Improved TransformationFacade error handling

* ErrorHandler class created in 5859cb6 now caches all errors instead of pushing them to std::cerr
** cached errors are retrieved by TransformationFacade's "generate" member method
* test frontend pushes all errors to std::cerr
* FunctionTransform returns errors to the calling template as XML
** FunctionTransform test case demonstrates how one may test for successful transformation
* "generate" member method returns std::string vector wrapped in a std::unique_ptr
** this is used as a kind of optional pointer, as the std::unique_ptr instance only wraps a vector if errors where actually generated

3 files changed, 54 insertions, 26 deletions

diff --git a/src/support/error_handler.cc b/src/support/error_handler.cc
index 9a898a6..db54225 100644
--- a/src/support/error_handler.cc
+++ b/src/support/error_handler.cc
@@ -6,38 +6,55 @@
 
 #include "support/xerces_string_guard.h"
 
+namespace {
+
+inline std::string getMessage(const xercesc::SAXParseException& exception) {
+	return std::string(
+		*InputXSLT::XercesStringGuard<char>(exception.getMessage())
+	);
+}
+
+}
+
 namespace InputXSLT {
 
-ErrorHandler::ErrorHandler(const std::string& transformation):
-	transformation_path_(transformation) { }
+ErrorHandler::ErrorHandler():
+	error_cache_{} { }
+
+void ErrorHandler::warning(const xercesc::SAXParseException& exception) {
+	this->constructErrorCache();
 
-void ErrorHandler::warning(const xercesc::SAXParseException& e) {
-	std::cerr << "Warning in "
-	          << "'"
-	          << this->transformation_path_
-	          << "': "
-	          << *XercesStringGuard<char>(e.getMessage())
-	          << std::endl;
+	this->error_cache_->emplace_back(
+		"Warning: " + getMessage(exception)
+	);
 }
 
-void ErrorHandler::error(const xercesc::SAXParseException& e) {
-	std::cerr << "Error in "
-	          << "'"
-	          << this->transformation_path_
-	          << "': "
-	          << *XercesStringGuard<char>(e.getMessage())
-	          << std::endl;
+void ErrorHandler::error(const xercesc::SAXParseException& exception) {
+	this->constructErrorCache();
+
+	this->error_cache_->emplace_back(
+		"Error: " + getMessage(exception)
+	);
 }
 
-void ErrorHandler::fatalError(const xercesc::SAXParseException& e) {
-	std::cerr << "Fatal error in "
-	          << "'"
-	          << this->transformation_path_
-	          << "': "
-	          << *XercesStringGuard<char>(e.getMessage())
-	          << std::endl;
+void ErrorHandler::fatalError(const xercesc::SAXParseException& exception) {
+	this->constructErrorCache();
+
+	this->error_cache_->emplace_back(
+		"Fatal error: " + getMessage(exception)
+	);
 }
 
 void ErrorHandler::resetErrors() { }
 
+auto ErrorHandler::getCachedErrors() -> error_cache_ptr {
+	return error_cache_ptr(this->error_cache_.release());
+}
+
+void ErrorHandler::constructErrorCache() {
+	if ( !this->error_cache_ ) {
+		this->error_cache_.reset(new error_cache());
+	}
+}
+
 }
diff --git a/src/support/error_handler.h b/src/support/error_handler.h
index 7835292..77a46d8 100644
--- a/src/support/error_handler.h
+++ b/src/support/error_handler.h
@@ -3,21 +3,30 @@
 
 #include <xercesc/sax/ErrorHandler.hpp>
 
+#include <memory>
+#include <vector>
 #include <string>
 
 namespace InputXSLT {
 
 class ErrorHandler : public xercesc::ErrorHandler {
 	public:
-		ErrorHandler(const std::string&);
+		typedef std::vector<std::string> error_cache;
+		typedef std::unique_ptr<error_cache> error_cache_ptr;
+
+		ErrorHandler();
 
 		virtual void warning(const xercesc::SAXParseException&);
 		virtual void error(const xercesc::SAXParseException&);
 		virtual void fatalError(const xercesc::SAXParseException&);
 		virtual void resetErrors();
 
+		error_cache_ptr getCachedErrors();
+
 	private:
-		const std::string& transformation_path_;
+		error_cache_ptr error_cache_;
+
+		void constructErrorCache();
 
 };
 
diff --git a/src/support/include_entity_resolver.cc b/src/support/include_entity_resolver.cc
index 948a61b..e63a3c4 100644
--- a/src/support/include_entity_resolver.cc
+++ b/src/support/include_entity_resolver.cc
@@ -48,7 +48,9 @@ xercesc::InputSource* IncludeEntityResolver::resolveEntity(
 					*XercesStringGuard<XMLCh>((*resolvedPath).string())
 				);
 			} else {
-				return nullptr;
+				return new xercesc::LocalFileInputSource(
+					*XercesStringGuard<XMLCh>(*filePath)
+				);
 			}
 		} else {
 			return nullptr;