Fix bug #1008 in the json_schema export of document with BackLink

beanie/odm/fields.py

@@ -487,7 +487,17 @@ def validate(v: Union[DBRef, T], field):
         def __get_pydantic_core_schema__(
             cls, source_type: Any, handler: GetCoreSchemaHandler
         ) -> CoreSchema:  # type: ignore
-            return plain_validator(cls.build_validation(handler, source_type))
+            # build_validation can return any object
+            # so json_schema should be a general dict
+            return core_schema.json_or_python_schema(
+                python_schema=plain_validator(
+                    cls.build_validation(handler, source_type),
+                ),
+                json_schema=core_schema.dict_schema(
+                    keys_schema=core_schema.str_schema(),
+                    values_schema=core_schema.any_schema(),
+                ),
+            )
 
     else:
 

tests/odm/test_relations.py

@@ -839,6 +839,18 @@ async def test_write_list(self, list_link_and_list_backlink_doc_pair):
         for lnk in new_back_link_doc.back_link:
             assert lnk.s == "new value"
 
+    def test_json_schema_export(self):
+        if IS_PYDANTIC_V2:
+            json_schema = DocumentWithListBackLink.model_json_schema()
+        else:
+            return  # schema does not work in pydantic v1 due to pydantic bug #3390
+            json_schema = DocumentWithListBackLink.schema()
+
+        assert (
+            json_schema["properties"]["back_link"]["items"]
+            and json_schema["properties"]["back_link"]["type"] == "array"
+        )
+
 
 class HouseForReversedOrderInit(Document):
     name: str