Avoid de/recode of bytes to string to bytes when writing json files (#109348)

homeassistant/helpers/json.py

@@ -148,12 +148,17 @@ JSON_DUMP: Final = json_dumps
 
 
 def _orjson_default_encoder(data: Any) -> str:
-    """JSON encoder that uses orjson with hass defaults."""
+    """JSON encoder that uses orjson with hass defaults and returns a str."""
+    return _orjson_bytes_default_encoder(data).decode("utf-8")
+
+
+def _orjson_bytes_default_encoder(data: Any) -> bytes:
+    """JSON encoder that uses orjson with hass defaults and returns bytes."""
     return orjson.dumps(
         data,
         option=orjson.OPT_INDENT_2 | orjson.OPT_NON_STR_KEYS,
         default=json_encoder_default,
-    ).decode("utf-8")
+    )
 
 
 def save_json(
@@ -173,11 +178,13 @@ def save_json(
         if encoder and encoder is not JSONEncoder:
             # If they pass a custom encoder that is not the
             # default JSONEncoder, we use the slow path of json.dumps
+            mode = "w"
             dump = json.dumps
-            json_data = json.dumps(data, indent=2, cls=encoder)
+            json_data: str | bytes = json.dumps(data, indent=2, cls=encoder)
         else:
+            mode = "wb"
             dump = _orjson_default_encoder
-            json_data = _orjson_default_encoder(data)
+            json_data = _orjson_bytes_default_encoder(data)
     except TypeError as error:
         formatted_data = format_unserializable_data(
             find_paths_unserializable_data(data, dump=dump)
@@ -186,10 +193,8 @@ def save_json(
         _LOGGER.error(msg)
         raise SerializationError(msg) from error
 
-    if atomic_writes:
-        write_utf8_file_atomic(filename, json_data, private)
-    else:
-        write_utf8_file(filename, json_data, private)
+    method = write_utf8_file_atomic if atomic_writes else write_utf8_file
+    method(filename, json_data, private, mode=mode)
 
 
 def find_paths_unserializable_data(

homeassistant/util/file.py

@@ -17,9 +17,7 @@ class WriteError(HomeAssistantError):
 
 
 def write_utf8_file_atomic(
-    filename: str,
-    utf8_data: str,
-    private: bool = False,
+    filename: str, utf8_data: bytes | str, private: bool = False, mode: str = "w"
 ) -> None:
     """Write a file and rename it into place using atomicwrites.
 
@@ -34,7 +32,7 @@ def write_utf8_file_atomic(
     negatively impact performance.
     """
     try:
-        with AtomicWriter(filename, overwrite=True).open() as fdesc:
+        with AtomicWriter(filename, mode=mode, overwrite=True).open() as fdesc:
             if not private:
                 os.fchmod(fdesc.fileno(), 0o644)
             fdesc.write(utf8_data)
@@ -44,20 +42,18 @@ def write_utf8_file_atomic(
 
 
 def write_utf8_file(
-    filename: str,
-    utf8_data: str,
-    private: bool = False,
+    filename: str, utf8_data: bytes | str, private: bool = False, mode: str = "w"
 ) -> None:
     """Write a file and rename it into place.
 
     Writes all or nothing.
     """
-
     tmp_filename = ""
+    encoding = "utf-8" if "b" not in mode else None
     try:
         # Modern versions of Python tempfile create this file with mode 0o600
         with tempfile.NamedTemporaryFile(
-            mode="w", encoding="utf-8", dir=os.path.dirname(filename), delete=False
+            mode=mode, encoding=encoding, dir=os.path.dirname(filename), delete=False
         ) as fdesc:
             fdesc.write(utf8_data)
             tmp_filename = fdesc.name

tests/util/test_file.py

@@ -25,6 +25,11 @@ def test_write_utf8_file_atomic_private(tmpdir: py.path.local, func) -> None:
         assert fh.read() == '{"some":"data"}'
     assert os.stat(test_file).st_mode & 0o777 == 0o600
 
+    func(test_file, b'{"some":"data"}', True, mode="wb")
+    with open(test_file) as fh:
+        assert fh.read() == '{"some":"data"}'
+    assert os.stat(test_file).st_mode & 0o777 == 0o600
+
 
 def test_write_utf8_file_fails_at_creation(tmpdir: py.path.local) -> None:
     """Test that failed creation of the temp file does not create an empty file."""