Fixed error handling of invalid XSL transformations

* xalan is segfaulting in XalanDOMString constructor when the static member "XalanLocator::getSystemId" is returning null-pointer
** this should seemingly be handled by passing a pointer to the static constant m_dummy but this sadly fails to prevent the segfault
** the patch provided by this commit fixes the problem for now but I cannot guarantee that this wont cause any side effects in a other context
* Adapted TransformationFacade to handle errors during transformation compilation
** errors generated during transformation compilation are returned through the generate member method
** throwing an exeception during TransformationFacade construction would require additional error handling in the calling code
* Added xalan::ProblemListener functionality to the ErrorHandler class
** XSLT problems passed to the ProblemListener are returned alongside to and treated as all other transformation errors

3 files changed, 90 insertions, 19 deletions

diff --git a/src/support/error_handler.cc b/src/support/error_handler.cc
index db54225..2ca721d 100644
--- a/src/support/error_handler.cc
+++ b/src/support/error_handler.cc
@@ -4,6 +4,7 @@
 
 #include <iostream>
 
+#include "support/xalan_string.h"
 #include "support/xerces_string_guard.h"
 
 namespace {
@@ -47,6 +48,52 @@ void ErrorHandler::fatalError(const xercesc::SAXParseException& exception) {
 
 void ErrorHandler::resetErrors() { }
 
+void ErrorHandler::problem(
+	xalan::ProblemListenerBase::eSource,
+	xalan::ProblemListenerBase::eClassification,
+	const xalan::XalanDOMString& message,
+	const xalan::Locator*,
+	const xalan::XalanNode*
+) {
+	this->constructErrorCache();
+
+	this->error_cache_->emplace_back(
+		"XSLT problem: " + toString(message)
+	);
+}
+
+void ErrorHandler::problem(
+	xalan::ProblemListenerBase::eSource,
+	xalan::ProblemListenerBase::eClassification,
+	const xalan::XalanNode*,
+	const xalan::ElemTemplateElement*,
+	const xalan::XalanDOMString& message,
+	const xalan::XalanDOMChar*,
+	xalan::XalanFileLoc,
+	xalan::XalanFileLoc
+) {
+	this->constructErrorCache();
+
+	this->error_cache_->emplace_back(
+		"XSLT problem: " + toString(message)
+	);
+}
+
+void ErrorHandler::problem(
+	xalan::ProblemListenerBase::eSource,
+	xalan::ProblemListenerBase::eClassification,
+	const xalan::XalanDOMString& message,
+	const xalan::XalanNode*
+) {
+	this->constructErrorCache();
+
+	this->error_cache_->emplace_back(
+		"XSLT problem: " + toString(message)
+	);
+}
+
+void ErrorHandler::setPrintWriter(xalan::PrintWriter*) { }
+
 auto ErrorHandler::getCachedErrors() -> error_cache_ptr {
 	return error_cache_ptr(this->error_cache_.release());
 }
diff --git a/src/support/error_handler.h b/src/support/error_handler.h
index 77a46d8..02d741e 100644
--- a/src/support/error_handler.h
+++ b/src/support/error_handler.h
@@ -2,14 +2,18 @@
 #define INPUTXSLT_SRC_SUPPORT_ERROR_HANDLER_H_
 
 #include <xercesc/sax/ErrorHandler.hpp>
+#include <xalanc/XSLT/ProblemListener.hpp>
 
 #include <memory>
 #include <vector>
 #include <string>
 
+#include "common.h"
+
 namespace InputXSLT {
 
-class ErrorHandler : public xercesc::ErrorHandler {
+class ErrorHandler : public xercesc::ErrorHandler,
+                     public xalan::ProblemListener {
 	public:
 		typedef std::vector<std::string> error_cache;
 		typedef std::unique_ptr<error_cache> error_cache_ptr;
@@ -21,6 +25,34 @@ class ErrorHandler : public xercesc::ErrorHandler {
 		virtual void fatalError(const xercesc::SAXParseException&);
 		virtual void resetErrors();
 
+		virtual void problem(
+			xalan::ProblemListenerBase::eSource,
+			xalan::ProblemListenerBase::eClassification,
+			const xalan::XalanDOMString&,
+			const xalan::Locator*,
+			const xalan::XalanNode*
+		);
+
+		virtual void problem(
+			xalan::ProblemListenerBase::eSource,
+			xalan::ProblemListenerBase::eClassification,
+			const xalan::XalanNode*,
+			const xalan::ElemTemplateElement*,
+			const xalan::XalanDOMString&,
+			const xalan::XalanDOMChar*,
+			xalan::XalanFileLoc,
+			xalan::XalanFileLoc
+		);
+
+		virtual void problem(
+			xalan::ProblemListenerBase::eSource,
+			xalan::ProblemListenerBase::eClassification,
+			const xalan::XalanDOMString&,
+			const xalan::XalanNode*
+		);
+
+		virtual void setPrintWriter(xalan::PrintWriter*);
+
 		error_cache_ptr getCachedErrors();
 
 	private:
diff --git a/src/transformation_facade.cc b/src/transformation_facade.cc
index 0f174d8..8b9e1a2 100644
--- a/src/transformation_facade.cc
+++ b/src/transformation_facade.cc
@@ -18,6 +18,7 @@ TransformationFacade::TransformationFacade(
 	error_handler_() {
 	this->transformer_.setEntityResolver(resolver);
 	this->transformer_.setErrorHandler(&this->error_handler_);
+	this->transformer_.setProblemListener(&this->error_handler_);
 
 	this->transformer_.compileStylesheet(
 		xalan::XSLTInputSource(transformation.data()),
@@ -66,27 +67,18 @@ auto TransformationFacade::generate(
 	xalan::XSLTResultTarget&& outputTarget,
 	StylesheetParameterGuard&
 ) -> return_type {
-	std::stringstream      emptyStream("<dummy/>");
-	xalan::XSLTInputSource inputSource(emptyStream);
-
-	const int resultCode = this->transformer_.transform(
-		inputSource,
-		this->transformation_,
-		outputTarget
-	);
-
-	return_type errors(this->error_handler_.getCachedErrors());
-
-	if ( errors && resultCode != 0 ) {
-		errors->emplace_back(
-			"Transformation error with code " +
-			std::to_string(resultCode)        +
-			": "                              +
-			this->transformer_.getLastError()
+	if ( this->transformation_ != nullptr ) {
+		std::stringstream      emptyStream("<dummy/>");
+		xalan::XSLTInputSource inputSource(emptyStream);
+
+		this->transformer_.transform(
+			inputSource,
+			this->transformation_,
+			outputTarget
 		);
 	}
 
-	return errors;
+	return this->error_handler_.getCachedErrors();
 }
 
 }