Provide MW_VERSION and deprecate fake global $wgVersion

$wgVersion is not a configuration variable, it should never be
changed at run-time.

While we've gone in the route of class constants for most constants,
this one will not benefit from class-autoloading since it needs to
be present from the very beginning.

MW_VERSION is named similarly as PHP_VERSION, and $wgVersion is
now soft-deprecated.

Bug: T212738
Change-Id: I04628de4152dd5c72646813e08ff35e422e265a4

RELEASE-NOTES-1.35

@@ -451,6 +451,7 @@ because of Phabricator reports.
   - getAllContentFormats
   - protected $handler (not need anymore)
   - cleanupHandlersCache (not need anymore)
+* (T212738) The $wgVersion global is deprecated; instead, use MW_VERSION.
 * $wgMemc is deprecated, use
   MediaWikiServices::getInstance()->getLocalServerObjectCache() instead.
 * ImagePage::getImageLimitsFromOptions() is deprecated. Use static function

includes/DefaultSettings.php

@@ -71,8 +71,9 @@ $wgConfigRegistry = [
 /**
  * MediaWiki version number
  * @since 1.2
+ * @deprecated since 1.35; use the MW_VERSION constant instead
  */
-$wgVersion = '1.35.0-alpha';
+$wgVersion = MW_VERSION;
 
 /**
  * Name of the site. It must be changed in LocalSettings.php

includes/Defines.php

@@ -29,6 +29,15 @@ use Wikimedia\Rdbms\IDatabase;
  * @defgroup Constants MediaWiki constants
  */
 
+/**
+ * The running version of MediaWiki.
+ *
+ * This replaces the the $wgVersion global found in earlier versions.
+ *
+ * @since 1.35
+ */
+define( 'MW_VERSION', '1.35.0-alpha' );
+
 # Obsolete aliases
 
 /** @{

includes/MediaWikiVersionFetcher.php

@@ -9,19 +9,19 @@
 class MediaWikiVersionFetcher {
 
 	/**
-	 * Returns the MediaWiki version, in the format used by MediaWiki's wgVersion global.
+	 * Get the MediaWiki version, extracted from the PHP source file where it is defined.
 	 *
 	 * @return string
 	 * @throws RuntimeException
 	 */
 	public function fetchVersion() {
-		$defaultSettings = file_get_contents( __DIR__ . '/DefaultSettings.php' );
+		$code = file_get_contents( __DIR__ . '/Defines.php' );
 
 		$matches = [];
-		preg_match( "/wgVersion = '([0-9a-zA-Z\.\-]+)';/", $defaultSettings, $matches );
+		preg_match( "/define\( 'MW_VERSION', '([0-9a-zA-Z\.\-]+)'/", $code, $matches );
 
 		if ( count( $matches ) !== 2 ) {
-			throw new RuntimeException( 'Could not extract the MediaWiki version from DefaultSettings.php' );
+			throw new RuntimeException( 'Could not extract the MediaWiki version from Defines.php' );
 		}
 
 		return $matches[1];

tests/phpunit/includes/MediaWikiVersionFetcherTest.php

@@ -13,9 +13,8 @@
 class MediaWikiVersionFetcherTest extends \MediaWikiIntegrationTestCase {
 
 	public function testReturnsResult() {
-		global $wgVersion;
 		$versionFetcher = new MediaWikiVersionFetcher();
-		$this->assertSame( $wgVersion, $versionFetcher->fetchVersion() );
+		$this->assertSame( MW_VERSION, $versionFetcher->fetchVersion() );
 	}
 
 }