Set up the bones of a Flask app with configuration

src/config/__init__.py

@@ -0,0 +1,38 @@
+import json
+from logging import INFO
+from dataclasses import dataclass
+from typing import Any
+
+from .logging import Logging
+from .parse import ConfigParseError, assert_key_of_type
+
+
+@dataclass
+class Config:
+    host: str | None
+    port: int | None
+    logging: Logging
+
+    @classmethod
+    def from_dict(cls, config: dict[str, Any]) -> 'Config':
+        assert_key_of_type(config, 'logging', dict)
+        assert_key_of_type(config, 'host', str)
+        assert_key_of_type(config, 'port', int)
+        try:
+            log_config = Logging.from_dict(config['logging'])
+            return Config(host=config['host'], port=config['port'], logging=log_config)
+
+        except ConfigParseError as e:
+            raise ConfigParseError(['logging', *e.keypath], e.issue) from e
+
+
+DEFAULT_CONFIG = Config(logging=Logging(level=INFO), port=None, host=None)
+
+
+def parse_config(filename: str) -> Config:
+    with open(filename, 'r') as infile:
+        config = json.loads(infile.read())
+    return Config.from_dict(config)
+
+
+__all__ = ['Config', 'parse_config', 'DEFAULT_CONFIG']