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, 20 insertions, 16 deletions

diff --git a/bin/just-import-git.py b/bin/just-import-git.py
index 7416bb7b..eb3b690f 100755
--- a/bin/just-import-git.py
+++ b/bin/just-import-git.py
@@ -23,7 +23,7 @@ import tempfile
 from argparse import ArgumentParser, Namespace
 from pathlib import Path
 
-from typing import Any, Dict, Iterable, List, Optional, Set, Tuple, cast
+from typing import Any, Dict, Iterable, List, NoReturn, Optional, Set, Tuple, cast
 
 # generic JSON type that avoids getter issues; proper use is being enforced by
 # return types of methods and typing vars holding return values of json getters
@@ -34,7 +34,7 @@ def log(*args: str, **kwargs: Any) -> None:
     print(*args, file=sys.stderr, **kwargs)
 
 
-def fail(s: str, exit_code: int = 1):
+def fail(s: str, exit_code: int = 1) -> NoReturn:
     log(f"Error: {s}")
     sys.exit(exit_code)
 
@@ -114,7 +114,7 @@ def get_repository_config_file(root: Optional[str] = None) -> Optional[str]:
             return path
 
 
-def get_base_config(repository_config: Optional[str]) -> Optional[Json]:
+def get_base_config(repository_config: Optional[str]) -> Json:
     if repository_config == "-":
         return json.load(sys.stdin)
     if not repository_config:
@@ -125,9 +125,13 @@ def get_base_config(repository_config: Optional[str]) -> Optional[Json]:
     fail('Could not get base config')
 
 
-def clone(url: str, branch: str, *,
-          mirrors: List[str], inherit_env: List[str],
-          ) -> Tuple[str, Dict[str, Any], str]:
+def clone(
+    url: str,
+    branch: str,
+    *,
+    mirrors: List[str],
+    inherit_env: List[str],
+) -> Tuple[str, Dict[str, Any], str]:
     # clone the given git repository, checkout the specified
     # branch, and return the checkout location
     workdir: str = tempfile.mkdtemp()
@@ -157,7 +161,7 @@ def get_repo_to_import(config: Json) -> str:
         return cast(str, config.get("main"))
     repos = config.get("repositories", {}).keys()
     if repos:
-        return sorted(repos)[0]
+        return cast(str, sorted(repos)[0])
     fail("Config does not contain any repositories; unsure what to import")
 
 
@@ -226,8 +230,8 @@ def name_imports(to_import: List[str],
     return assign
 
 
-def rewrite_repo(repo_spec: Json, *, remote: Dict[str, Any],
-                 assign: Json, absent: bool) -> Json:
+def rewrite_repo(repo_spec: Json, *, remote: Dict[str, Any], assign: Json,
+                 absent: bool) -> Json:
     new_spec: Json = {}
     repo = repo_spec.get("repository", {})
     if isinstance(repo, str):
@@ -261,12 +265,13 @@ def rewrite_repo(repo_spec: Json, *, remote: Dict[str, Any],
 
 
 def handle_import(args: Namespace) -> Json:
-    base_config: Json = cast(Json, get_base_config(args.repository_config))
+    base_config: Json = get_base_config(args.repository_config)
     base_repos: Json = base_config.get("repositories", {})
     srcdir, remote, to_cleanup = clone(
-        args.URL, args.branch,
-        mirrors = args.mirrors,
-        inherit_env = args.inherit_env,
+        args.URL,
+        args.branch,
+        mirrors=args.mirrors,
+        inherit_env=args.inherit_env,
     )
     if args.foreign_repository_config:
         foreign_config_file = args.foreign_repository_config
@@ -293,7 +298,7 @@ def handle_import(args: Namespace) -> Json:
             fail('Could not get repository config file')
     foreign_repos: Json = foreign_config.get("repositories", {})
     if args.foreign_repository_name:
-        foreign_name = args.foreign_repository_name
+        foreign_name = cast(str, args.foreign_repository_name)
     else:
         foreign_name = get_repo_to_import(foreign_config)
     import_map: Json = {}
@@ -357,8 +362,7 @@ def main():
     parser.add_argument(
         "--absent",
         action="store_true",
-        help="Import repository and all its dependencies as absent."
-    )
+        help="Import repository and all its dependencies as absent.")
     parser.add_argument(
         "--as",
         dest="import_as",