Fix type errors

src/py/flwr/server/superlink/ffs/disk_ffs.py

@@ -24,14 +24,14 @@
 
 def write_dict_to_file(data_dict: Dict[str, str], file_path: str) -> None:
     """Write a Dict to a file in JSON format."""
-    with open(file_path, "w") as file:
+    with open(file_path, "w", encoding="utf-8") as file:
         json.dump(data_dict, file)
 
 
 def read_dict_from_file(file_path: str) -> Dict[str, str]:
     """Read a Dict from a JSON file."""
-    with open(file_path) as file:
-        data_dict = json.load(file)
+    with open(file_path, encoding="utf-8") as file:
+        data_dict: Dict[str, str] = json.load(file)
     return data_dict
 
 

src/py/flwr/server/superlink/ffs/ffs_test.py

@@ -21,6 +21,7 @@
 import tempfile
 import unittest
 from abc import abstractmethod
+from typing import Dict
 
 from flwr.server.superlink.ffs import DiskFfs, Ffs
 
@@ -31,6 +32,8 @@ class FfsTest(unittest.TestCase):
     # This is to True in each child class
     __test__ = False
 
+    tmp_dir: tempfile.TemporaryDirectory  # type: ignore
+
     @abstractmethod
     def ffs_factory(self) -> Ffs:
         """Provide Ffs implementation to test."""
@@ -60,13 +63,15 @@ def test_get(self) -> None:
         ffs: Ffs = self.ffs_factory()
         content_expected = b"content"
         hash_expected = hashlib.sha256(content_expected).hexdigest()
-        meta_expected = {}
+        meta_expected: Dict[str, str] = {"meta_key": "meta_value"}
 
         with open(os.path.join(self.tmp_dir.name, hash_expected), "wb") as file:
             file.write(content_expected)
 
         with open(
-            os.path.join(self.tmp_dir.name, f"{hash_expected}.META"), "w"
+            os.path.join(self.tmp_dir.name, f"{hash_expected}.META"),
+            "w",
+            encoding="utf-8",
         ) as file:
             json.dump(meta_expected, file)
 
@@ -83,13 +88,15 @@ def test_delete(self) -> None:
         ffs: Ffs = self.ffs_factory()
         content_expected = b"content"
         hash_expected = hashlib.sha256(content_expected).hexdigest()
-        meta_expected = {}
+        meta_expected: Dict[str, str] = {"meta_key": "meta_value"}
 
         with open(os.path.join(self.tmp_dir.name, hash_expected), "wb") as file:
             file.write(content_expected)
 
         with open(
-            os.path.join(self.tmp_dir.name, f"{hash_expected}.META"), "w"
+            os.path.join(self.tmp_dir.name, f"{hash_expected}.META"),
+            "w",
+            encoding="utf-8",
         ) as file:
             json.dump(meta_expected, file)
 
@@ -105,13 +112,15 @@ def test_list(self) -> None:
         ffs: Ffs = self.ffs_factory()
         content_expected = b"content"
         hash_expected = hashlib.sha256(content_expected).hexdigest()
-        meta_expected = {}
+        meta_expected: Dict[str, str] = {"meta_key": "meta_value"}
 
         with open(os.path.join(self.tmp_dir.name, hash_expected), "wb") as file:
             file.write(content_expected)
 
         with open(
-            os.path.join(self.tmp_dir.name, f"{hash_expected}.META"), "w"
+            os.path.join(self.tmp_dir.name, f"{hash_expected}.META"),
+            "w",
+            encoding="utf-8",
         ) as file:
             json.dump(meta_expected, file)