project: add NIAR_WORKING_DIRECTORY support.

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## 0.1.3 (unreleased)
 
+New:
+
+* project: `NIAR_WORKING_DIRECTORY` can be used to override the origin.
+
 ## 0.1.2
 
 New:

src/niar/project.py

@@ -1,3 +1,4 @@
+import os
 import sys
 from pathlib import Path
 from typing import Optional
@@ -100,16 +101,21 @@ class Project:
     ]
 
     def __init_subclass__(cls):
-        # We expect to be called from project-root/module/__init.py__ or similar;
-        # cls.origin is project-root. Keep going up until we find pyproject.toml.
-        origin = Path(sys._getframe(1).f_code.co_filename).absolute().parent
-        while True:
-            if (origin / "pyproject.toml").is_file():
-                cls.origin = origin
-                break
-            if not any(origin.parents):
-                assert False, "could not find pyproject.toml"
-            origin = origin.parent
+        if origin := os.getenv("NIAR_WORKING_DIRECTORY"):
+            cls.origin = Path(origin).absolute()
+        else:
+            # We expect to be called from project-root/module/__init.py__ or similar;
+            # cls.origin is project-root. Keep going up until we find pyproject.toml.
+            origin = Path(sys._getframe(1).f_code.co_filename).absolute().parent
+            while True:
+                if (origin / "pyproject.toml").is_file():
+                    cls.origin = origin
+                    break
+                if not any(origin.parents):
+                    assert False, "could not find pyproject.toml"
+                origin = origin.parent
+
+        os.chdir(cls.origin)
 
         extras = cls.__dict__.keys() - {"__module__", "__doc__", "origin"}
         for prop in cls.PROPS: