checkpoint-postgres: handle null chars in metadata (#1885)

libs/checkpoint-postgres/langgraph/checkpoint/postgres/base.py

@@ -229,7 +229,8 @@ class BasePostgresSaver(BaseCheckpointSaver[str]):
 
     def _dump_metadata(self, metadata: CheckpointMetadata) -> str:
         serialized_metadata = self.jsonplus_serde.dumps(metadata)
-        return serialized_metadata.decode()
+        # NOTE: we're using JSON serializer (not msgpack), so we need to remove null characters before writing
+        return serialized_metadata.decode().replace("\\u0000", "")
 
     def get_next_version(self, current: Optional[str], channel: ChannelProtocol) -> str:
         if current is None:

libs/checkpoint-postgres/tests/test_async.py

@@ -101,3 +101,13 @@ class TestAsyncPostgresSaver:
             } == {"", "inner"}
 
             # TODO: test before and limit params
+
+    async def test_null_chars(self) -> None:
+        async with AsyncPostgresSaver.from_conn_string(DEFAULT_URI) as saver:
+            config = await saver.aput(
+                self.config_1, self.chkpnt_1, {"my_key": "\x00abc"}, {}
+            )
+            assert (await saver.aget_tuple(config)).metadata["my_key"] == "abc"
+            assert [c async for c in saver.alist(None, filter={"my_key": "abc"})][
+                0
+            ].metadata["my_key"] == "abc"

libs/checkpoint-postgres/tests/test_sync.py

@@ -101,3 +101,12 @@ class TestPostgresSaver:
             } == {"", "inner"}
 
             # TODO: test before and limit params
+
+    def test_null_chars(self) -> None:
+        with PostgresSaver.from_conn_string(DEFAULT_URI) as saver:
+            config = saver.put(self.config_1, self.chkpnt_1, {"my_key": "\x00abc"}, {})
+            assert saver.get_tuple(config).metadata["my_key"] == "abc"
+            assert (
+                list(saver.list(None, filter={"my_key": "abc"}))[0].metadata["my_key"]
+                == "abc"
+            )