core: move stuff from tests/demo.py to my/core/tests/test_config.py

also clean all this up a bit

my/demo.py

@@ -2,19 +2,23 @@
 Just a demo module for testing and documentation purposes
 '''
 
-from .core import Paths, PathIsh
-
-from typing import Optional
-from datetime import tzinfo, timezone
-
-from my.config import demo as user_config
+import json
+from abc import abstractmethod
 from dataclasses import dataclass
+from datetime import datetime, timezone, tzinfo
+from pathlib import Path
+from typing import Iterable, Optional, Protocol, Sequence
+
+from my.core import Json, PathIsh, Paths, get_files
 
 
-@dataclass
-class demo(user_config):
+class config(Protocol):
     data_path: Paths
+
+    # this is to check required attribute handling
     username: str
+
+    # this is to check optional attribute handling
     timezone: tzinfo = timezone.utc
 
     external: Optional[PathIsh] = None
@@ -23,47 +27,50 @@ class demo(user_config):
     def external_module(self):
         rpath = self.external
         if rpath is not None:
-            from .core.utils.imports import import_dir
+            from my.core.utils.imports import import_dir
+
             return import_dir(rpath)
 
-        import my.config.repos.external as m # type: ignore
+        import my.config.repos.external as m  # type: ignore
+
         return m
 
 
-from .core import make_config
-config = make_config(demo)
+def make_config() -> config:
+    from my.config import demo as user_config
 
-# TODO not sure about type checking?
-external = config.external_module
+    class combined_config(user_config, config): ...
 
+    return combined_config()
 
-from pathlib import Path
-from typing import Sequence, Iterable
-from datetime import datetime
-from .core import Json, get_files
 
 @dataclass
 class Item:
     '''
     Some completely arbitrary artificial stuff, just for testing
     '''
+
     username: str
     raw: Json
     dt: datetime
 
 
 def inputs() -> Sequence[Path]:
-    return get_files(config.data_path)
+    cfg = make_config()
+    return get_files(cfg.data_path)
 
 
-import json
 def items() -> Iterable[Item]:
+    cfg = make_config()
+
+    transform = (lambda i: i) if cfg.external is None else cfg.external_module.transform
+
     for f in inputs():
-        dt = datetime.fromtimestamp(f.stat().st_mtime, tz=config.timezone)
+        dt = datetime.fromtimestamp(f.stat().st_mtime, tz=cfg.timezone)
         j = json.loads(f.read_text())
         for raw in j:
             yield Item(
-                username=config.username,
-                raw=external.identity(raw),
+                username=cfg.username,
+                raw=transform(raw),
                 dt=dt,
             )