Expose PPFrame::getTitle to Lua

This field already exists in PHP with exactly the content requested in
bug 47089, so we may as well expose it on the frame object.

Bug: 47089
Change-Id: I672820589f6ebc7c4daad29b5eb156733a5bc5cc

engines/LuaCommon/LuaCommon.php

@@ -81,6 +81,7 @@ abstract class Scribunto_LuaEngine extends ScribuntoEngineBase {
 				'preprocess',
 				'incrementExpensiveFunctionCount',
 				'isSubsting',
+				'getFrameTitle',
 			);
 
 			$lib = array();
@@ -401,6 +402,14 @@ abstract class Scribunto_LuaEngine extends ScribuntoEngineBase {
 		return array( $newFrameId );
 	}
 
+	/**
+	 * Handler for getTitle()
+	 */
+	function getFrameTitle( $frameId ) {
+		$frame = $this->getFrameById( $frameId );
+		return array( $frame->getTitle()->getPrefixedText() );
+	}
+
 	/**
 	 * Handler for getExpandedArgument()
 	 */

engines/LuaCommon/lualib/mw.lua

@@ -536,6 +536,11 @@ local function newFrame( frameId, ... )
 			)
 	end
 
+	function frame:getTitle()
+		checkSelf( self, 'getTitle' )
+		return php.getFrameTitle( frameId )
+	end
+
 	-- For backwards compat
 	function frame:argumentPairs()
 		checkSelf( self, 'argumentPairs' )

tests/engines/LuaCommon/luaParserTests.txt

@@ -137,6 +137,10 @@ function p.isSubsting( frame )
 	return tostring( mw.isSubsting() )
 end
 
+function p.getFrameTitle( frame )
+	return frame:getTitle()
+end
+
 return p
 !! endarticle
 
@@ -385,3 +389,12 @@ Scribunto: isSubsting during normal parse
 <p>false
 </p>
 !! end
+
+!! test
+Scribunto: frame:getTitle
+!! input
+{{#invoke:test|getFrameTitle}}
+!! result
+<p>Module:Test
+</p>
+!! end