Require runnable dispatcher subcommands (#1585)

* Require runnable dispatcher subcommands

* Use modern dispatcher test loader

scripts/odysseus

@@ -68,6 +68,10 @@ def _short_help(path: Path) -> str:
     return first
 
 
+def _is_runnable_subcommand(path: Path) -> bool:
+    return path.exists() and path.is_file() and os.access(path, os.X_OK)
+
+
 def _print_listing() -> None:
     """`odysseus` with no args (or `odysseus help`) — print the table."""
     sys.stdout.write(f"odysseus {VERSION} — every feature, on the shell.\n\n")
@@ -101,7 +105,7 @@ def main(argv: list[str] | None = None) -> int:
             _print_listing()
             return 0
         sub = SCRIPTS_DIR / f"odysseus-{argv[1]}"
-        if not sub.exists():
+        if not _is_runnable_subcommand(sub):
             sys.stderr.write(f"odysseus: unknown subcommand {argv[1]!r}\n")
             return 1
         return subprocess.call([str(sub), "--help"])
@@ -109,7 +113,7 @@ def main(argv: list[str] | None = None) -> int:
     # `odysseus foo ...` → exec `odysseus-foo ...` under the project venv.
     name = argv[0]
     sub = SCRIPTS_DIR / f"odysseus-{name}"
-    if not sub.exists():
+    if not _is_runnable_subcommand(sub):
         sys.stderr.write(
             f"odysseus: unknown subcommand {name!r}. "
             f"Try `odysseus help` to see available ones.\n"

tests/test_odysseus_dispatcher.py

@@ -0,0 +1,24 @@
+import importlib.machinery
+import importlib.util
+from pathlib import Path
+
+
+def _load_dispatcher():
+    path = Path(__file__).resolve().parent.parent / "scripts" / "odysseus"
+    loader = importlib.machinery.SourceFileLoader("odysseus_dispatcher_under_test", str(path))
+    spec = importlib.util.spec_from_loader(loader.name, loader)
+    module = importlib.util.module_from_spec(spec)
+    loader.exec_module(module)
+    return module
+
+
+def test_is_runnable_subcommand_requires_executable_file(tmp_path):
+    cli = _load_dispatcher()
+    sub = tmp_path / "odysseus-demo"
+    sub.write_text("#!/bin/sh\n")
+    sub.chmod(0o644)
+
+    assert cli._is_runnable_subcommand(sub) is False
+
+    sub.chmod(0o755)
+    assert cli._is_runnable_subcommand(sub) is True