Guard deploy.py behind __main__; test that import has no side effects

deploy.py

@@ -1,12 +1,24 @@
+"""Manual build-and-upload helper. Importing this module has no side effects.
+
+Run it explicitly (``python deploy.py``) to build and upload to PyPI. CI (wads)
+normally publishes releases, so this is only a manual fallback.
+"""
+
 import subprocess
+import sys
+
+BUILD_COMMAND = (sys.executable, "setup.py", "sdist", "bdist_wheel")
+UPLOAD_COMMAND = (sys.executable, "-m", "twine", "upload", "dist/*")
+
+
+def main():
+    # TODO: Both of these are python. Change to use python objects directly.
+    print("--------------------------- setup_output ---------------------------")
+    subprocess.run(BUILD_COMMAND)
 
-# # TODO: Both of these are python. Change to use python objects directly.
-print("--------------------------- setup_output ---------------------------")
-setup_output = subprocess.run("python setup.py sdist bdist_wheel".split(" "))
-# print(f"{setup_output}\n")
+    print("--------------------------- upload_output ---------------------------")
+    subprocess.run(UPLOAD_COMMAND)
 
-print("--------------------------- upload_output ---------------------------")
-upload_output = subprocess.run("python -m twine upload dist/*".split(" "))
-# print(f"{upload_output.decode()}\n")
 
-# import twine
+if __name__ == "__main__":
+    main()

tests/test_deploy_import.py

@@ -0,0 +1,20 @@
+"""Importing the repo-root ``deploy.py`` must not build or upload anything."""
+
+import importlib.util
+import subprocess
+from pathlib import Path
+
+DEPLOY_PATH = Path(__file__).resolve().parent.parent / "deploy.py"
+
+
+def test_importing_deploy_has_no_side_effects(monkeypatch):
+    calls = []
+    monkeypatch.setattr(subprocess, "run", lambda *a, **kw: calls.append(a))
+    monkeypatch.setattr(subprocess, "Popen", lambda *a, **kw: calls.append(a))
+
+    spec = importlib.util.spec_from_file_location("_deploy_under_test", DEPLOY_PATH)
+    module = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(module)
+
+    assert calls == []
+    assert callable(module.main)