Error checking inside argparse

Author: orlandoisepic

precicecasegenerate/cli.py

@@ -22,10 +22,10 @@ def makeGenerateParser(add_help: bool = True) -> argparse.ArgumentParser:
     )
     parser.add_argument(
         "input_file",
-        type=Path,
+        type=cli_helper.yaml_file,
         nargs="?",
         help="Path to the input YAML topology file.",
-        default=Path(cli_helper.DEFAULT_TOPOLOGY_NAME)
+        default=cli_helper.DEFAULT_TOPOLOGY_NAME # Needs to be a string to cover the case no input is given
     )
     parser.add_argument(
         "-v", "--verbose", action="store_true", help="Enable verbose logging output."
@@ -42,10 +42,6 @@ def runGenerate(args: argparse.Namespace) -> int:
     setup_logging(verbose=args.verbose)
     logger.info("Program started.")
 
-    return_value: int = cli_helper.validate_args(args)
-    if return_value != 0:
-        return return_value
-
     input_file: Path = Path(args.input_file)
     output_root: Path = Path(args.output_path)
 
@@ -117,6 +113,7 @@ def main() -> int:
     # Parse the command line arguments
     parser = makeGenerateParser()
     args = parser.parse_args()
+    logger.debug(f"Arguments parsed. Arguments: {vars(args)}.")
     return runGenerate(args)
 
 

precicecasegenerate/cli_helper.py

@@ -11,31 +11,28 @@
 PRECICE_CONFIG_FILE_NAME: str = "precice-config.xml"
 GENERATED_DIR_NAME: str = "_generated"
 LOG_DIR_NAME: str = ".logs"
-DEFAULT_TOPOLOGY_NAME:str = "topology.yaml"
+DEFAULT_TOPOLOGY_NAME: str = "topology.yaml"
 
 
-
-def validate_args(args: argparse.Namespace) -> int:
+def yaml_file(filepath: str) -> Path:
     """
-    Validate the arguments passed to the CLI.
-    This checks if the input file exists and is a YAML file.
-    :param args: The parsed arguments.
-    :return: 0 if the arguments are valid, 1 otherwise.
+    Check if the filepath points to an existing YAML file.
+    Otherwise, raise an argparse.ArgumentTypeError.
+    :param filepath: The path to the input file as a string.
+    :return: The path to the input file as a Path object.
     """
-    logger.debug(f"Arguments parsed. Arguments: {vars(args)}. Checking if given file exists.")
-
-    input_file: Path = Path(args.input_file).resolve()
+    input_file = Path(filepath).resolve()
 
     # Check if the file exists
     if not input_file.is_file():
         logger.critical(f"File {input_file.resolve()} does not exist. Aborting program.")
-        return 1
+        raise argparse.ArgumentTypeError(f"File '{input_file.resolve()}' does not exist.")
     logger.debug(f"File {input_file.resolve()} exists.")
 
     # Check if the file is a YAML file
-    if input_file.suffix.lower() in [".yaml", ".yml"]:
-        logger.debug(f"File {input_file.resolve()} is a YAML file.")
-    else:
+    if input_file.suffix.lower() not in [".yaml", ".yml"]:
         logger.critical(f"File {input_file.resolve()} is not a YAML file. Aborting program.")
-        return 1
-    return 0
+        raise argparse.ArgumentTypeError(f"The file '{input_file}' is not a YAML file.")
+    logger.debug(f"File {input_file.resolve()} is a YAML file.")
+
+    return input_file