[libc] Use idiomatic main() function in newhdrgen/yaml_to_classes.py (llvm#113419)

This changes the entry-point Python script of newhdrgen to use
the idiomatic main() function of no arguments that does the whole
job of the script.  This replaces the unusual pattern of having
an idiosyncratic main(...) signature and having the script's
direct code do argument parsing outside the main function.  The
idiomatic pattern makes it possible to usefully wrap the script
in Python and still use its full command-line functionality.

Author: frobtech

libc/newhdrgen/yaml_to_classes.py

@@ -216,52 +216,7 @@ def increase_indent(self, flow=False, indentless=False):
     print(f"Added function {new_function.name} to {yaml_file}")
 
 
-def main(
-    yaml_file,
-    output_dir=None,
-    h_def_file=None,
-    add_function=None,
-    entry_points=None,
-    export_decls=False,
-):
-    """
-    Main function to generate header files from YAML and .h.def templates.
-
-    Args:
-        yaml_file: Path to the YAML file containing header specification.
-        h_def_file: Path to the .h.def template file.
-        output_dir: Directory to output the generated header file.
-        add_function: Details of the function to be added to the YAML file (if any).
-        entry_points: A list of specific function names to include in the header.
-        export_decls: Flag to use GpuHeader for exporting declarations.
-    """
-    if add_function:
-        add_function_to_yaml(yaml_file, add_function)
-
-    header_class = GpuHeader if export_decls else HeaderFile
-    header = load_yaml_file(yaml_file, header_class, entry_points)
-
-    header_str = str(header)
-
-    if output_dir:
-        output_file_path = Path(output_dir)
-        if output_file_path.is_dir():
-            output_file_path /= f"{Path(yaml_file).stem}.h"
-    else:
-        output_file_path = Path(f"{Path(yaml_file).stem}.h")
-
-    if not export_decls and h_def_file:
-        with open(h_def_file, "r") as f:
-            h_def_content = f.read()
-        final_header_content = fill_public_api(header_str, h_def_content)
-        with open(output_file_path, "w") as f:
-            f.write(final_header_content)
-    else:
-        with open(output_file_path, "w") as f:
-            f.write(header_str)
-
-
-if __name__ == "__main__":
+def main():
     parser = argparse.ArgumentParser(description="Generate header files from YAML")
     parser.add_argument(
         "yaml_file", help="Path to the YAML file containing header specification"
@@ -297,11 +252,31 @@ def main(
     )
     args = parser.parse_args()
 
-    main(
-        args.yaml_file,
-        args.output_dir,
-        args.h_def_file,
-        args.add_function,
-        args.entry_points,
-        args.export_decls,
-    )
+    if args.add_function:
+        add_function_to_yaml(yaml_file, args.add_function)
+
+    header_class = GpuHeader if args.export_decls else HeaderFile
+    header = load_yaml_file(args.yaml_file, header_class, args.entry_points)
+
+    header_str = str(header)
+
+    if args.output_dir:
+        output_file_path = Path(args.output_dir)
+        if output_file_path.is_dir():
+            output_file_path /= f"{Path(args.yaml_file).stem}.h"
+    else:
+        output_file_path = Path(f"{Path(args.yaml_file).stem}.h")
+
+    if not args.export_decls and args.h_def_file:
+        with open(args.h_def_file, "r") as f:
+            h_def_content = f.read()
+        final_header_content = fill_public_api(header_str, h_def_content)
+        with open(output_file_path, "w") as f:
+            f.write(final_header_content)
+    else:
+        with open(output_file_path, "w") as f:
+            f.write(header_str)
+
+
+if __name__ == "__main__":
+    main()