Re: [PATCH v2 02/38] qapi-gen: Separate arg-parsing from generation

[Cleber Rosa <crosa@redhat.com>]

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On Tue, Sep 22, 2020 at 05:00:25PM -0400, John Snow wrote:
> This is a minor re-work of the entrypoint script. It isolates a
> generate() method from the actual command-line mechanism.
> 
> Signed-off-by: John Snow <jsnow@redhat.com>
> ---
>  scripts/qapi-gen.py | 87 ++++++++++++++++++++++++++++++++-------------
>  1 file changed, 63 insertions(+), 24 deletions(-)
> 
> diff --git a/scripts/qapi-gen.py b/scripts/qapi-gen.py
> index 4b03f7d53b..59becba3e1 100644
> --- a/scripts/qapi-gen.py
> +++ b/scripts/qapi-gen.py
> @@ -1,9 +1,13 @@
>  #!/usr/bin/env python3
> -# QAPI generator
> -#
> +
>  # This work is licensed under the terms of the GNU GPL, version 2 or later.
>  # See the COPYING file in the top-level directory.
>  
> +"""
> +QAPI Generator
> +
> +This script is the main entry point for generating C code from the QAPI schema.
> +"""
>  
>  import argparse
>  import re
> @@ -11,21 +15,65 @@
>  
>  from qapi.commands import gen_commands
>  from qapi.doc import gen_doc
> +from qapi.error import QAPIError
>  from qapi.events import gen_events
>  from qapi.introspect import gen_introspect
> -from qapi.schema import QAPIError, QAPISchema
> +from qapi.schema import QAPISchema
>  from qapi.types import gen_types
>  from qapi.visit import gen_visit
>  
>  
> -def main(argv):
> +DEFAULT_OUTPUT_DIR = ''
> +DEFAULT_PREFIX = ''

I did not understand the purpose of these.  If they're used only as
the default value for the command line option parsing, I'd suggest
dropping them.

> +
> +
> +def generate(schema_file: str,
> +             output_dir: str,
> +             prefix: str,
> +             unmask: bool = False,
> +             builtins: bool = False) -> None:
> +    """
> +    generate uses a given schema to produce C code in the target directory.
> +
> +    :param schema_file: The primary QAPI schema file.
> +    :param output_dir: The output directory to store generated code.
> +    :param prefix: Optional C-code prefix for symbol names.
> +    :param unmask: Expose non-ABI names through introspection?
> +    :param builtins: Generate code for built-in types?
> +
> +    :raise QAPIError: On failures.
> +    """
> +    match = re.match(r'([A-Za-z_.-][A-Za-z0-9_.-]*)?', prefix)
> +    if match and match.end() != len(prefix):

Nice catch with the extra check here.  Maybe worth mentioning and/or
splitting the change?

> +        msg = "funny character '{:s}' in prefix '{:s}'".format(
> +            prefix[match.end()], prefix)
> +        raise QAPIError('', None, msg)
> +
> +    schema = QAPISchema(schema_file)
> +    gen_types(schema, output_dir, prefix, builtins)
> +    gen_visit(schema, output_dir, prefix, builtins)
> +    gen_commands(schema, output_dir, prefix)
> +    gen_events(schema, output_dir, prefix)
> +    gen_introspect(schema, output_dir, prefix, unmask)
> +    gen_doc(schema, output_dir, prefix)
> +
> +
> +def main() -> int:

One extra Pythonic touch would be to use a bool here, and then:

  sys.exit(0 if main() else 1)

But that's probably overkill.

> +    """
> +    gapi-gen shell script entrypoint.
> +    Expects arguments via sys.argv, see --help for details.
> +
> +    :return: int, 0 on success, 1 on failure.
> +    """
>      parser = argparse.ArgumentParser(
>          description='Generate code from a QAPI schema')
>      parser.add_argument('-b', '--builtins', action='store_true',
>                          help="generate code for built-in types")
> -    parser.add_argument('-o', '--output-dir', action='store', default='',
> +    parser.add_argument('-o', '--output-dir', action='store',
> +                        default=DEFAULT_OUTPUT_DIR,
>                          help="write output to directory OUTPUT_DIR")
> -    parser.add_argument('-p', '--prefix', action='store', default='',
> +    parser.add_argument('-p', '--prefix', action='store',
> +                        default=DEFAULT_PREFIX,
>                          help="prefix for symbols")
>      parser.add_argument('-u', '--unmask-non-abi-names', action='store_true',
>                          dest='unmask',
> @@ -33,26 +81,17 @@ def main(argv):
>      parser.add_argument('schema', action='store')
>      args = parser.parse_args()
>  
> -    match = re.match(r'([A-Za-z_.-][A-Za-z0-9_.-]*)?', args.prefix)
> -    if match.end() != len(args.prefix):
> -        print("%s: 'funny character '%s' in argument of --prefix"
> -              % (sys.argv[0], args.prefix[match.end()]),
> -              file=sys.stderr)
> -        sys.exit(1)
> -
>      try:
> -        schema = QAPISchema(args.schema)
> +        generate(args.schema,
> +                 output_dir=args.output_dir,
> +                 prefix=args.prefix,
> +                 unmask=args.unmask,
> +                 builtins=args.builtins)
>      except QAPIError as err:
> -        print(err, file=sys.stderr)
> -        exit(1)
> -

Glad to see that this "quitter" is gone in favor of one and only
sys.exit().

- Cleber.

> -    gen_types(schema, args.output_dir, args.prefix, args.builtins)
> -    gen_visit(schema, args.output_dir, args.prefix, args.builtins)
> -    gen_commands(schema, args.output_dir, args.prefix)
> -    gen_events(schema, args.output_dir, args.prefix)
> -    gen_introspect(schema, args.output_dir, args.prefix, args.unmask)
> -    gen_doc(schema, args.output_dir, args.prefix)
> +        print(f"{sys.argv[0]}: {str(err)}", file=sys.stderr)
> +        return 1
> +    return 0
>  
>  
>  if __name__ == '__main__':
> -    main(sys.argv)
> +    sys.exit(main())
> -- 
> 2.26.2
> 

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