(bug 45774) Add title.fileExists, improve title.exists

People sometimes want to know if the actual file exists, not just the
file description page. Support that.

Also alias .exists to .fileExists for the Media namespace, since that's
what the Media namespace is for.

And while we're at it, fix .exists for special pages too.

Bug: 45774
Change-Id: I019adc89858a1d32995a38d5e8eef32577fd32d6

engines/LuaCommon/TitleLibrary.php

@@ -14,9 +14,11 @@ class Scribunto_LuaTitleLibrary extends Scribunto_LuaLibraryBase {
 			'makeTitle' => array( $this, 'makeTitle' ),
 			'getUrl' => array( $this, 'getUrl' ),
 			'getContent' => array( $this, 'getContent' ),
+			'fileExists' => array( $this, 'fileExists' ),
 		);
 		$this->getEngine()->registerInterface( 'mw.title.lua', $lib, array(
 			'thisTitle' => $this->returnTitleToLua( $this->getTitle() ),
+			'NS_MEDIA' => NS_MEDIA,
 		) );
 	}
 
@@ -69,11 +71,12 @@ class Scribunto_LuaTitleLibrary extends Scribunto_LuaLibraryBase {
 			$this->getParser()->getOutput()->addLink( $title );
 		}
 
-		return array(
+		$ns = $title->getNamespace();
+		$ret = array(
 			'isLocal' => (bool)$title->isLocal(),
 			'isRedirect' => (bool)$title->isRedirect(),
 			'interwiki' => $title->getInterwiki(),
-			'namespace' => $title->getNamespace(),
+			'namespace' => $ns,
 			'nsText' => $title->getNsText(),
 			'text' => $title->getText(),
 			'id' => $title->getArticleID(),
@@ -81,6 +84,15 @@ class Scribunto_LuaTitleLibrary extends Scribunto_LuaLibraryBase {
 			'contentModel' => $title->getContentModel(),
 			'thePartialUrl' => $title->getPartialURL(),
 		);
+		if ( $ns === NS_SPECIAL ) {
+			$ret['exists'] = (bool)SpecialPageFactory::exists( $title->getDBkey() );
+		} else {
+			$ret['exists'] = $ret['id'] > 0;
+		}
+		if ( $ns !== NS_FILE && $ns !== NS_MEDIA ) {
+			$ret['fileExists'] = false;
+		}
+		return $ret;
 	}
 
 	/**
@@ -198,6 +210,7 @@ class Scribunto_LuaTitleLibrary extends Scribunto_LuaLibraryBase {
 	}
 
 	function getContent( $text ) {
+		$this->checkType( 'getContent', 1, $text, 'string' );
 		$title = Title::newFromText( $text );
 		if ( !$title ) {
 			return array( null );
@@ -218,4 +231,26 @@ class Scribunto_LuaTitleLibrary extends Scribunto_LuaLibraryBase {
 		}
 		return array( $content->serialize() );
 	}
+
+	function fileExists( $text ) {
+		$this->checkType( 'fileExists', 1, $text, 'string' );
+		$title = Title::newFromText( $text );
+		if ( !$title ) {
+			return array( false );
+		}
+		$ns = $title->getNamespace();
+		if ( $ns !== NS_FILE && $ns !== NS_MEDIA ) {
+			return array( false );
+		}
+
+		$this->incrementExpensiveFunctionCount();
+		$file = wfFindFile( $title );
+		if ( !$file ) {
+			return array( false );
+		}
+		$this->getParser()->getOutput()->addImage(
+			$file->getName(), $file->getTimestamp(), $file->getSha1()
+		);
+		return array( (bool)$file->exists() );
+	}
 }

engines/LuaCommon/lualib/mw.title.lua

@@ -1,5 +1,6 @@
 local title = {}
 local php
+local NS_MEDIA = -2
 
 local util = require 'libraryUtil'
 local checkType = util.checkType
@@ -59,7 +60,6 @@ local function makeTitleObject( data )
 	data.isExternal = data.interwiki ~= ''
 	data.isSpecialPage = data.namespace == mw.site.namespaces.Special.id
 	data.isTalkPage = ns.isTalk
-	data.exists = data.id ~= 0
 	data.subjectNsText = ns.subject.name
 	data.canTalk = ns.talk ~= nil
 
@@ -154,10 +154,28 @@ local function makeTitleObject( data )
 		return content
 	end
 
+	-- Read-only fields, both those defined above and any dynamically handled
+	-- in __index.
+	local readOnlyFields = {
+		fullText = true,
+		rootPageTitle = true,
+		basePageTitle = true,
+		talkPageTitle = true,
+		subjectPageTitle = true,
+		fileExists = true,
+	}
+	for k in pairs( data ) do
+		readOnlyFields[k] = true
+	end
+
 	return setmetatable( obj, {
 		__eq = title.equals,
 		__lt = lt,
 		__index = function ( t, k )
+			if k == 'exists' and data.namespace == NS_MEDIA then
+				k = 'fileExists'
+			end
+
 			if k == 'fullText' then
 				if data.fragment ~= '' then
 					return data.prefixedText .. '#' .. data.fragment
@@ -189,6 +207,12 @@ local function makeTitleObject( data )
 				end
 				return title.makeTitle( ns.id, data.text )
 			end
+			if k == 'fileExists' then
+				if data.fileExists == nil then
+					data.fileExists = php.fileExists( data.prefixedText )
+				end
+				return data.fileExists
+			end
 
 			return data[k]
 		end,
@@ -196,7 +220,7 @@ local function makeTitleObject( data )
 			if k == 'fragment' then
 				checkTypeForIndex( k, v, 'string' )
 				data[k] = v
-			elseif data[k] then
+			elseif readOnlyFields[k] then
 				error( "index '" .. k .. "' is read only", 2 )
 			else
 				rawset( t, k, v )
@@ -213,6 +237,7 @@ function title.setupInterface( options )
 	title.setupInterface = nil
 	php = mw_interface
 	mw_interface = nil
+	NS_MEDIA = options.NS_MEDIA
 
 	-- Set current title
 	title.getCurrentTitle = function ()