Attempt to add cause info

jpype/_jexception.py

@@ -32,6 +32,14 @@ class JException(_jpype._JException, internal=True):
     ``java.lang.Throwable``.
 
     """
+    def __new__(cls, *args):
+        self = _jpype._JException.__new__(cls, *args)
+        # Exceptions generated from Java require a different path.
+        if len(args) == 2 and type(args[1]) == tuple:
+            return self
+        # Connect the Java cause to the __cause__ field.
+        self.__cause__ = _jpype._java_lang_Throwable.getCause(self)
+        return self
 
     # Included for compatibility with JPype 0.6.3
     def message(self):

native/common/jp_class.cpp

@@ -382,8 +382,10 @@ JPPyObject JPClass::convertToPythonObject(JPJavaFrame& frame, jvalue value, bool
 						JPPyString::fromStringUTF8(frame.toString(value.l)).get()));
 			}
 		}
+		JPValue jv(cls, value);
+		JPPyObject cap = JPPyObject::claim(PyCapsule_New(&jv, JValueKey, NULL));
 		JPPyObject tuple1 = JPPyObject::call(PyTuple_Pack(2,
-				_JObjectKey, tuple0.get()));
+				cap.get(), tuple0.get()));
 		// Exceptions need new and init
 		obj = JPPyObject::call(PyObject_Call(wrapper.get(), tuple1.get(), NULL));
 	} else
@@ -393,10 +395,11 @@ JPPyObject JPClass::convertToPythonObject(JPJavaFrame& frame, jvalue value, bool
 		PyObject *obj2 = type->tp_alloc(type, 0);
 		JP_PY_CHECK();
 		obj = JPPyObject::claim(obj2);
+
+		// Fill in the Java slot
+		PyJPValue_assignJavaSlot(frame, obj.get(), JPValue(cls, value));
 	}
 
-	// Fill in the Java slot
-	PyJPValue_assignJavaSlot(frame, obj.get(), JPValue(cls, value));
 	return obj;
 	JP_TRACE_OUT;
 }

native/python/include/pyjp.h

@@ -151,9 +151,9 @@ extern PyObject *_JClassDoc;
 extern PyObject *_JMethodDoc;
 extern PyObject *_JMethodAnnotations;
 extern PyObject *_JMethodCode;
-extern PyObject *_JObjectKey;
 extern PyObject *_JVMNotRunning;
 extern PyObject* PyJPClassMagic;
+extern char* JValueKey;
 
 extern JPContext* JPContext_global;
 

native/python/pyjp_module.cpp

@@ -72,6 +72,7 @@ PyObject* _JMethodAnnotations = NULL;
 PyObject* _JMethodCode = NULL;
 PyObject* _JObjectKey = NULL;
 PyObject* _JVMNotRunning = NULL;
+char* JValueKey = "jvalue";
 
 void PyJPModule_loadResources(PyObject* module)
 {
@@ -121,8 +122,6 @@ void PyJPModule_loadResources(PyObject* module)
 		JP_PY_CHECK();
 		Py_INCREF(_JMethodCode);
 
-		_JObjectKey = PyCapsule_New(module, "constructor key", NULL);
-
 	}	catch (JPypeException&)  // GCOVR_EXCL_LINE
 	{
 		// GCOVR_EXCL_START

native/python/pyjp_object.cpp

@@ -22,6 +22,15 @@ extern "C"
 {
 #endif
 
+/** Construct a new PyJPObject.
+ * 
+ * This method is only called when Python is requesting a new object be constructed.
+ * If the object already exists, then the  JPClass::convertToPythonObject
+ * skips the new and init method and directly populates the fields.
+ *
+ * The only exception is Throwables which must be allocated using the 
+ * standard Python new/init paths.
+ */
 static PyObject *PyJPObject_new(PyTypeObject *type, PyObject *pyargs, PyObject *kwargs)
 {
 	JP_PY_TRY("PyJPObject_new");
@@ -247,14 +256,20 @@ static PyObject *PyJPException_new(PyTypeObject *type, PyObject *pyargs, PyObjec
 		return NULL;
 	}  // GCOVR_EXCL_STOP
 
-	// Special constructor path for Exceptions
-	JPPyObjectVector args(pyargs);
-	if (args.size() == 2 && args[0] == _JObjectKey)
-		return ((PyTypeObject*) PyExc_BaseException)->tp_new(type, args[1], kwargs);
-
 	// Create an instance (this may fail)
 	JPContext *context = PyJPModule_getContext();
 	JPJavaFrame frame = JPJavaFrame::outer(context);
+
+	// Special constructor path for Exceptions
+	JPPyObjectVector args(pyargs);
+	if (args.size() == 2 && PyCapsule_CheckExact(args[0]))
+	{
+		PyObject* self = ((PyTypeObject*) PyExc_BaseException)->tp_new(type, args[1], kwargs);
+		JPValue* jv = (JPValue*) PyCapsule_GetPointer(args[0], JValueKey);
+		PyJPValue_assignJavaSlot(frame, self, *jv);
+		return self;
+	}
+
 	JPValue jv = cls->newInstance(frame, args);
 
 	// Exception must be constructed with the BaseException_new
@@ -271,7 +286,7 @@ static int PyJPException_init(PyObject *self, PyObject *pyargs, PyObject *kwargs
 {
 	JP_PY_TRY("PyJPException_init");
 	JPPyObjectVector args(pyargs);
-	if (args.size() == 2 && args[0] == _JObjectKey)
+	if (args.size() == 2 && PyCapsule_CheckExact(args[0]))
 		return ((PyTypeObject*) PyExc_BaseException)->tp_init(self, args[1], kwargs);
 
 	// Exception must be constructed with the BaseException_new