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includes/api/ApiStashEdit.php (1 issue)

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<?php
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/**
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 * This program is free software; you can redistribute it and/or modify
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 * it under the terms of the GNU General Public License as published by
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 * the Free Software Foundation; either version 2 of the License, or
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 * (at your option) any later version.
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 *
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 * This program is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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 * GNU General Public License for more details.
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 *
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 * You should have received a copy of the GNU General Public License along
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 * with this program; if not, write to the Free Software Foundation, Inc.,
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 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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 * http://www.gnu.org/copyleft/gpl.html
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 *
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 * @file
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 * @author Aaron Schulz
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 */
21
22
use MediaWiki\Logger\LoggerFactory;
23
use MediaWiki\MediaWikiServices;
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use Wikimedia\ScopedCallback;
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This use statement conflicts with another class in this namespace, ScopedCallback.

Let’s assume that you have a directory layout like this:

.
|-- OtherDir
|   |-- Bar.php
|   `-- Foo.php
`-- SomeDir
    `-- Foo.php

and let’s assume the following content of Bar.php:

// Bar.php
namespace OtherDir;

use SomeDir\Foo; // This now conflicts the class OtherDir\Foo

If both files OtherDir/Foo.php and SomeDir/Foo.php are loaded in the same runtime, you will see a PHP error such as the following:

PHP Fatal error:  Cannot use SomeDir\Foo as Foo because the name is already in use in OtherDir/Foo.php

However, as OtherDir/Foo.php does not necessarily have to be loaded and the error is only triggered if it is loaded before OtherDir/Bar.php, this problem might go unnoticed for a while. In order to prevent this error from surfacing, you must import the namespace with a different alias:

// Bar.php
namespace OtherDir;

use SomeDir\Foo as SomeDirFoo; // There is no conflict anymore.
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26
/**
27
 * Prepare an edit in shared cache so that it can be reused on edit
28
 *
29
 * This endpoint can be called via AJAX as the user focuses on the edit
30
 * summary box. By the time of submission, the parse may have already
31
 * finished, and can be immediately used on page save. Certain parser
32
 * functions like {{REVISIONID}} or {{CURRENTTIME}} may cause the cache
33
 * to not be used on edit. Template and files used are check for changes
34
 * since the output was generated. The cache TTL is also kept low for sanity.
35
 *
36
 * @ingroup API
37
 * @since 1.25
38
 */
39
class ApiStashEdit extends ApiBase {
40
	const ERROR_NONE = 'stashed';
41
	const ERROR_PARSE = 'error_parse';
42
	const ERROR_CACHE = 'error_cache';
43
	const ERROR_UNCACHEABLE = 'uncacheable';
44
	const ERROR_BUSY = 'busy';
45
46
	const PRESUME_FRESH_TTL_SEC = 30;
47
	const MAX_CACHE_TTL = 300; // 5 minutes
48
49
	public function execute() {
50
		$user = $this->getUser();
51
		$params = $this->extractRequestParams();
52
53
		if ( $user->isBot() ) { // sanity
54
			$this->dieUsage( 'This interface is not supported for bots', 'botsnotsupported' );
55
		}
56
57
		$cache = ObjectCache::getLocalClusterInstance();
58
		$page = $this->getTitleOrPageId( $params );
59
		$title = $page->getTitle();
60
61
		if ( !ContentHandler::getForModelID( $params['contentmodel'] )
62
			->isSupportedFormat( $params['contentformat'] )
63
		) {
64
			$this->dieUsage( 'Unsupported content model/format', 'badmodelformat' );
65
		}
66
67
		$text = null;
68
		$textHash = null;
69
		if ( strlen( $params['stashedtexthash'] ) ) {
70
			// Load from cache since the client indicates the text is the same as last stash
71
			$textHash = $params['stashedtexthash'];
72
			$textKey = $cache->makeKey( 'stashedit', 'text', $textHash );
73
			$text = $cache->get( $textKey );
74
			if ( !is_string( $text ) ) {
75
				$this->dieUsage( 'No stashed text found with the given hash', 'missingtext' );
76
			}
77
		} elseif ( $params['text'] !== null ) {
78
			// Trim and fix newlines so the key SHA1's match (see WebRequest::getText())
79
			$text = rtrim( str_replace( "\r\n", "\n", $params['text'] ) );
80
			$textHash = sha1( $text );
81
		} else {
82
			$this->dieUsage(
83
				'The text or stashedtexthash parameter must be given', 'missingtextparam' );
84
		}
85
86
		$textContent = ContentHandler::makeContent(
87
			$text, $title, $params['contentmodel'], $params['contentformat'] );
88
89
		$page = WikiPage::factory( $title );
90
		if ( $page->exists() ) {
91
			// Page exists: get the merged content with the proposed change
92
			$baseRev = Revision::newFromPageId( $page->getId(), $params['baserevid'] );
93
			if ( !$baseRev ) {
94
				$this->dieUsage( "No revision ID {$params['baserevid']}", 'missingrev' );
95
			}
96
			$currentRev = $page->getRevision();
97
			if ( !$currentRev ) {
98
				$this->dieUsage( "No current revision of page ID {$page->getId()}", 'missingrev' );
99
			}
100
			// Merge in the new version of the section to get the proposed version
101
			$editContent = $page->replaceSectionAtRev(
102
				$params['section'],
103
				$textContent,
104
				$params['sectiontitle'],
105
				$baseRev->getId()
106
			);
107
			if ( !$editContent ) {
108
				$this->dieUsage( 'Could not merge updated section.', 'replacefailed' );
109
			}
110
			if ( $currentRev->getId() == $baseRev->getId() ) {
111
				// Base revision was still the latest; nothing to merge
112
				$content = $editContent;
113
			} else {
114
				// Merge the edit into the current version
115
				$baseContent = $baseRev->getContent();
116
				$currentContent = $currentRev->getContent();
117
				if ( !$baseContent || !$currentContent ) {
118
					$this->dieUsage( "Missing content for page ID {$page->getId()}", 'missingrev' );
119
				}
120
				$handler = ContentHandler::getForModelID( $baseContent->getModel() );
121
				$content = $handler->merge3( $baseContent, $editContent, $currentContent );
122
			}
123
		} else {
124
			// New pages: use the user-provided content model
125
			$content = $textContent;
126
		}
127
128
		if ( !$content ) { // merge3() failed
129
			$this->getResult()->addValue( null,
130
				$this->getModuleName(), [ 'status' => 'editconflict' ] );
131
			return;
132
		}
133
134
		// The user will abort the AJAX request by pressing "save", so ignore that
135
		ignore_user_abort( true );
136
137
		if ( $user->pingLimiter( 'stashedit' ) ) {
138
			$status = 'ratelimited';
139
		} else {
140
			$status = self::parseAndStash( $page, $content, $user, $params['summary'] );
141
			$textKey = $cache->makeKey( 'stashedit', 'text', $textHash );
142
			$cache->set( $textKey, $text, self::MAX_CACHE_TTL );
143
		}
144
145
		$stats = MediaWikiServices::getInstance()->getStatsdDataFactory();
146
		$stats->increment( "editstash.cache_stores.$status" );
147
148
		$this->getResult()->addValue(
149
			null,
150
			$this->getModuleName(),
151
			[
152
				'status' => $status,
153
				'texthash' => $textHash
154
			]
155
		);
156
	}
157
158
	/**
159
	 * @param WikiPage $page
160
	 * @param Content $content Edit content
161
	 * @param User $user
162
	 * @param string $summary Edit summary
163
	 * @return integer ApiStashEdit::ERROR_* constant
164
	 * @since 1.25
165
	 */
166
	public static function parseAndStash( WikiPage $page, Content $content, User $user, $summary ) {
167
		$cache = ObjectCache::getLocalClusterInstance();
168
		$logger = LoggerFactory::getInstance( 'StashEdit' );
169
170
		$title = $page->getTitle();
171
		$key = self::getStashKey( $title, self::getContentHash( $content ), $user );
172
173
		// Use the master DB for fast blocking locks
174
		$dbw = wfGetDB( DB_MASTER );
175
		if ( !$dbw->lock( $key, __METHOD__, 1 ) ) {
176
			// De-duplicate requests on the same key
177
			return self::ERROR_BUSY;
178
		}
179
		/** @noinspection PhpUnusedLocalVariableInspection */
180
		$unlocker = new ScopedCallback( function () use ( $dbw, $key ) {
181
			$dbw->unlock( $key, __METHOD__ );
182
		} );
183
184
		$cutoffTime = time() - self::PRESUME_FRESH_TTL_SEC;
185
186
		// Reuse any freshly build matching edit stash cache
187
		$editInfo = $cache->get( $key );
188
		if ( $editInfo && wfTimestamp( TS_UNIX, $editInfo->timestamp ) >= $cutoffTime ) {
189
			$alreadyCached = true;
190
		} else {
191
			$format = $content->getDefaultFormat();
192
			$editInfo = $page->prepareContentForEdit( $content, null, $user, $format, false );
193
			$alreadyCached = false;
194
		}
195
196
		if ( $editInfo && $editInfo->output ) {
197
			// Let extensions add ParserOutput metadata or warm other caches
198
			Hooks::run( 'ParserOutputStashForEdit',
199
				[ $page, $content, $editInfo->output, $summary, $user ] );
200
201
			if ( $alreadyCached ) {
202
				$logger->debug( "Already cached parser output for key '$key' ('$title')." );
203
				return self::ERROR_NONE;
204
			}
205
206
			list( $stashInfo, $ttl, $code ) = self::buildStashValue(
207
				$editInfo->pstContent,
208
				$editInfo->output,
209
				$editInfo->timestamp,
210
				$user
211
			);
212
213
			if ( $stashInfo ) {
214
				$ok = $cache->set( $key, $stashInfo, $ttl );
215
				if ( $ok ) {
216
					$logger->debug( "Cached parser output for key '$key' ('$title')." );
217
					return self::ERROR_NONE;
218
				} else {
219
					$logger->error( "Failed to cache parser output for key '$key' ('$title')." );
220
					return self::ERROR_CACHE;
221
				}
222
			} else {
223
				$logger->info( "Uncacheable parser output for key '$key' ('$title') [$code]." );
224
				return self::ERROR_UNCACHEABLE;
225
			}
226
		}
227
228
		return self::ERROR_PARSE;
229
	}
230
231
	/**
232
	 * Check that a prepared edit is in cache and still up-to-date
233
	 *
234
	 * This method blocks if the prepared edit is already being rendered,
235
	 * waiting until rendering finishes before doing final validity checks.
236
	 *
237
	 * The cache is rejected if template or file changes are detected.
238
	 * Note that foreign template or file transclusions are not checked.
239
	 *
240
	 * The result is a map (pstContent,output,timestamp) with fields
241
	 * extracted directly from WikiPage::prepareContentForEdit().
242
	 *
243
	 * @param Title $title
244
	 * @param Content $content
245
	 * @param User $user User to get parser options from
246
	 * @return stdClass|bool Returns false on cache miss
247
	 */
248
	public static function checkCache( Title $title, Content $content, User $user ) {
249
		if ( $user->isBot() ) {
250
			return false; // bots never stash - don't pollute stats
251
		}
252
253
		$cache = ObjectCache::getLocalClusterInstance();
254
		$logger = LoggerFactory::getInstance( 'StashEdit' );
255
		$stats = MediaWikiServices::getInstance()->getStatsdDataFactory();
256
257
		$key = self::getStashKey( $title, self::getContentHash( $content ), $user );
258
		$editInfo = $cache->get( $key );
259
		if ( !is_object( $editInfo ) ) {
260
			$start = microtime( true );
261
			// We ignore user aborts and keep parsing. Block on any prior parsing
262
			// so as to use its results and make use of the time spent parsing.
263
			// Skip this logic if there no master connection in case this method
264
			// is called on an HTTP GET request for some reason.
265
			$lb = MediaWikiServices::getInstance()->getDBLoadBalancer();
266
			$dbw = $lb->getAnyOpenConnection( $lb->getWriterIndex() );
267
			if ( $dbw && $dbw->lock( $key, __METHOD__, 30 ) ) {
268
				$editInfo = $cache->get( $key );
269
				$dbw->unlock( $key, __METHOD__ );
270
			}
271
272
			$timeMs = 1000 * max( 0, microtime( true ) - $start );
273
			$stats->timing( 'editstash.lock_wait_time', $timeMs );
274
		}
275
276
		if ( !is_object( $editInfo ) || !$editInfo->output ) {
277
			$stats->increment( 'editstash.cache_misses.no_stash' );
278
			$logger->debug( "Empty cache for key '$key' ('$title'); user '{$user->getName()}'." );
279
			return false;
280
		}
281
282
		$age = time() - wfTimestamp( TS_UNIX, $editInfo->output->getCacheTime() );
283
		if ( $age <= self::PRESUME_FRESH_TTL_SEC ) {
284
			// Assume nothing changed in this time
285
			$stats->increment( 'editstash.cache_hits.presumed_fresh' );
286
			$logger->debug( "Timestamp-based cache hit for key '$key' (age: $age sec)." );
287
		} elseif ( isset( $editInfo->edits ) && $editInfo->edits === $user->getEditCount() ) {
288
			// Logged-in user made no local upload/template edits in the meantime
289
			$stats->increment( 'editstash.cache_hits.presumed_fresh' );
290
			$logger->debug( "Edit count based cache hit for key '$key' (age: $age sec)." );
291
		} elseif ( $user->isAnon()
292
			&& self::lastEditTime( $user ) < $editInfo->output->getCacheTime()
293
		) {
294
			// Logged-out user made no local upload/template edits in the meantime
295
			$stats->increment( 'editstash.cache_hits.presumed_fresh' );
296
			$logger->debug( "Edit check based cache hit for key '$key' (age: $age sec)." );
297
		} else {
298
			// User may have changed included content
299
			$editInfo = false;
300
		}
301
302
		if ( !$editInfo ) {
303
			$stats->increment( 'editstash.cache_misses.proven_stale' );
304
			$logger->info( "Stale cache for key '$key'; old key with outside edits. (age: $age sec)" );
305
		} elseif ( $editInfo->output->getFlag( 'vary-revision' ) ) {
306
			// This can be used for the initial parse, e.g. for filters or doEditContent(),
307
			// but a second parse will be triggered in doEditUpdates(). This is not optimal.
308
			$logger->info( "Cache for key '$key' ('$title') has vary_revision." );
309
		} elseif ( $editInfo->output->getFlag( 'vary-revision-id' ) ) {
310
			// Similar to the above if we didn't guess the ID correctly.
311
			$logger->info( "Cache for key '$key' ('$title') has vary_revision_id." );
312
		}
313
314
		return $editInfo;
315
	}
316
317
	/**
318
	 * @param User $user
319
	 * @return string|null TS_MW timestamp or null
320
	 */
321
	private static function lastEditTime( User $user ) {
322
		$time = wfGetDB( DB_REPLICA )->selectField(
323
			'recentchanges',
324
			'MAX(rc_timestamp)',
325
			[ 'rc_user_text' => $user->getName() ],
326
			__METHOD__
327
		);
328
329
		return wfTimestampOrNull( TS_MW, $time );
330
	}
331
332
	/**
333
	 * Get hash of the content, factoring in model/format
334
	 *
335
	 * @param Content $content
336
	 * @return string
337
	 */
338
	private static function getContentHash( Content $content ) {
339
		return sha1( implode( "\n", [
340
			$content->getModel(),
341
			$content->getDefaultFormat(),
342
			$content->serialize( $content->getDefaultFormat() )
343
		] ) );
344
	}
345
346
	/**
347
	 * Get the temporary prepared edit stash key for a user
348
	 *
349
	 * This key can be used for caching prepared edits provided:
350
	 *   - a) The $user was used for PST options
351
	 *   - b) The parser output was made from the PST using cannonical matching options
352
	 *
353
	 * @param Title $title
354
	 * @param string $contentHash Result of getContentHash()
355
	 * @param User $user User to get parser options from
356
	 * @return string
357
	 */
358
	private static function getStashKey( Title $title, $contentHash, User $user ) {
359
		return ObjectCache::getLocalClusterInstance()->makeKey(
360
			'prepared-edit',
361
			md5( $title->getPrefixedDBkey() ),
362
			// Account for the edit model/text
363
			$contentHash,
364
			// Account for user name related variables like signatures
365
			md5( $user->getId() . "\n" . $user->getName() )
366
		);
367
	}
368
369
	/**
370
	 * Build a value to store in memcached based on the PST content and parser output
371
	 *
372
	 * This makes a simple version of WikiPage::prepareContentForEdit() as stash info
373
	 *
374
	 * @param Content $pstContent Pre-Save transformed content
375
	 * @param ParserOutput $parserOutput
376
	 * @param string $timestamp TS_MW
377
	 * @param User $user
378
	 * @return array (stash info array, TTL in seconds, info code) or (null, 0, info code)
379
	 */
380
	private static function buildStashValue(
381
		Content $pstContent, ParserOutput $parserOutput, $timestamp, User $user
382
	) {
383
		// If an item is renewed, mind the cache TTL determined by config and parser functions.
384
		// Put an upper limit on the TTL for sanity to avoid extreme template/file staleness.
385
		$since = time() - wfTimestamp( TS_UNIX, $parserOutput->getTimestamp() );
386
		$ttl = min( $parserOutput->getCacheExpiry() - $since, self::MAX_CACHE_TTL );
387
		if ( $ttl <= 0 ) {
388
			return [ null, 0, 'no_ttl' ];
389
		}
390
391
		// Only store what is actually needed
392
		$stashInfo = (object)[
393
			'pstContent' => $pstContent,
394
			'output'     => $parserOutput,
395
			'timestamp'  => $timestamp,
396
			'edits'      => $user->getEditCount()
397
		];
398
399
		return [ $stashInfo, $ttl, 'ok' ];
400
	}
401
402
	public function getAllowedParams() {
403
		return [
404
			'title' => [
405
				ApiBase::PARAM_TYPE => 'string',
406
				ApiBase::PARAM_REQUIRED => true
407
			],
408
			'section' => [
409
				ApiBase::PARAM_TYPE => 'string',
410
			],
411
			'sectiontitle' => [
412
				ApiBase::PARAM_TYPE => 'string'
413
			],
414
			'text' => [
415
				ApiBase::PARAM_TYPE => 'text',
416
				ApiBase::PARAM_DFLT => null
417
			],
418
			'stashedtexthash' => [
419
				ApiBase::PARAM_TYPE => 'string',
420
				ApiBase::PARAM_DFLT => null
421
			],
422
			'summary' => [
423
				ApiBase::PARAM_TYPE => 'string',
424
			],
425
			'contentmodel' => [
426
				ApiBase::PARAM_TYPE => ContentHandler::getContentModels(),
427
				ApiBase::PARAM_REQUIRED => true
428
			],
429
			'contentformat' => [
430
				ApiBase::PARAM_TYPE => ContentHandler::getAllContentFormats(),
431
				ApiBase::PARAM_REQUIRED => true
432
			],
433
			'baserevid' => [
434
				ApiBase::PARAM_TYPE => 'integer',
435
				ApiBase::PARAM_REQUIRED => true
436
			]
437
		];
438
	}
439
440
	public function needsToken() {
441
		return 'csrf';
442
	}
443
444
	public function mustBePosted() {
445
		return true;
446
	}
447
448
	public function isWriteMode() {
449
		return true;
450
	}
451
452
	public function isInternal() {
453
		return true;
454
	}
455
}
456