Add new exception CursorCountError for when cursor count is not set but used

Author: joowani

arango/cursor.py

@@ -5,10 +5,11 @@
 from collections import deque
 
 from arango.exceptions import (
-    CursorNextError,
     CursorCloseError,
+    CursorEmptyError,
+    CursorNextError,
     CursorStateError,
-    CursorEmptyError
+    CursorCountError
 )
 from arango.request import Request
 
@@ -63,6 +64,8 @@ def __enter__(self):
         return self
 
     def __len__(self):
+        if self._count is None:
+            raise CursorCountError('cursor count not enabled')
         return self._count
 
     def __exit__(self, *_):

arango/exceptions.py

@@ -266,6 +266,10 @@ class CursorStateError(ArangoClientError):
     """The cursor object was in a bad state."""
 
 
+class CursorCountError(ArangoClientError, TypeError):
+    """The cursor count was not enabled."""
+
+
 class CursorEmptyError(ArangoClientError):
     """The current batch in cursor was empty."""
 

tests/test_cursor.py

@@ -4,6 +4,7 @@
 
 from arango.exceptions import (
     CursorCloseError,
+    CursorCountError,
     CursorEmptyError,
     CursorNextError,
     CursorStateError,
@@ -270,6 +271,22 @@ def test_cursor_no_count(db, col):
         optimizer_rules=['+all'],
         profile=True
     )
+    with pytest.raises(CursorCountError) as err:
+        _ = len(cursor)
+    assert err.value.message == 'cursor count not enabled'
+
+    with pytest.raises(CursorCountError) as err:
+        _ = bool(cursor)
+    assert err.value.message == 'cursor count not enabled'
+
     while cursor.has_more():
         assert cursor.count() is None
+
+        with pytest.raises(CursorCountError) as err:
+            _ = len(cursor)
+        assert err.value.message == 'cursor count not enabled'
+
+        with pytest.raises(CursorCountError) as err:
+            _ = bool(cursor)
+        assert err.value.message == 'cursor count not enabled'
         assert cursor.fetch()