refactor: review comments

cibuildwheel/__main__.py

@@ -67,6 +67,7 @@ def main() -> None:
     parser.add_argument(
         "--output-dir",
         type=Path,
+        default=Path(os.environ.get("CIBW_OUTPUT_DIR", "wheelhouse")),
         help="Destination folder for the wheels. Default: wheelhouse.",
     )
 
@@ -82,17 +83,18 @@ def main() -> None:
 
     parser.add_argument(
         "package_dir",
+        metavar="PACKAGE",
         default=Path("."),
         type=Path,
         nargs="?",
         help="""
-            Path to the package that you want wheels for. Must be a subdirectory
-            of the working directory. When set to a directory, the working
-            directory is still considered the 'project' and is copied into the
-            Docker container on Linux. Default: the working directory. This can
-            also be a tar.gz file - if it is, then --config-file and
-            --output-dir are relative to the current directory, and other paths
-            are relative to the expanded SDist directory.
+            Path to the package that you want wheels for. Default: the working
+            directory. Can be a directory inside the working directory, or an
+            sdist. When set to a directory, the working directory is still
+            considered the 'project' and is copied into the Docker container
+            on Linux.  When set to a tar.gz sdist file, --config-file
+            and --output-dir are relative to the current directory, and other
+            paths are relative to the expanded SDist directory.
         """,
     )
 
@@ -119,11 +121,7 @@ def main() -> None:
     args.package_dir = args.package_dir.resolve()
 
     # This are always relative to the base directory, even in SDist builds
-    args.output_dir = Path(
-        args.output_dir
-        if args.output_dir is not None
-        else os.environ.get("CIBW_OUTPUT_DIR", "wheelhouse")
-    ).resolve()
+    args.output_dir = args.output_dir.resolve()
 
     # Standard builds if a directory or non-existent path is given
     if not args.package_dir.is_file() and not args.package_dir.name.endswith("tar.gz"):

cibuildwheel/options.py

@@ -8,7 +8,7 @@ from pathlib import Path
 from typing import (
     Any,
     Dict,
-    Iterator,
+    Generator,
     List,
     Mapping,
     NamedTuple,
@@ -48,7 +48,7 @@ from .util import (
 class CommandLineArguments:
     platform: Literal["auto", "linux", "macos", "windows"]
     archs: Optional[str]
-    output_dir: Optional[Path]
+    output_dir: Path
     config_file: str
     package_dir: Path
     print_build_identifiers: bool
@@ -265,7 +265,7 @@ class OptionsReader:
         ]
 
     @contextmanager
-    def identifier(self, identifier: Optional[str]) -> Iterator[None]:
+    def identifier(self, identifier: Optional[str]) -> Generator[None, None, None]:
         self.current_identifier = identifier
         try:
             yield
@@ -363,7 +363,6 @@ class Options:
     @property
     def globals(self) -> GlobalOptions:
         args = self.command_line_arguments
-        assert args.output_dir is not None, "Must be resolved"
         package_dir = args.package_dir
         output_dir = args.output_dir