docarray · JoanFM · Jun 27, 2023 · Jun 27, 2023 · Jun 27, 2023 · Jun 27, 2023
diff --git a/docarray/array/any_array.py b/docarray/array/any_array.py
@@ -21,6 +21,7 @@
 
 from docarray.base_doc import BaseDoc
 from docarray.display.document_array_summary import DocArraySummary
+from docarray.exceptions.exceptions import UnusableObjectError
 from docarray.typing.abstract_type import AbstractType
 from docarray.utils._internal._typing import change_cls_name
 
@@ -32,6 +33,13 @@
 T_doc = TypeVar('T_doc', bound=BaseDoc)
 IndexIterType = Union[slice, Iterable[int], Iterable[bool], None]
 
+UNUSABLE_ERROR_MSG = (
+    'This {cls} instance is in an unusable state. \n'
+    'The most common cause of this is converting a DocVec to a DocList. '
+    'After you call `doc_vec.to_doc_list()`, `doc_vec` cannot be used anymore. '
+    'Instead, you should do `doc_list = doc_vec.to_doc_list()` and only use `doc_list`.'
+)
+
 
 class AnyDocArray(Sequence[T_doc], Generic[T_doc], AbstractType):
     doc_type: Type[BaseDoc]
@@ -64,9 +72,17 @@ class _DocArrayTyped(cls):  # type: ignore
 
                 def _property_generator(val: str):
                     def _getter(self):
+                        if getattr(self, '_is_unusable', False):
+                            raise UnusableObjectError(
+                                UNUSABLE_ERROR_MSG.format(cls=cls.__name__)
+                            )
                         return self._get_data_column(val)
 
                     def _setter(self, value):
+                        if getattr(self, '_is_unusable', False):
+                            raise UnusableObjectError(
+                                UNUSABLE_ERROR_MSG.format(cls=cls.__name__)
+                            )
                         self._set_data_column(val, value)
 
                     # need docstring for the property

diff --git a/docarray/array/doc_vec/doc_vec.py b/docarray/array/doc_vec/doc_vec.py
@@ -170,6 +170,7 @@ def __init__(
                 f'docs = DocVec[MyDoc](docs) instead of DocVec(docs)'
             )
         self.tensor_type = tensor_type
+        self._is_unusable = False
 
         tensor_columns: Dict[str, Optional[AbstractTensor]] = dict()
         doc_columns: Dict[str, Optional['DocVec']] = dict()
@@ -769,7 +770,14 @@ def to_doc_list(self: T) -> DocList[T_doc]:
 
         del self._storage
 
-        return DocList.__class_getitem__(self.doc_type).construct(docs)
+        doc_type = self.doc_type
+
+        # Setting _is_unusable will raise an Exception if someone interacts with this instance from hereon out.
+        # I don't like relying on this state, but we can't override the getattr/setattr directly:
+        # https://stackoverflow.com/questions/10376604/overriding-special-methods-on-an-instance
+        self._is_unusable = True
+
+        return DocList.__class_getitem__(doc_type).construct(docs)
 
     def traverse_flat(
         self,

diff --git a/docarray/exceptions/__init__.py b/docarray/exceptions/__init__.py
diff --git a/docarray/exceptions/exceptions.py b/docarray/exceptions/exceptions.py
@@ -0,0 +1,2 @@
+class UnusableObjectError(NotImplementedError):
+    ...
diff --git a/tests/units/array/stack/test_array_stacked.py b/tests/units/array/stack/test_array_stacked.py
@@ -8,6 +8,7 @@
 from docarray import BaseDoc, DocList
 from docarray.array import DocVec
 from docarray.documents import ImageDoc
+from docarray.exceptions.exceptions import UnusableObjectError
 from docarray.typing import AnyEmbedding, AnyTensor, NdArray, TorchTensor
 
 
@@ -657,3 +658,18 @@ class ImageDoc(BaseDoc):
     )
 
     assert da != da2
+
+
+def teste_unusable_state_raises_exception():
+    from docarray import DocVec
+    from docarray.documents import ImageDoc
+
+    docs = DocVec[ImageDoc]([ImageDoc(url='http://url.com/foo.png') for _ in range(10)])
+
+    docs.to_doc_list()
+
+    with pytest.raises(UnusableObjectError):
+        docs.url
+
+    with pytest.raises(UnusableObjectError):
+        docs.url = 'hi'
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		class UnusableObjectError(NotImplementedError):
		...