fix(lambda): expose interactions.handler on the bootstrap stub (#59)

slack_interactions is configured for interactions.handler. A recreate that
reloads the stub zip must return 503 instead of failing at init.

terraform/bootstrap/stub/handler.py

@@ -1,4 +1,8 @@
-"""Bootstrap stub. GitHub Actions replaces this zip via update-function-code."""
+"""Bootstrap stub. GitHub Actions replaces this zip via update-function-code.
+
+Keep a module for every Lambda handler setting in locals.functions. A recreate
+must return 503 instead of failing at init because the entrypoint is missing.
+"""
 
 
 def handler(event, context):

terraform/bootstrap/stub/interactions.py

@@ -0,0 +1,5 @@
+"""Alias so slack_interactions (interactions.handler) can load the stub zip."""
+
+from handler import handler
+
+__all__ = ["handler"]

tests/test_bootstrap_stub.py

@@ -0,0 +1,34 @@
+"""Stub zip must expose every Lambda handler name in locals.functions."""
+
+from __future__ import annotations
+
+import importlib.util
+import sys
+from pathlib import Path
+
+STUB_DIR = Path(__file__).resolve().parents[1] / "terraform" / "bootstrap" / "stub"
+
+
+def _load_file(module_name: str, path: Path):
+    spec = importlib.util.spec_from_file_location(module_name, path)
+    assert spec is not None and spec.loader is not None
+    module = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(module)
+    return module
+
+
+def test_stub_handler_modules_return_503() -> None:
+    handler_mod = _load_file("apm_stub_handler", STUB_DIR / "handler.py")
+    saved_handler = sys.modules.get("handler")
+    sys.modules["handler"] = handler_mod
+    try:
+        interactions_mod = _load_file("apm_stub_interactions", STUB_DIR / "interactions.py")
+        for module in (handler_mod, interactions_mod):
+            result = module.handler({}, None)
+            assert result["statusCode"] == 503
+            assert "NOT_DEPLOYED" in result["body"]
+    finally:
+        if saved_handler is None:
+            sys.modules.pop("handler", None)
+        else:
+            sys.modules["handler"] = saved_handler