bin scripts: Use the NoReturn type hint

The NoReturn type hint should be used to ensure the return type of
methods calling no-return methods are not falsely enforced to an
Optional return type.

Add the NoReturn type hint as needed and clear up existing Optional
returns together with any corresponding casts affected by the
above.

While there, also fix formatting.

1 files changed, 7 insertions, 7 deletions

diff --git a/bin/bootstrap-traverser.py b/bin/bootstrap-traverser.py
index 9b82b338..1598c842 100755
--- a/bin/bootstrap-traverser.py
+++ b/bin/bootstrap-traverser.py
@@ -19,7 +19,7 @@ import os
 import shutil
 import subprocess
 import sys
-from typing import Any, Dict, List, Optional, cast
+from typing import Any, Dict, List, NoReturn, cast
 
 from argparse import ArgumentParser
 
@@ -32,7 +32,7 @@ def log(*args: str, **kwargs: Any) -> None:
     print(*args, file=sys.stderr, **kwargs)
 
 
-def fail(s: str) -> None:
+def fail(s: str) -> NoReturn:
     log(s)
     sys.exit(1)
 
@@ -66,7 +66,7 @@ def link(src: str, dest: str) -> None:
         os.symlink(src, dest)
 
 
-def build_local(desc: Json, *, root: str, config: Json) -> Optional[str]:
+def build_local(desc: Json, *, root: str, config: Json) -> str:
     repo_name = desc["data"]["repository"]
     repo: List[str] = config["repositories"][repo_name]["workspace_root"]
     rel_path = desc["data"]["path"]
@@ -83,7 +83,7 @@ def build_tree(desc: Json, *, config: Json, root: str, graph: Json) -> str:
     tree_dir_tmp = tree_dir + ".tmp"
     tree_desc = graph["trees"][tree_id]
     for location, desc in tree_desc.items():
-        link(cast(str, build(desc, config=config, root=root, graph=graph)),
+        link(build(desc, config=config, root=root, graph=graph),
              os.path.join(tree_dir_tmp, location))
     # correctly handle the empty tree
     os.makedirs(tree_dir_tmp, exist_ok=True)
@@ -98,7 +98,7 @@ def run_action(action_id: str, *, config: Json, root: str, graph: Json) -> str:
     os.makedirs(action_dir)
     action_desc = graph["actions"][action_id]
     for location, desc in action_desc.get("input", {}).items():
-        link(cast(str, build(desc, config=config, root=root, graph=graph)),
+        link(build(desc, config=config, root=root, graph=graph),
              os.path.join(action_dir, location))
     cmd = action_desc["command"]
     env = action_desc.get("env")
@@ -121,7 +121,7 @@ def build_action(desc: Json, *, config: Json, root: str, graph: Json) -> str:
     return os.path.join(action_dir, desc["data"]["path"])
 
 
-def build(desc: Json, *, config: Json, root: str, graph: Json) -> Optional[str]:
+def build(desc: Json, *, config: Json, root: str, graph: Json) -> str:
     if desc["type"] == "TREE":
         return build_tree(desc, config=config, root=root, graph=graph)
     if desc["type"] == "ACTION":
@@ -139,7 +139,7 @@ def traverse(*, graph: Json, to_build: Json, out: str, root: str,
     os.makedirs(root, exist_ok=True)
     create_blobs(graph["blobs"], root=root)
     for location, artifact in to_build.items():
-        link(cast(str, build(artifact, config=config, root=root, graph=graph)),
+        link(build(artifact, config=config, root=root, graph=graph),
              os.path.join(out, location))