feat: Add error output to suggest possible causes when scenario parsing fails

model/main.cpp

@@ -304,35 +304,48 @@ int main(int argc, char* argv[])
     } catch (const OM::util::cmd_exception& e) {
         if( e.getCode() == 0 ){
             // this is not an error, but exiting due to command line
-            cerr << e.what() << "; exiting..." << endl;
+            std::cerr << e.what() << "; exiting..." << endl;
         }else{
-            cerr << "Command-line error: "<<e.what();
+            std::cerr << "Command-line error: "<<e.what();
             exitStatus = e.getCode();
         }
     } catch (const ::xsd::cxx::tree::exception<char>& e) {
-        cerr << "XSD error: " << e.what() << '\n' << e << endl;
+        if (errno == 2) // Errno value 2 corresponds to "No such file or directory" i.e. this is not a mismatch between scenario contents and schema rules.
+        {
+            // We don't print the content of the xsdcxx exception since the error messages are not relevant to the user in this case.
+            std::cerr << "Parsing scenario file failed.\n\tLikely the XSD schema file is not present at an expected location/with expected filename." << std::endl;
+        }
+        else
+        {
+            // e.what() returns a concise error message e.g. "instance document parsing failed".
+            // Whereas inserting e into a stream inserts the (possibly long and repetitive) list of error messages arising from the parsing attempt.
+            std::cerr << "XSD error: " << e.what() << '\n' << e << endl;
+
+            // We print this *after* the above since users are more likely to take note of the tail of stderr/stdout output than the head.
+            std::cerr << "Parsing scenario file failed.\n\tLikely the XSD schema is named/located correctly but the scenario does not conform to the schema." << std::endl;
+        }
         exitStatus = OM::util::Error::XSD;
     } catch (const OM::util::checkpoint_error& e) {
-        cerr << "Checkpoint error: " << e.what() << endl;
-        cerr << e << flush;
+        std::cerr << "Checkpoint error: " << e.what() << endl;
+        std::cerr << e << flush;
         exitStatus = e.getCode();
     } catch (const OM::util::traced_exception& e) {
-        cerr << "Code error: " << e.what() << endl;
-        cerr << e << flush;
-        cerr << "This is likely an error in the C++ code. Please report!" << endl;
+        std::cerr << "Code error: " << e.what() << endl;
+        std::cerr << e << flush;
+        std::cerr << "This is likely an error in the C++ code. Please report!" << endl;
         exitStatus = e.getCode();
     } catch (const OM::util::xml_scenario_error& e) {
-        cerr << "Error: " << e.what() << endl;
-        cerr << "In: " << scenarioFile << endl;
+        std::cerr << "Error: " << e.what() << endl;
+        std::cerr << "In: " << scenarioFile << endl;
         exitStatus = e.getCode();
     } catch (const OM::util::base_exception& e) {
-        cerr << "Error: " << e.message() << endl;
+        std::cerr << "Error: " << e.message() << endl;
         exitStatus = e.getCode();
     } catch (const exception& e) {
-        cerr << "Error: " << e.what() << endl;
+        std::cerr << "Error: " << e.what() << endl;
         exitStatus = EXIT_FAILURE;
     } catch (...) {
-        cerr << "Unknown error" << endl;
+        std::cerr << "Unknown error" << endl;
         exitStatus = EXIT_FAILURE;
     }
 

model/util/DocumentLoader.cpp

@@ -28,34 +28,34 @@ namespace OM
 { 
     namespace util
     {
-        unique_ptr<scnXml::Scenario> loadScenario(std::string lXmlFile)
+        std::unique_ptr<scnXml::Scenario> loadScenario(std::string lXmlFile)
         {
             // Opening by filename causes a schema lookup in the scenario file's dir,
             // which does always work. Opening with a stream uses the working directory.
 
             // Note that the schema location can be set manually by passing properties,
             // but we won't necessarily have the right schema version associated with
             // the XML file in that case.
-            ifstream fileStream(lXmlFile.c_str(), ios::binary);
+            std::ifstream fileStream(lXmlFile.c_str(), ios::binary);
             if (!fileStream.good())
             {
-                string msg = "Error: unable to open " + lXmlFile;
+                std::string msg = "Error: unable to open " + lXmlFile;
                 throw util::xml_scenario_error(msg);
             }
-            unique_ptr<scnXml::Scenario> scenario = scnXml::parseScenario (fileStream);
+            std::unique_ptr<scnXml::Scenario> scenario = scnXml::parseScenario (fileStream);
             fileStream.close ();
 
-            int scenarioVersion = scenario->getSchemaVersion();
+            const int scenarioVersion = scenario->getSchemaVersion();
 
             if (scenarioVersion < SCHEMA_VERSION) {
                 // Don't bother aborting. Mostly if something really is incompatible
                 // loading will not succeed anyway.
-                cerr<<"Warning: "<<lXmlFile<<" uses an old schema version (latest is "<<SCHEMA_VERSION<<")."<<endl;
+                std::cerr<<"Warning: "<<lXmlFile<<" uses an old schema version (latest is "<<SCHEMA_VERSION<<")."<<endl;
             }
             else if (scenarioVersion > SCHEMA_VERSION)
                 throw util::xml_scenario_error ("Error: new schema version unsupported");
 
             return scenario;
         }
     }
-}
+}

model/util/DocumentLoader.h

@@ -37,7 +37,7 @@ namespace OM
     {
         static const int SCHEMA_VERSION = 48;
 
-        unique_ptr<scnXml::Scenario> loadScenario(std::string lXmlFile);
+        std::unique_ptr<scnXml::Scenario> loadScenario(std::string lXmlFile);
     }
 }