Add unconvertable content to the result

There may be legacy Confluence WikiText contents included in the export,
which can not be converted by this tool. In this case, we just want to
add them as raw text to the result.

src/Converter/ConfluenceConverter.php

@@ -6,6 +6,7 @@
 use DOMElement;
 use DOMNode;
 use DOMXPath;
+use Exception;
 use HalloWelt\MediaWiki\Lib\Migration\Converter\PandocHTML;
 use HalloWelt\MediaWiki\Lib\Migration\DataBuckets;
 use HalloWelt\MediaWiki\Lib\Migration\IOutputAwareInterface;
@@ -167,7 +168,13 @@ protected function doConvert( SplFileInfo $file ): string {
 			$this->currentPageTitle = 'not_current_revision_' . $pageId;
 		}
 
-		$dom = $this->preprocessFile();
+		try {
+			$dom = $this->preprocessFile();
+		}
+		catch ( Exception $e ) {
+			$rawContent = file_get_contents( $this->rawFile->getPathname() );
+			return "<-- Unconvertable RAW start-->\n$rawContent\n<-- Unconvertable RAW start-->\n[[Category:Unconvertable]]";
+		}
 
 		$xpath = new DOMXPath( $dom );
 		$xpath->registerNamespace( 'ac', 'some' );
@@ -325,7 +332,10 @@ private function preprocessFile() {
 		$dom->formatOutput = true;
 		$dom->preserveWhiteSpace = true;
 		$dom->validateOnParse = false;
-		$dom->loadXML( $source, LIBXML_PARSEHUGE );
+		$validXML = $dom->loadXML( $source, LIBXML_PARSEHUGE );
+		if ( $validXML === false ) {
+			throw new Exception( 'Unconvertable');
+		}
 
 		$preprocessedPathname = str_replace( '.mraw', '.mprep', $this->rawFile->getPathname() );
 		$dom->saveHTMLFile( $preprocessedPathname );