Exceptions (#14)

* can get single line as exception

* returns exceptions now

* remove stream code

src/main.cpp

@@ -1,4 +1,6 @@
+#include <sstream>
 #include <Python.h>
+#include <frameobject.h>
 // #include <datetime.h>
 #ifdef COMPILER
 #undef COMPILER
@@ -196,9 +198,41 @@ class CallWorker : public Nan::AsyncWorker {
 
         Py_DECREF(pValue);
       } else {
+        std::string error;
+        PyObject * errOccurred = PyErr_Occurred();
+        if (errOccurred != NULL) {
+          PyObject *pType, *pValue, *pTraceback, *pTypeString;
+          PyErr_Fetch(&pType, &pValue, &pTraceback);
+          const char * value = PyUnicode_AsUTF8(pValue);
+          pTypeString = PyObject_Str(pType);
+          const char * type = PyUnicode_AsUTF8(pTypeString);
+
+          PyTracebackObject * tb = (PyTracebackObject *)pTraceback;
+          std::ostringstream stream;
+          _frame * frame = tb->tb_frame;
+
+          while (frame != NULL) {
+            int line = PyCode_Addr2Line(frame->f_code, frame->f_lasti);
+            const char * filename = PyUnicode_AsUTF8(frame->f_code->co_filename);
+            const char * funcname = PyUnicode_AsUTF8(frame->f_code->co_name);
+            stream << "File \"" << filename << "\", line " << line << ", in " << funcname << "\n";
+            stream << type << ": " << value;
+            frame = frame->f_back;
+          }
+
+          error.append(stream.str());
+
+          Py_DecRef(errOccurred);
+          Py_DecRef(pTypeString);
+          PyErr_Restore(pType, pValue, pTraceback);
+        } else {
+          error.append("Function call failed");
+        }
+
         Py_DecRef(pFunc);
         PyErr_Print();
-        argv[0] = Nan::Error("Function call failed");
+
+        argv[0] = Nan::Error(error.c_str());
       }
 
       callback->Call(2, argv);

test.js

@@ -25,6 +25,17 @@ describe('nodePython', () => {
   })
 
   describe('#call', () => {
+    it('should return the stack trace', done => {
+      call('causes_runtime_error')
+        .then(result => console.log('should not see this : ', result))
+        .catch(err => {
+          expect(err.message.includes('tools.py')).to.equal(true)
+          expect(err.message.includes('in causes_runtime_error')).to.equal(true)
+          expect(err.message.includes('name \'secon\' is not defined')).to.equal(true)
+          done()
+        })
+    })
+
     it('should return the time series data', done => {
       call('time_series_data')
         .then(result => {

test_files/tools.py

@@ -38,3 +38,8 @@ def return_dict():
 def return_tuple():
   x = (1, 2, 3)
   return x
+
+def causes_runtime_error():
+  first = 1
+  second = 2
+  return first + secon