fix: correct Table.update transform type hints

tests/test_tinydb.py

@@ -278,6 +278,26 @@ def transform(el):
     assert db.count(where('int') == 1) == 2
 
 
+def test_update_custom_transform_callable(db: TinyDB):
+    from collections.abc import MutableMapping
+
+    from tinydb.operations import delete as delete_field
+
+    doc_id = db.insert({'name': 'John', 'temp': True})
+
+    def remove_temp(doc: MutableMapping) -> None:
+        del doc['temp']
+
+    db.update(remove_temp, where('name') == 'John')
+
+    assert db.get(doc_id=doc_id) == {'name': 'John'}
+
+    db.update({'temp': True}, where('name') == 'John')
+    db.update(delete_field('temp'), where('name') == 'John')
+
+    assert db.get(doc_id=doc_id) == {'name': 'John'}
+
+
 def test_update_ids(db: TinyDB):
     db.update({'int': 2}, doc_ids=[1, 2])
 

tinydb/table.py

@@ -3,7 +3,7 @@
 data in TinyDB.
 """
 
-from collections.abc import Callable, Iterable, Iterator, Mapping
+from collections.abc import Callable, Iterable, Iterator, Mapping, MutableMapping
 from typing import (
     NoReturn,
     Optional,
@@ -403,7 +403,7 @@ def contains(
 
     def update(
         self,
-        fields: Union[Mapping, Callable[[Mapping], None]],
+        fields: Union[Mapping, Callable[[MutableMapping], None]],
         cond: Optional[QueryLike] = None,
         doc_ids: Optional[Iterable[int]] = None,
     ) -> list[int]:
@@ -415,7 +415,7 @@ def update(
         the IDs that were actually updated.
 
         :param fields: the fields that the matching documents will have
-                       or a method that will update the documents
+                       or a callable that mutates matching documents in place
         :param cond: which documents to update
         :param doc_ids: a list of document IDs
         :returns: a list containing the updated document's ID
@@ -508,7 +508,7 @@ def updater(table: dict):
     def update_multiple(
         self,
         updates: Iterable[
-            tuple[Union[Mapping, Callable[[Mapping], None]], QueryLike]
+            tuple[Union[Mapping, Callable[[MutableMapping], None]], QueryLike]
         ],
     ) -> list[int]:
         """