1 files changed, 33 insertions, 14 deletions

diff --git a/python/google/protobuf/pyext/extension_dict.cc b/python/google/protobuf/pyext/extension_dict.cc
index b361b342..555bd293 100644
--- a/python/google/protobuf/pyext/extension_dict.cc
+++ b/python/google/protobuf/pyext/extension_dict.cc
@@ -94,13 +94,13 @@ PyObject* subscript(ExtensionDict* self, PyObject* key) {
   if (descriptor == NULL) {
     return NULL;
   }
-  if (!CheckFieldBelongsToMessage(descriptor, self->parent->message)) {
+  if (!CheckFieldBelongsToMessage(descriptor, self->message)) {
     return NULL;
   }
 
   if (descriptor->label() != FieldDescriptor::LABEL_REPEATED &&
       descriptor->cpp_type() != FieldDescriptor::CPPTYPE_MESSAGE) {
-    return cmessage::InternalGetScalar(self->parent->message, descriptor);
+    return cmessage::InternalGetScalar(self->message, descriptor);
   }
 
   PyObject* value = PyDict_GetItem(self->values, key);
@@ -109,6 +109,14 @@ PyObject* subscript(ExtensionDict* self, PyObject* key) {
     return value;
   }
 
+  if (self->parent == NULL) {
+    // We are in "detached" state. Don't allow further modifications.
+    // TODO(amauryfa): Support adding non-scalars to a detached extension dict.
+    // This probably requires to store the type of the main message.
+    PyErr_SetObject(PyExc_KeyError, key);
+    return NULL;
+  }
+
   if (descriptor->label() != FieldDescriptor::LABEL_REPEATED &&
       descriptor->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE) {
     PyObject* sub_message = cmessage::InternalGetSubMessage(
@@ -154,7 +162,7 @@ int ass_subscript(ExtensionDict* self, PyObject* key, PyObject* value) {
   if (descriptor == NULL) {
     return -1;
   }
-  if (!CheckFieldBelongsToMessage(descriptor, self->parent->message)) {
+  if (!CheckFieldBelongsToMessage(descriptor, self->message)) {
     return -1;
   }
 
@@ -164,9 +172,11 @@ int ass_subscript(ExtensionDict* self, PyObject* key, PyObject* value) {
                     "type");
     return -1;
   }
-  cmessage::AssureWritable(self->parent);
-  if (cmessage::InternalSetScalar(self->parent, descriptor, value) < 0) {
-    return -1;
+  if (self->parent) {
+    cmessage::AssureWritable(self->parent);
+    if (cmessage::InternalSetScalar(self->parent, descriptor, value) < 0) {
+      return -1;
+    }
   }
   // TODO(tibell): We shouldn't write scalars to the cache.
   PyDict_SetItem(self->values, key, value);
@@ -180,15 +190,17 @@ PyObject* ClearExtension(ExtensionDict* self, PyObject* extension) {
     return NULL;
   }
   PyObject* value = PyDict_GetItem(self->values, extension);
-  if (value != NULL) {
-    if (ReleaseExtension(self, value, descriptor) < 0) {
+  if (self->parent) {
+    if (value != NULL) {
+      if (ReleaseExtension(self, value, descriptor) < 0) {
+        return NULL;
+      }
+    }
+    if (ScopedPyObjectPtr(cmessage::ClearFieldByDescriptor(
+            self->parent, descriptor)) == NULL) {
       return NULL;
     }
   }
-  if (ScopedPyObjectPtr(cmessage::ClearFieldByDescriptor(
-          self->parent, descriptor)) == NULL) {
-    return NULL;
-  }
   if (PyDict_DelItem(self->values, extension) < 0) {
     PyErr_Clear();
   }
@@ -201,8 +213,15 @@ PyObject* HasExtension(ExtensionDict* self, PyObject* extension) {
   if (descriptor == NULL) {
     return NULL;
   }
-  PyObject* result = cmessage::HasFieldByDescriptor(self->parent, descriptor);
-  return result;
+  if (self->parent) {
+    return cmessage::HasFieldByDescriptor(self->parent, descriptor);
+  } else {
+    int exists = PyDict_Contains(self->values, extension);
+    if (exists < 0) {
+      return NULL;
+    }
+    return PyBool_FromLong(exists);
+  }
 }
 
 PyObject* _FindExtensionByName(ExtensionDict* self, PyObject* name) {