Implemented WarningCapacitor as a counterpart to ErrorCapacitor

* in difference to ErrorCapacitor this class doesn't throw an exception on "discharge" but returns the gathered warnings
* adapted FunctionTransform and frontend error handling to include warnings
* added static "try_create" method to TransformationFacade
** wraps construction error handling
** custom logic may be embedded using the std::function argument
*** this was implemented to prevent unneccessary code duplication for handling both construction and generation errors
* adapted FunctionTransform to return warning as "warning" nodes in the result tree
** added functional lambda expression factory method "handleErrors"
*** returns a error handling lambda expression for a given ResultNodeFacade
* implemented WarningGuard class in frontend executable
** guarantees warnings to be printed to std::cerr independent of any exceptions

1 files changed, 23 insertions, 3 deletions

diff --git a/src/transformation_facade.cc b/src/transformation_facade.cc
index 6d7b7a3..3c94bdd 100644
--- a/src/transformation_facade.cc
+++ b/src/transformation_facade.cc
@@ -7,17 +7,33 @@
 
 #include <sstream>
 
-#include "support/error/error_capacitor.h"
-
 namespace InputXSLT {
 
+auto TransformationFacade::try_create(
+	const std::string& transformation,
+	IncludeEntityResolver* resolver,
+	const std::function<void(const ErrorCapacitor::error_cache&)>& handleErrors
+) -> ptr{
+	try {
+		return ptr(
+			new InputXSLT::TransformationFacade(transformation, resolver)
+		);
+	}
+	catch (const ErrorCapacitor::exception& exception) {
+		handleErrors(*exception);
+
+		return ptr();
+	}
+}
+
 TransformationFacade::TransformationFacade(
 	const std::string& transformation,
 	IncludeEntityResolver* resolver
 ):
 	transformation_{},
 	transformer_(),
-	error_multiplexer_(&transformer_) {
+	error_multiplexer_(&transformer_),
+	warning_capacitor_(&error_multiplexer_) {
 	this->transformer_.setEntityResolver(resolver);
 
 	ErrorCapacitor errorCapacitor(&this->error_multiplexer_);
@@ -36,6 +52,10 @@ TransformationFacade::~TransformationFacade() {
 	);
 }
 
+WarningCapacitor::warning_cache_ptr TransformationFacade::getCachedWarnings() {
+	return this->warning_capacitor_.discharge();
+}
+
 void TransformationFacade::generate(
 	const std::string& targetPath,
 	StylesheetParameterGuard& parameters