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

6 files changed, 96 insertions, 55 deletions

diff --git a/src/function/transform.cc b/src/function/transform.cc
index fd28b34..7e8a844 100644
--- a/src/function/transform.cc
+++ b/src/function/transform.cc
@@ -38,17 +38,22 @@ xercesc::DOMDocument* FunctionTransform::constructDocument(
 		domDocument->getDocumentElement()
 	);
 
+	ResultNodeFacade result(domDocument, rootNode, "result");
+	result.setAttribute("name", targetPath);
+
 	InputXSLT::TransformationFacade transformation(
 		transformationPath,
 		this->include_resolver_
 	);
 
-	if ( transformation.generate(targetPath, parameterObject) == 0 ) {
-		ResultNodeFacade result(domDocument, rootNode, "result");
+	InputXSLT::TransformationFacade::return_type errors(
+		transformation.generate(targetPath, parameterObject)
+	);
 
-		result.setAttribute("name", targetPath);
-	} else {
-		ResultNodeFacade result(domDocument, rootNode, "error");
+	if ( errors ) {
+		for ( auto&& error : *errors ) {
+			result.setValueNode("error", error);
+		}
 	}
 
 	return domDocument;
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;
diff --git a/src/transformation_facade.cc b/src/transformation_facade.cc
index fc7e1de..0f174d8 100644
--- a/src/transformation_facade.cc
+++ b/src/transformation_facade.cc
@@ -6,7 +6,6 @@
 #include "boost/filesystem.hpp"
 
 #include <sstream>
-#include <iostream>
 
 namespace InputXSLT {
 
@@ -16,7 +15,7 @@ TransformationFacade::TransformationFacade(
 ):
 	transformation_{},
 	transformer_(),
-	error_handler_(transformation) {
+	error_handler_() {
 	this->transformer_.setEntityResolver(resolver);
 	this->transformer_.setErrorHandler(&this->error_handler_);
 
@@ -32,10 +31,10 @@ TransformationFacade::~TransformationFacade() {
 	);
 }
 
-int TransformationFacade::generate(
+auto TransformationFacade::generate(
 	const std::string& targetPath,
 	StylesheetParameterGuard& parameters
-) {
+) -> return_type {
 	const boost::filesystem::path targetPathHelper(
 		boost::filesystem::absolute(targetPath)
 	);
@@ -53,22 +52,22 @@ int TransformationFacade::generate(
 	);
 }
 
-int TransformationFacade::generate(
+auto TransformationFacade::generate(
 	std::basic_ostream<char>& targetStream,
 	StylesheetParameterGuard& parameters
-) {
+) -> return_type {
 	return this->generate(
 		xalan::XSLTResultTarget(targetStream),
 		parameters
 	);
 }
 
-int TransformationFacade::generate(
+auto TransformationFacade::generate(
 	xalan::XSLTResultTarget&& outputTarget,
 	StylesheetParameterGuard&
-) {
-	std::stringstream       emptyStream("<dummy/>");
-	xalan::XSLTInputSource  inputSource(emptyStream);
+) -> return_type {
+	std::stringstream      emptyStream("<dummy/>");
+	xalan::XSLTInputSource inputSource(emptyStream);
 
 	const int resultCode = this->transformer_.transform(
 		inputSource,
@@ -76,11 +75,18 @@ int TransformationFacade::generate(
 		outputTarget
 	);
 
-	if ( resultCode != 0 ) {
-		std::cerr << this->transformer_.getLastError() << std::endl;
+	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()
+		);
 	}
 
-	return resultCode;
+	return errors;
 }
 
 }
diff --git a/src/transformation_facade.h b/src/transformation_facade.h
index ab76cac..28d1895 100644
--- a/src/transformation_facade.h
+++ b/src/transformation_facade.h
@@ -14,17 +14,19 @@ namespace InputXSLT {
 
 class TransformationFacade {
 	public:
+		typedef ErrorHandler::error_cache_ptr return_type;
+
 		TransformationFacade(const std::string&, IncludeEntityResolver*);
 		~TransformationFacade();
 
 		template <typename Target>
-		int generate(Target&);
+		return_type generate(Target&);
 
 		template <typename Target>
-		int generate(Target&, const StylesheetParameterGuard::map&);
+		return_type generate(Target&, const StylesheetParameterGuard::map&);
 
 		template <typename Target>
-		int generate(Target&, const xalan::XObjectPtr&);
+		return_type generate(Target&, const xalan::XObjectPtr&);
 
 	private:
 		const xalan::XalanCompiledStylesheet* transformation_;
@@ -32,34 +34,34 @@ class TransformationFacade {
 		xalan::XalanTransformer transformer_;
 		ErrorHandler error_handler_;
 
-		int generate(const std::string&, StylesheetParameterGuard&);
-		int generate(std::basic_ostream<char>&, StylesheetParameterGuard&);
-		int generate(xalan::XSLTResultTarget&&, StylesheetParameterGuard&);
+		return_type generate(const std::string&, StylesheetParameterGuard&);
+		return_type generate(std::basic_ostream<char>&, StylesheetParameterGuard&);
+		return_type generate(xalan::XSLTResultTarget&&, StylesheetParameterGuard&);
 
 };
 
 template <typename Target>
-int TransformationFacade::generate(Target& target) {
+auto TransformationFacade::generate(Target& target) -> return_type {
 	StylesheetParameterGuard guard(this->transformer_);
 
 	return this->generate(target, guard);
 }
 
 template <typename Target>
-int TransformationFacade::generate(
+auto TransformationFacade::generate(
 	Target& target,
 	const StylesheetParameterGuard::map& parameters
-) {
+) -> return_type {
 	StylesheetParameterGuard guard(this->transformer_, parameters);
 
 	return this->generate(target, guard);
 }
 
 template <typename Target>
-int TransformationFacade::generate(
+auto TransformationFacade::generate(
 	Target& target,
 	const xalan::XObjectPtr& parameter
-) {
+) -> return_type {
 	StylesheetParameterGuard guard(this->transformer_);
 	guard.set("parameters", parameter);