First-pass cleanup:

* Removed ScriptingEngineBase::load(), inappropriate interface specification, only used by child classes and more properly defined by them
* Fixed inappropriate use of final
* Fixed case of a class constant to conform with MediaWiki conventions
* Use a factory function interface for module creation instead of a class name accessor
* Don't pass unnecessary $engine parameter to ScriptingFunctionBase::__construct(). Pass parent object as the first parameter per convention.
* Fixed unnecessary reference parameter in doRunHook()
* Have LuaSandboxEngineFunction::call() return the first result or null, per the base class documentation, instead of imploding. 
* Use strval() to avoid a warning in case call() returns an array or object
* Improved some comments

common/Base.php

@@ -3,7 +3,6 @@
 /**
  * Wikitext scripting infrastructure for MediaWiki: base classes.
  * Copyright (C) 2012 Victor Vasiliev <vasilvv@gmail.com> et al
- * Based on MediaWiki file LinksUpdate.php
  * http://www.mediawiki.org/
  *
  * This program is free software; you can redistribute it and/or modify
@@ -31,19 +30,12 @@ abstract class ScriptingEngineBase {
 	protected
 		$mParser,
 		$mModules = array(),
-		$mModuleTitles = array(),
-		$mLoaded = false;
+		$mModuleTitles = array();
 
 	/**
-	 * Required for the lazy-loading of the engine. Should have a sentinel
-	 * inside checking whether it is already loaded.
+	 * Creates a new module object within this engine
 	 */
-	abstract public function load();
-
-	/**
-	 * Returns the name of your module class.
-	 */
-	abstract protected function getModuleClassName();
+	abstract protected function newModule( $title, $code, $revisionID, $source );
 
 	/**
 	 * Returns the default options of the engine.
@@ -61,7 +53,7 @@ abstract class ScriptingEngineBase {
 	 * 
 	 * @param $parser Parser Wikitext parser
 	 */
-	public final function __construct( $parser ) {
+	public function __construct( $parser ) {
 		$this->mParser = $parser;
 	}
 
@@ -74,7 +66,7 @@ abstract class ScriptingEngineBase {
 	 * @param $source string Source of the module
 	 * @return ScriptingEngineModule
 	 */
-	public function getModule( $title, $source = Scripting::Local ) {
+	public function getModule( $title, $source = Scripting::LOCAL ) {
 		// Convert string to title
 		if( !$title instanceof Title ) {
 			$titleobj = Title::newFromText( (string)$title, NS_MODULE );
@@ -97,8 +89,7 @@ abstract class ScriptingEngineBase {
 			}
 
 			// Create the class
-			$class = $this->getModuleClassName();
-			$this->mModules[$key] = new $class( $this, $title, $rev->getText(), $rev->getID(), $source );
+			$this->mModules[$key] = $this->newModule( $title, $rev->getText(), $rev->getID(), $source );
 			$this->mModuleTitles[] = $title;
 		}
 		return $this->mModules[$key];
@@ -108,7 +99,7 @@ abstract class ScriptingEngineBase {
 	 * Fetches the revision for given module title.
 	 */
 	private function getModuleRev( $title, $source ) {
-		if( $source != Scripting::Local ) {
+		if( $source != Scripting::LOCAL ) {
 			throw new MWException( 'Non-local scripts are not supported at this point' );
 		}
 
@@ -128,7 +119,7 @@ abstract class ScriptingEngineBase {
 	}
 
 	/**
-	 * Validates the script and returns an array of the syntax erros for the
+	 * Validates the script and returns an array of the syntax errors for the
 	 * given code.
 	 * 
 	 * @param $code Code to validate
@@ -136,8 +127,7 @@ abstract class ScriptingEngineBase {
 	 * @return array
 	 */
 	function validate( $code, $title ) {
-		$class = $this->getModuleClassName();
-		$module = new $class( $this, $title, $code, 0, Scripting::Local );
+		$module = $this->newModule( $title, $code, 0, Scripting::LOCAL );
 
 		try {
 			$module->initialize();
@@ -195,7 +185,7 @@ abstract class ScriptingEngineBase {
 abstract class ScriptingModuleBase {
 	var $mEngine, $mTitle, $mCode, $mRevisionID, $mSource;
 
-	public final function __construct( $engine, $title, $code, $revisionID, $source ) {
+	public function __construct( $engine, $title, $code, $revisionID, $source ) {
 		$this->mEngine = $engine;
 		$this->mTitle = $title;
 		$this->mCode = $code;
@@ -236,11 +226,11 @@ abstract class ScriptingModuleBase {
 abstract class ScriptingFunctionBase {
 	protected $mName, $mContents, $mModule, $mEngine;
 	
-	public final function __construct( $name, $contents, $module, $engine ) {
+	public function __construct( $module, $name, $contents ) {
 		$this->mName = $name;
 		$this->mContents = $contents;
 		$this->mModule = $module;
-		$this->mEngine = $engine;
+		$this->mEngine = $module->getEngine();
 	}
 	
 	/**

common/Common.php

@@ -4,7 +4,7 @@
  * Generic scripting functions.
  */
 class Scripting {
-	const Local = 'local';
+	const LOCAL = 'local';
 
 	protected static function getEngineClass() {
 		global $wgScriptingEngine, $wgScriptingEngines;

common/Hooks.php

@@ -21,7 +21,7 @@
  */
 
 /**
- * Hooks for Scripting extension.
+ * Hooks for the Scripting extension.
  */
 class ScriptingHooks {
 	/**
@@ -35,7 +35,7 @@ class ScriptingHooks {
 	}
 
 	/**
-	 * Called when interpreter is to be reset.
+	 * Called when the interpreter is to be reset.
 	 * 
 	 * @static
 	 * @param  $parser Parser
@@ -47,7 +47,7 @@ class ScriptingHooks {
 	}
 
 	/**
-	 * Adds scriptlinks table to parser tests.
+	 * Add scriptlinks table to parser tests.
 	 */
 	public static function addTestTables( &$tables ) {
 		$tables[] = 'scriptlinks';
@@ -55,7 +55,7 @@ class ScriptingHooks {
 	}
 
 	/**
-	 * Handles the {{#invoke:module|func}} construction.
+	 * Hook function for {{#invoke:module|func}}
 	 *
 	 * @param $parser Parser
 	 * @param $frame PPFrame
@@ -73,7 +73,7 @@ class ScriptingHooks {
 	}
 
 	/**
-	 * Handles the transclusion of the script ({{script:module}} hook).
+	 * Hook function for {{script:module}}
 	 *
 	 * @param $parser Parser
 	 * @param $frame PPFrame
@@ -94,7 +94,7 @@ class ScriptingHooks {
 	 * @return string
 	 * @throws ScriptingException
 	 */
-	private static function doRunHook( &$parser, $frame, $module, $function, $args ) {
+	private static function doRunHook( $parser, $frame, $module, $function, $args ) {
 		wfProfileIn( __METHOD__ );
 
 		try {
@@ -104,7 +104,7 @@ class ScriptingHooks {
 				$arg = $frame->expand( $arg );
 			}
 
-			$module = $engine->getModule( $module, Scripting::Local );
+			$module = $engine->getModule( $module, Scripting::LOCAL );
 
 			$functionObj = $module->getFunction( $function );
 			if( !$functionObj ) {
@@ -114,7 +114,7 @@ class ScriptingHooks {
 			$result = $functionObj->call( $args, $frame );
 
 			wfProfileOut( __METHOD__ );
-			return trim( $result );
+			return trim( strval( $result ) );
 		} catch( ScriptingException $e ) {
 			$msg = $e->getMessage();
 			wfProfileOut( __METHOD__ );

common/LinkUpdates.php

@@ -31,7 +31,7 @@ if( !defined( 'MEDIAWIKI' ) )
  */
 class ScriptLinksUpdateHooks {
 	/**
-	 * Appends script links to the output.
+	 * Append script links to the output.
 	 */
 	public static function appendToOutput( &$parser, &$text ) {
 		if( isset( $parser->scripting_engine ) ) {
@@ -41,7 +41,7 @@ class ScriptLinksUpdateHooks {
 	}
 
 	/**
-	 * Runs the link updater.
+	 * Run the link updater.
 	 */
 	public static function updateLinks( &$update ) {
 		$output = $update->mParserOutput;
@@ -57,7 +57,7 @@ class ScriptLinksUpdateHooks {
 	}
 
 	/**
-	 * Purges cache for all the pages where the script is used.
+	 * Purge cache for all the pages where the script is used.
 	 * @param $article Article
 	 * @param $editInfo
 	 * @param $changed
@@ -71,7 +71,7 @@ class ScriptLinksUpdateHooks {
 			$engine = Scripting::getEngine( $wgParser );
 			$engine->invalidateModuleCache( $article->getTitle() );
 			
-			// Invalidate caches of articles which include the script
+			// Invalidate the caches of articles which include the script
 			$wgDeferredUpdateList[] = new HTMLCacheUpdate( $article->getTitle(), 'scriptlinks' );
 		}
 
@@ -79,7 +79,7 @@ class ScriptLinksUpdateHooks {
 	}
 
 	/**
-	 * Adds scriptlinks to the list of tables supported by BacklinkCache.
+	 * Add scriptlinks to the list of tables supported by BacklinkCache.
 	 */
 	public static function getBacklinkCachePrefix( $table, &$prefix ) {
 		if( $table == 'scriptlinks' ) {
@@ -91,7 +91,7 @@ class ScriptLinksUpdateHooks {
 	}
 
 	/**
-	 * Adds scriptlinks to the list of tables supported by BacklinkCache.
+	 * Add scriptlinks to the list of tables supported by BacklinkCache.
 	 * @param $table
 	 * @param $title Title
 	 * @param $conds
@@ -111,7 +111,7 @@ class ScriptLinksUpdateHooks {
 }
 
 /**
- * A class that updates links on scripts like phase3/includes/LinksUpdate.php does that
+ * A class that updates links on scripts like what phase3/includes/LinksUpdate.php does
  * with templates.
  */
 class ScriptLinksUpdate {

engines/LuaSandbox/Engine.php

@@ -1,7 +1,11 @@
 <?php
 
 class LuaSandboxEngine extends ScriptingEngineBase {
-	public $mSandbox;
+	public $mSandbox, $mLoaded = false;
+
+	public function newModule( $title, $code, $revisionID, $source ) {
+		return new LuaSandboxEngineModule( $this, $title, $code, $revisionID, $source );
+	}
 
 	public function load() {
 		if( $this->mLoaded ) {
@@ -119,7 +123,7 @@ class LuaSandboxEngineModule extends ScriptingModuleBase {
 		$this->initialize();
 
 		if( isset( $this->mContents[$name] ) ) {
-			return new LuaSandboxEngineFunction( $name, $this->mContents[$name], $this, $this->mEngine );
+			return new LuaSandboxEngineFunction( $this, $name, $this->mContents[$name] );
 		} else {
 			return null;
 		}
@@ -139,6 +143,10 @@ class LuaSandboxEngineFunction extends ScriptingFunctionBase {
 			throw new ScriptingException( 'error', 'luasandbox', null, null, array( $e->getMessage() ) );
 		}
 		
-		return implode( '', $result );
+		if ( isset( $result[0] ) ) {
+			return $result[0];
+		} else {
+			return null;
+		}
 	}
 }