Merge "Parser: Better debugging of lock errors ("Did you call Parser::parse recursive...

diff --combined includes/parser/Parser.php
index b3e37a4,11392de..34f6232
--- 1/includes/parser/Parser.php
--- 2/includes/parser/Parser.php
+++ b/includes/parser/Parser.php
@@@ -245,7 -245,7 +245,7 @@@ class Parser 
        public $currentRevisionCache;
  
        /**
-        * @var bool Recursive call protection.
+        * @var bool|string Recursive call protection.
         * This variable should be treated as if it were private.
         */
        public $mInParse = false;
@@@ -4400,6 -4400,7 +4400,6 @@@
                        $toc = Linker::tocList( $toc, $this->mOptions->getUserLangObj() );
                        $this->mOutput->setTOCHTML( $toc );
                        $toc = self::TOC_START . $toc . self::TOC_END;
 -                      $this->mOutput->addModules( 'mediawiki.toc' );
                }
  
                if ( $isMain ) {
@@@ -6072,9 -6073,13 +6072,13 @@@
        protected function lock() {
                if ( $this->mInParse ) {
                        throw new MWException( "Parser state cleared while parsing. "
-                               . "Did you call Parser::parse recursively?" );
+                               . "Did you call Parser::parse recursively? Lock is held by: " . $this->mInParse );
                }
-               $this->mInParse = true;
+ 
+               // Save the backtrace when locking, so that if some code tries locking again,
+               // we can print the lock owner's backtrace for easier debugging
+               $e = new Exception;
+               $this->mInParse = $e->getTraceAsString();
  
                $recursiveCheck = new ScopedCallback( function() {
                        $this->mInParse = false;