autocal layout first design

shared/src/orisys_app_shared/paths.py

@@ -1,34 +1,80 @@
-"""Resolve app, config, and output paths for editable and frozen runs."""
+"""Resolve app, config, and output paths for editable and frozen runs.
+
+Several desktop products share this package. Which one a process belongs to is
+decided once, at start-up:
+
+* ``ORISYS_APP_ID`` — the directory name under ``apps/`` (e.g. ``studio``,
+  ``autocal``). Set it **before** importing anything from this package; an app
+  that changes it later gets whichever root was resolved first, because these
+  helpers are called during import of logging/prefs.
+* Otherwise the historic behaviour applies, which resolves ``apps/studio``.
+  That keeps existing callers working without them passing anything.
+"""
 
 from __future__ import annotations
 
+import os
 import sys
 from pathlib import Path
 
+#: Environment variable naming the app directory under ``apps/``.
+APP_ID_ENV = "ORISYS_APP_ID"
+
+#: Fallback app when ``ORISYS_APP_ID`` is unset — the first product built here.
+DEFAULT_APP_ID = "studio"
+
 
 def is_frozen() -> bool:
     return bool(getattr(sys, "frozen", False))
 
 
-def _studio_root_from_shared() -> Path:
-    """Repo layout: shared/src/orisys_app_shared -> apps/studio."""
+def app_id() -> str:
+    """The app directory name for this process."""
+    return os.environ.get(APP_ID_ENV, "").strip() or DEFAULT_APP_ID
+
+
+def apps_dir() -> Path:
+    """The ``apps/`` directory of the source tree."""
     here = Path(__file__).resolve()
-    # .../orisys-app/shared/src/orisys_app_shared/paths.py
+    # .../orisys-app/shared/src/orisys_app_shared/paths.py -> .../orisys-app
     repo_root = here.parents[3]
-    return repo_root / "apps" / "studio"
+    return repo_root / "apps"
+
+
+def _default_app_root_from_shared(app_id_value: str) -> Path:
+    """Repo layout: shared/src/orisys_app_shared -> apps/<app>."""
+    return apps_dir() / app_id_value
 
 
 def app_root() -> Path:
-    """Return the studio app root (editable) or EXE directory (frozen)."""
+    """Return this app's root (editable) or the EXE directory (frozen)."""
     if is_frozen():
         return Path(sys.executable).resolve().parent
-    # Prefer cwd override when launched from apps/studio
+
+    wanted = app_id()
+
+    # Launched from inside an app directory (``python apps/<app>/run.py``).
     cwd = Path.cwd().resolve()
     if (cwd / "config").is_dir() and (cwd / "run.py").is_file():
         return cwd
-    if (cwd / "apps" / "studio" / "config").is_dir():
-        return cwd / "apps" / "studio"
-    return _studio_root_from_shared()
+
+    # Launched from the repo root.
+    candidate = cwd / "apps" / wanted
+    if (candidate / "config").is_dir():
+        return candidate
+
+    # A named app that is not where we expected must not silently fall back to
+    # another product's config: that would write one app's preferences into
+    # another's tree.
+    if wanted == DEFAULT_APP_ID:
+        return _default_app_root_from_shared(wanted)
+    unresolved = _default_app_root_from_shared(wanted)
+    if (unresolved / "config").is_dir():
+        return unresolved
+    raise FileNotFoundError(
+        f"{APP_ID_ENV}={wanted!r} does not name an app with a config directory "
+        f"(looked in {cwd / 'apps' / wanted} and {unresolved})"
+    )
 
 
 def config_dir() -> Path: