explicit error in case of misuse of dg.plug, fix #36

src/dynamic_graph/dynamic-graph-py.cc

@@ -17,7 +17,13 @@ namespace python {
 /**
    \brief plug a signal into another one.
 */
-PyObject* plug(PyObject* /*self*/, PyObject* args) {
+PyObject* plug(
+#if PY_MAJOR_VERSION >= 3
+    PyObject* m, PyObject* args
+#else
+    PyObject*, PyObject* args
+#endif
+    ) {
   PyObject* objOut = NULL;
   PyObject* objIn = NULL;
   void* pObjOut;
@@ -40,10 +46,22 @@ PyObject* plug(PyObject* /*self*/, PyObject* args) {
 
   pObjIn = PyCapsule_GetPointer(objIn, "dynamic_graph.Signal");
   SignalBase<int>* signalIn = (SignalBase<int>*)pObjIn;
-  if (signalIn == NULL) return NULL;
+  if (signalIn == NULL) {
+      struct module_state* st = GETSTATE(m);
+      std::ostringstream oss;
+      oss << "dgpy.plug in argument must be a dynamic_graph.Signal, not a " << PyCapsule_GetName(objIn);
+      PyErr_SetString(st->dgpyError, oss.str().c_str());
+      return NULL;
+  }
   pObjOut = PyCapsule_GetPointer(objOut, "dynamic_graph.Signal");
   SignalBase<int>* signalOut = (SignalBase<int>*)pObjOut;
-  if (signalOut == NULL) return NULL;
+  if (signalOut == NULL) {
+      struct module_state* st = GETSTATE(m);
+      std::ostringstream oss;
+      oss << "dgpy.plug out argument must be a dynamic_graph.Signal, not a " << PyCapsule_GetName(objOut);
+      PyErr_SetString(st->dgpyError, oss.str().c_str());
+      return NULL;
+  }
   std::ostringstream os;
 
   try {
@@ -123,6 +141,14 @@ void initwrap(void)
     INITERROR;
   }
 
+  Py_XINCREF(st->dgpyError);
+  if (PyModule_AddObject(module, "dgpyError", st->dgpyError) < 0) {
+    Py_XDECREF(st->dgpyError);
+    Py_CLEAR(st->dgpyError);
+    Py_DECREF(module);
+    return NULL;
+  }
+
 #if PY_MAJOR_VERSION >= 3
   return module;
 #endif

unitTesting/test_bindings.py

 import unittest
 
 import dynamic_graph as dg
+
 from custom_entity import CustomEntity
 
 
@@ -15,10 +16,18 @@ class BindingsTests(unittest.TestCase):
         second = CustomEntity('second_entity')
         # Check that we can connect first.out to second.in
         dg.plug(first.signal('out_double'), second.signal('in_double'))
+
         # Check that we can't connect first.out to second
-        with self.assertRaises(ValueError) as cm:
+        with self.assertRaises(dg.dgpyError) as cm_in:
             dg.plug(first.signal('out_double'), second)
-        self.assertEqual(str(cm.exception), "PyCapsule_GetPointer called with incorrect name")
+        self.assertEqual(str(cm_in.exception),
+                         "dgpy.plug in argument must be a dynamic_graph.Signal, not a dynamic_graph.Entity")
+
+        # Check that we can't connect first to second.in
+        with self.assertRaises(dg.dgpyError) as cm_out:
+            dg.plug(first, second.signal('in_double'))
+        self.assertEqual(str(cm_out.exception),
+                         "dgpy.plug out argument must be a dynamic_graph.Signal, not a dynamic_graph.Entity")
 
 
 if __name__ == '__main__':