called before diff display
 341 $diff: DifferenceEngine object that's calling
 342 $oldRev: Revision object of the "old" revision (may be null/invalid)
 343 $newRev: Revision object of the "new" revision
 344
 345 'EditPage::attemptSave': called before an article is
 346 saved, that is before insertNewArticle() is called
 347 &$editpage_Obj: the current EditPage object
 348
 349 'EditFormPreloadText': Allows population of the edit form when creating new pages
 350 &$text: Text to preload with
 351 &$title: Title object representing the page being created
 352
 353 'EditPage::showEditForm:fields': allows injection of form field into edit form
 354 &$editor: the EditPage instance for reference
 355 &$out: an OutputPage instance to write to
 356 return value is ignored (should always return true)
 357
 358 'EditFilter': Perform checks on an edit
 359 $editor: Edit form (see includes/EditPage.php)
 360 $text: Contents of the edit box
 361 $section: Section being edited
 362 &$error: Error message to return
 363
 364 Return false to halt editing; you'll need to handle error messages, etc. yourself.
 365 Alternatively, modifying $error and returning true will cause the contents of $error
 366 to be echoed at the top of the edit form as wikitext. Return true without altering
 367 $error to allow the edit to proceed.
 368
 369 'EmailConfirmed': When checking that the user's email address is "confirmed"
 370 $user: User being checked
 371 $confirmed: Whether or not the email address is confirmed
 372 This runs before the other checks, such as anonymity and the real check; return
 373 true to allow those checks to occur, and false if checking is done.
 374
 375 'EmailUser': before sending email from one user to another
 376 $to: address of receiving user
 377 $from: address of sending user
 378 $subject: subject of the mail
 379 $text: text of the mail
 380
 381 'EmailUserComplete': after sending email from one user to another
 382 $to: address of receiving user
 383 $from: address of sending user
 384 $subject: subject of the mail
 385 $text: text of the mail
 386
 387 'FetchChangesList': When fetching the ChangesList derivative for a particular user
 388 &$user: User the list is being fetched for
 389 &$skin: Skin object to be used with the list
 390 &$list: List object (defaults to NULL, change it to an object instance and return
 391 false override the list derivative used)
 392
 393 'FileUpload': When a file upload occurs
 394 $file : Image object representing the file that was uploaded
 395
 396 'GetInternalURL': modify fully-qualified URLs used for squid cache purging
 397 $title: Title object of page
 398 $url: string value as output (out parameter, can modify)
 399 $query: query options passed to Title::getInternalURL()
 400
 401 'GetLocalURL': modify local URLs as output into page links
 402 $title: Title object of page
 403 $url: string value as output (out parameter, can modify)
 404 $query: query options passed to Title::getLocalURL()
 405
 406 'GetFullURL': modify fully-qualified URLs used in redirects/export/offsite data
 407 $title: Title object of page
 408 $url: string value as output (out parameter, can modify)
 409 $query: query options passed to Title::getFullURL()
 410
 411 'ImageOpenShowImageInlineBefore': Call potential extension just before showing the image on an image page
 412 $imagePage: ImagePage object ($this)
 413 $output: $wgOut
 414
 415 'InternalParseBeforeLinks': during Parser's internalParse method before links but
 416 after noinclude/includeonly/onlyinclude and other processing.
 417 &$this: Parser object
 418 &$text: string containing partially parsed text
 419 &$this->mStripState: Parser's internal StripState object
 420
 421 'LoginAuthenticateAudit': a login attempt for a valid user account either succeeded or failed.
 422                           No return data is accepted; this hook is for auditing only.
 423 $user: the User object being authenticated against
 424 $password: the password being submitted and found wanting
 425 $retval: a LoginForm class constant with authenticateUserData() return value (SUCCESS, WRONG_PASS, etc)
 426
 427 'LogPageValidTypes': action being logged. DEPRECATED: Use $wgLogTypes
 428 &$type: array of strings
 429
 430 'LogPageLogName': name of the logging page(s). DEPRECATED: Use $wgLogNames
 431 &$typeText: array of strings
 432
 433 'LogPageLogHeader': strings used by wfMsg as a header. DEPRECATED: Use $wgLogHeaders
 434 &$headerText: array of strings
 435
 436 'LogPageActionText': strings used by wfMsg as a header. DEPRECATED: Use $wgLogActions
 437 &$actionText: array of strings
 438
 439 'MarkPatrolled': before an edit is marked patrolled
 440 $rcid: ID of the revision to be marked patrolled
 441 $user: the user (object) marking the revision as patrolled
 442 $wcOnlySysopsCanPatrol: config setting indicating whether the user
 443  needs to be a sysop in order to mark an edit patrolled
 444
 445 'MarkPatrolledComplete': after an edit is marked patrolled
 446 $rcid: ID of the revision marked as patrolled
 447 $user: user (object) who marked the edit patrolled
 448 $wcOnlySysopsCanPatrol: config setting indicating whether the user
 449  must be a sysop to patrol the edit
 450
 451 'MathAfterTexvc': after texvc is executed when rendering mathematics
 452 $mathRenderer: instance of MathRenderer
 453 $errmsg: error message, in HTML (string). Nonempty indicates failure
 454  of rendering the formula
 455
 456 'OutputPageBeforeHTML': a page has been processed by the parser and
 457 the resulting HTML is about to be displayed.
 458 $parserOutput: the parserOutput (object) that corresponds to the page
 459 $text: the text that will be displayed, in HTML (string)
 460
 461 'PageHistoryBeforeList': When a history page list is about to be constructed.
 462 $article: the article that the history is loading for
 463
 464 'PageHistoryLineEnding' : right before the end <li> is added to a history line
 465 $row: the revision row for this line
 466 $s: the string representing this parsed line
 467
 468 'PageRenderingHash': alter the parser cache option hash key
 469   A parser extension which depends on user options should install
 470   this hook and append its values to the key.
 471 $hash: reference to a hash key string which can be modified
 472
 473 'ParserTestTables': alter the list of tables to duplicate when parser tests
 474 are run. Use when page save hooks require the presence of custom tables
 475 to ensure that tests continue to run properly.
 476 &$tables: array of table names
 477
 478 'PersonalUrls': Alter the user-specific navigation links (e.g. "my page,
 479 my talk page, my contributions" etc).
 480
 481 &$personal_urls: Array of link specifiers (see SkinTemplate.php)
 482 &$title: Title object representing the current page
 483
 484 'PingLimiter': Allows extensions to override the results of User::pingLimiter()
 485 &$user : User performing the action
 486 $action : Action being performed
 487 &$result : Whether or not the action should be prevented
 488 Change $result and return false to give a definitive answer, otherwise
 489 the built-in rate limiting checks are used, if enabled.
 490
 491 'PreferencesUserInformationPanel': Add HTML bits to user information list in preferences form
 492 $form : PreferencesForm object
 493 &$html : HTML to append to
 494
 495 'RawPageViewBeforeOutput': Right before the text is blown out in action=raw
 496 &$obj: RawPage object
 497 &$text: The text that's going to be the output
 498
 499 'SearchUpdate': Prior to search update completion
 500 $id : Page id
 501 $namespace : Page namespace
 502 $title : Page title
 503 $text : Current text being indexed
 504
 505 'SiteNoticeBefore': Before the sitenotice/anonnotice is composed
 506 &$siteNotice: HTML returned as the sitenotice
 507 Return true to allow the normal method of notice selection/rendering to work,
 508 or change the value of $siteNotice and return false to alter it.
 509
 510 'SiteNoticeAfter': After the sitenotice/anonnotice is composed
 511 &$siteNotice: HTML sitenotice
 512 Alter the contents of $siteNotice to add to/alter the sitenotice/anonnotice.
 513
 514 'SkinTemplateOutputPageBeforeExec': Before SkinTemplate::outputPage() starts page output
 515 &$sktemplate: SkinTemplate object
 516 &$tpl: Template engine object
 517
 518 'TitleMoveComplete': after moving an article (title)
 519 $old: old title
 520 $nt: new title
 521 $user: user who did the move
 522 $pageid: database ID of the page that's been moved
 523 $redirid: database ID of the created redirect
 524
 525 'UnknownAction': An unknown "action" has occured (useful for defining
 526                  your own actions)
 527 $action: action name
 528 $article: article "acted on"
 529
 530 'UnwatchArticle': before a watch is removed from an article
 531 $user: user watching
 532 $article: article object to be removed
 533
 534 'UnwatchArticle': after a watch is removed from an article
 535 $user: user that was watching
 536 $article: article object removed
 537
 538 'UploadForm:initial': before the upload form is generated
 539 $form: UploadForm object
 540 You might set the member-variables $uploadFormTextTop and
 541 $uploadFormTextAfterSummary to inject text (HTML) either before
 542 or after the editform.
 543
 544 'UploadForm:BeforeProcessing': at the beginning of processUpload()
 545 $form: UploadForm object
 546 Lets you poke at member variables like $mUploadDescription before the
 547 file is saved.
 548
 549 'UploadVerification': additional chances to reject an uploaded file
 550 string $saveName: destination file name
 551 string $tempName: filesystem path to the temporary file for checks
 552 string &$error: output: HTML error to show if upload canceled by returning false
 553
 554 'UploadComplete': Upon completion of a file upload
 555 $image: Image object representing the file that was uploaded
 556
 557 'UserCan': To interrupt/advise the "user can do X to Y article" check
 558 $title: Title object being checked against
 559 $user : Current user object
 560 $action: Action being checked
 561 $result: Pointer to result returned if hook returns false. If null is returned,
 562  UserCan checks are continued by internal code
 563
 564 'UserCreateForm': change to manipulate the login form
 565 $template: SimpleTemplate instance for the form
 566
 567 'UserLoginComplete': after a user has logged in
 568 $user: the user object that was created on login
 569
 570 'UserLoginForm': change to manipulate the login form
 571 $template: SimpleTemplate instance for the form
 572
 573 'UserLogout': before a user logs out
 574 $user: the user object that is about to be logged out
 575
 576 'UserLogoutComplete': after a user has logged out
 577 $user: the user object _after_ logout (won't have name, ID, etc.)
 578
 579 'UserRights': After a user's group memberships are changed
 580 $user  : User object that was changed
 581 $add   : Array of strings corresponding to groups added
 582 $remove: Array of strings corresponding to groups removed
 583
 584 'WatchArticle': before a watch is added to an article
 585 $user: user that will watch
 586 $article: article object to be watched
 587
 588 'WatchArticleComplete': after a watch is added to an article
 589 $user: user that watched
 590 $article: article object watched
 591
 592 'UnwatchArticleComplete': after a watch is removed from an article
 593 $user: user that watched
 594 $article: article object that was watched
 595
 596 'CategoryPageView': before viewing a categorypage in CategoryPage::view
 597 $catpage: CategoryPage instance
 598
 599 'SkinTemplateContentActions': after building the $content_action array right
 600                               before returning it, see Content_action.php in
 601                               the extensions/examples/ directory
 602                               ( http://svn.wikimedia.org/viewvc/mediawiki/trunk/extensions/examples/ )
 603                               for a demonstration of how to use this hook.
 604 $content_actions: The array of content actions
 605
 606 'BeforePageDisplay': Called just before outputting a page (all kinds of,
 607                      articles, special, history, preview, diff, edit, ...)
 608                      Can be used to set custom CSS/JS
 609 $out: OutputPage object
 610
 611 'AjaxAddScript': Called in output page just before the initialisation
 612 of the javascript ajax engine. The hook is only called when ajax
 613 is enabled ( $wgUseAjax = true; ).
 614
 615 More hooks might be available but undocumented, you can execute
 616 ./maintenance/findhooks.php to find hidden one.