#1311 better error handling during parse for schema and header

src/ifcopenshell-python/ifcopenshell/__init__.py

@@ -54,16 +54,36 @@ from . import guid
 from .file import file
 from .entity_instance import entity_instance
 
+READ_ERROR = ifcopenshell_wrapper.file_open_status.READ_ERROR
+NO_HEADER = ifcopenshell_wrapper.file_open_status.NO_HEADER
+UNSUPPORTED_SCHEMA = ifcopenshell_wrapper.file_open_status.UNSUPPORTED_SCHEMA
+
+
+class Error(Exception):
+    pass
+
+
+class SchemaError(Error):
+    pass
+
 
 def open(fn):
     f = ifcopenshell_wrapper.open(os.path.abspath(fn))
     if f.good():
         return file(f)
     else:
-        raise IOError("Unable to open file for reading")
+        exc, msg = {
+            READ_ERROR: (IOError, "Unable to open file for reading"),
+            NO_HEADER: (Error, "Unable to parse IFC SPF header"),
+            UNSUPPORTED_SCHEMA: (
+                SchemaError,
+                "Unsupported schema: %s" % ",".join(f.header.file_schema.schema_identifiers),
+            ),
+        }[f.good().value()]
+        raise exc(msg)
 
 
-def create_entity(type, schema='IFC4', *args, **kwargs):
+def create_entity(type, schema="IFC4", *args, **kwargs):
     e = entity_instance((schema, type))
     attrs = list(enumerate(args)) + [(e.wrapped_data.get_argument_index(name), arg) for name, arg in kwargs.items()]
     for idx, arg in attrs:

src/ifcparse/IfcFile.h

@@ -33,6 +33,36 @@
 
 namespace IfcParse {
 
+class IFC_PARSE_API file_open_status {
+public:
+	enum file_open_enum {
+		SUCCESS,
+		READ_ERROR,
+		NO_HEADER,
+		UNSUPPORTED_SCHEMA
+	};
+
+private:
+	file_open_enum error_;
+
+public:
+	file_open_status(file_open_enum error)
+		: error_(error)
+	{}
+
+	operator file_open_enum() const {
+		return error_;
+	}
+
+	file_open_enum value() const {
+		return error_;
+	}
+
+	operator bool() const {
+		return error_ == SUCCESS;
+	}
+};
+
 /// This class provides several static convenience functions and variables
 /// and provide access to the entities in an IFC file
 class IFC_PARSE_API IfcFile {
@@ -78,7 +108,8 @@ public:
 private:
 	typedef std::map<IfcUtil::IfcBaseClass*, IfcUtil::IfcBaseClass*> entity_entity_map_t;
 
-	bool parsing_complete_, good_;
+	bool parsing_complete_;
+	file_open_status good_ = file_open_status::SUCCESS;
 
 	const IfcParse::schema_definition* schema_;
 	const IfcParse::declaration* ifcroot_type_;
@@ -116,7 +147,7 @@ public:
 
 	virtual ~IfcFile();
 
-	bool good() const { return good_; }
+	file_open_status good() const { return good_; }
 	
 	/// Returns the first entity in the file, this probably is the entity
 	/// with the lowest id (EXPRESS ENTITY_INSTANCE_NAME)

src/ifcparse/IfcParse.cpp

@@ -1326,7 +1326,6 @@ IfcFile::IfcFile(IfcParse::IfcSpfStream* s) {
 
 IfcFile::IfcFile(const IfcParse::schema_definition* schema)
 	: parsing_complete_(true)
-	, good_(true)
 	, schema_(schema)
 	, ifcroot_type_(schema_->declaration_by_name("IfcRoot"))
 	, MaxId(0)
@@ -1341,8 +1340,6 @@ void IfcFile::initialize_(IfcParse::IfcSpfStream* s) {
 	// number parsing. See comment above on line 41.
 	init_locale();
 
-	good_ = false;
-
 	parsing_complete_ = false;
 	MaxId = 0;
 	tokens = 0;
@@ -1353,24 +1350,30 @@ void IfcFile::initialize_(IfcParse::IfcSpfStream* s) {
 	
 	stream = s;
 	if (!stream->valid) {
+		good_ = file_open_status::READ_ERROR;
 		return;
 	}
 
 	tokens = new IfcSpfLexer(stream, this);
-	_header.file(this);
-	_header.tryRead();
-
+	
 	std::vector<std::string> schemas;
-	try {
-		schemas = _header.file_schema().schema_identifiers();
-	} catch (...) {
-		// Purposely empty catch block
+
+	_header.file(this);
+	if (_header.tryRead()) {
+		try {
+			schemas = _header.file_schema().schema_identifiers();
+		} catch (...) {
+			// Purposely empty catch block
+		}
+	} else {
+		good_ = file_open_status::NO_HEADER;
 	}
 
 	if (schemas.size() == 1) {
 		try {
 			schema_ = IfcParse::schema_by_name(schemas.front());
 		} catch (const IfcParse::IfcException& e) {
+			good_ = file_open_status::UNSUPPORTED_SCHEMA;
 			Logger::Error(e);
 		}
 	}
@@ -1381,8 +1384,6 @@ void IfcFile::initialize_(IfcParse::IfcSpfStream* s) {
 		return;
 	}
 
-	good_ = true;
-
 	ifcroot_type_ = schema_->declaration_by_name("IfcRoot");
 
 	boost::circular_buffer<Token> token_stream(3, Token());