Hard deprecate Preprocessor_DOM

The Preprocessor_DOM implementation doesn't interact well with PHP memory
profiling, and has some limitations not present in the Preprocessor_Hash
implementation (see T216664).  There is no reason to keep around two
versions of the preprocessor: it just complicates on-going wikitext
feature development.

Hard deprecate use of Preprocessor_DOM, so we can remove the redundant
code in a future release.

Bug: T204945
Depends-On: Id38c9360e4d02b570996dbf7a660f964f02f1a2c
Change-Id: Ica5d1ad5b1e677542962fc36d582a793f941155e

10 files changed, 23 insertions, 12 deletions

diff --git a/RELEASE-NOTES-1.34 b/RELEASE-NOTES-1.34
index cc1015c824c5..5917e3ce53bc 100644
--- a/RELEASE-NOTES-1.34
+++ b/RELEASE-NOTES-1.34
@@ -265,6 +265,9 @@ because of Phabricator reports.
 * ResourceLoaderContext::getConfig and ResourceLoaderContext::getLogger have
   been deprecated. Inside ResourceLoaderModule subclasses, use the local methods
   instead. Elsewhere, use the methods from the ResourceLoader class.
+* The Preprocessor_DOM implementation has been deprecated.  It will be
+  removed in a future release.  Use the Preprocessor_Hash implementation
+  instead.
 
 === Other changes in 1.34 ===
 * …
diff --git a/includes/DefaultSettings.php b/includes/DefaultSettings.php
index 1be573d030f0..7d6318d2068e 100644
--- a/includes/DefaultSettings.php
+++ b/includes/DefaultSettings.php
@@ -4153,6 +4153,9 @@ $wgInvalidRedirectTargets = [ 'Filepath', 'Mypage', 'Mytalk', 'Redirect' ];
  *                    If this parameter is not given, it uses Preprocessor_DOM if the
  *                    DOM module is available, otherwise it uses Preprocessor_Hash.
  *
+ * The Preprocessor_DOM class is deprecated, and will be removed in a future
+ * release.
+ *
  * The entire associative array will be passed through to the constructor as
  * the first parameter. Note that only Setup.php can use this variable --
  * the configuration will change at runtime via Parser member functions, so
diff --git a/includes/parser/PPCustomFrame_DOM.php b/includes/parser/PPCustomFrame_DOM.php
index 70663a0deaed..d274558afc0e 100644
--- a/includes/parser/PPCustomFrame_DOM.php
+++ b/includes/parser/PPCustomFrame_DOM.php
@@ -21,6 +21,7 @@
 
 /**
  * Expansion frame with custom arguments
+ * @deprecated since 1.34, use PPCustomFrame_Hash
  * @ingroup Parser
  */
 // phpcs:ignore Squiz.Classes.ValidClassName.NotCamelCaps
diff --git a/includes/parser/PPFrame_DOM.php b/includes/parser/PPFrame_DOM.php
index a7fea0028aa9..03ee6d963963 100644
--- a/includes/parser/PPFrame_DOM.php
+++ b/includes/parser/PPFrame_DOM.php
@@ -21,6 +21,7 @@
 
 /**
  * An expansion frame, used as a context to expand the result of preprocessToObj()
+ * @deprecated since 1.34, use PPFrame_Hash
  * @ingroup Parser
  */
 // phpcs:ignore Squiz.Classes.ValidClassName.NotCamelCaps
diff --git a/includes/parser/PPNode_DOM.php b/includes/parser/PPNode_DOM.php
index 8a435bab67a9..26a47911f335 100644
--- a/includes/parser/PPNode_DOM.php
+++ b/includes/parser/PPNode_DOM.php
@@ -20,6 +20,7 @@
  */
 
 /**
+ * @deprecated since 1.34, use PPNode_Hash_{Tree,Text,Array,Attr}
  * @ingroup Parser
  */
 // phpcs:ignore Squiz.Classes.ValidClassName.NotCamelCaps
diff --git a/includes/parser/PPTemplateFrame_DOM.php b/includes/parser/PPTemplateFrame_DOM.php
index 52cb9cb0f0b8..b4c874371d41 100644
--- a/includes/parser/PPTemplateFrame_DOM.php
+++ b/includes/parser/PPTemplateFrame_DOM.php
@@ -21,6 +21,7 @@
 
 /**
  * Expansion frame with template arguments
+ * @deprecated since 1.34, use PPTemplateFrame_Hash
  * @ingroup Parser
  */
 // phpcs:ignore Squiz.Classes.ValidClassName.NotCamelCaps
diff --git a/includes/parser/Parser.php b/includes/parser/Parser.php
index 486fdf441367..c61de38a867c 100644
--- a/includes/parser/Parser.php
+++ b/includes/parser/Parser.php
@@ -421,21 +421,10 @@ class Parser {
 	 * Which class should we use for the preprocessor if not otherwise specified?
 	 *
 	 * @since 1.34
+	 * @deprecated since 1.34, removing configurability of preprocessor
 	 * @return string
 	 */
 	public static function getDefaultPreprocessorClass() {
-		if ( wfIsHHVM() ) {
-			# Under HHVM Preprocessor_Hash is much faster than Preprocessor_DOM
-			return Preprocessor_Hash::class;
-		}
-		if ( extension_loaded( 'domxml' ) ) {
-			# PECL extension that conflicts with the core DOM extension (T15770)
-			wfDebug( "Warning: you have the obsolete domxml extension for PHP. Please remove it!\n" );
-			return Preprocessor_Hash::class;
-		}
-		if ( extension_loaded( 'dom' ) ) {
-			return Preprocessor_DOM::class;
-		}
 		return Preprocessor_Hash::class;
 	}
 
diff --git a/includes/parser/Preprocessor_DOM.php b/includes/parser/Preprocessor_DOM.php
index 0f0496beac15..9e510d21d64b 100644
--- a/includes/parser/Preprocessor_DOM.php
+++ b/includes/parser/Preprocessor_DOM.php
@@ -19,6 +19,7 @@
  *
  * @file
  * @ingroup Parser
+ * @deprecated since 1.34, use Preprocessor_Hash
  */
 
 /**
@@ -37,6 +38,7 @@ class Preprocessor_DOM extends Preprocessor {
 	const CACHE_PREFIX = 'preprocess-xml';
 
 	public function __construct( $parser ) {
+		wfDeprecated( __METHOD__, '1.34' ); // T204945
 		$this->parser = $parser;
 		$mem = ini_get( 'memory_limit' );
 		$this->memoryLimit = false;
diff --git a/tests/parser/ParserTestRunner.php b/tests/parser/ParserTestRunner.php
index 3b63c19a94e8..7d46e834c147 100644
--- a/tests/parser/ParserTestRunner.php
+++ b/tests/parser/ParserTestRunner.php
@@ -797,6 +797,13 @@ class ParserTestRunner {
 
 		$class = $wgParserConf['class'];
 		$parser = new $class( [ 'preprocessorClass' => $preprocessor ] + $wgParserConf );
+		if ( $preprocessor ) {
+			# Suppress deprecation warning for Preprocessor_DOM while testing
+			Wikimedia\suppressWarnings();
+			wfDeprecated( 'Preprocessor_DOM::__construct' );
+			Wikimedia\restoreWarnings();
+			$parser->getPreprocessor();
+		}
 		ParserTestParserHook::setup( $parser );
 
 		return $parser;
diff --git a/tests/phpunit/includes/parser/PreprocessorTest.php b/tests/phpunit/includes/parser/PreprocessorTest.php
index 6b3e05da513f..3b2b1050bd17 100644
--- a/tests/phpunit/includes/parser/PreprocessorTest.php
+++ b/tests/phpunit/includes/parser/PreprocessorTest.php
@@ -48,6 +48,9 @@ class PreprocessorTest extends MediaWikiTestCase {
 		$this->mOptions = ParserOptions::newFromUserAndLang( new User,
 			MediaWikiServices::getInstance()->getContentLanguage() );
 
+		# Suppress deprecation warning for Preprocessor_DOM while testing
+		$this->hideDeprecated( 'Preprocessor_DOM::__construct' );
+
 		$this->mPreprocessors = [];
 		foreach ( self::$classNames as $className ) {
 			$this->mPreprocessors[$className] = new $className( $this );