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bh=PbdgrKzUBg2lo4DEn0w8O5bpjSgWWrpQawN5LJKU92Y=; b=KXRiw0Pn/tnXC1USBAwLyY2TwtYzwJCF07a+nqbzH3d176PmqJXjCc6QieeVz62MH70QVr WTfatV+7B4ikF5z2G1GXHq1tHK/6GpcvyLQZJDNMVT/WpfLASphWS0KatpCBOh7OaTEEGH gVyihVcK1w192jOKnw6TwuGJALPXTn8= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-23-Jtd3PNr-OhaTY7fpAus00w-1; Wed, 07 Oct 2020 10:53:03 -0400 X-MC-Unique: Jtd3PNr-OhaTY7fpAus00w-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2E5FB1019632 for ; Wed, 7 Oct 2020 14:53:02 +0000 (UTC) Received: from [10.10.120.38] (ovpn-120-38.rdu2.redhat.com [10.10.120.38]) by smtp.corp.redhat.com (Postfix) with ESMTP id A8E251002EEA; Wed, 7 Oct 2020 14:52:55 +0000 (UTC) Subject: Re: [PATCH v5 03/36] qapi-gen: Separate arg-parsing from generation To: Markus Armbruster References: <20201005195158.2348217-1-jsnow@redhat.com> <20201005195158.2348217-4-jsnow@redhat.com> <87imbntvw9.fsf@dusky.pond.sub.org> <69effb8e-3d83-a2e7-c484-feea8ed850b9@redhat.com> <87h7r6jws4.fsf@dusky.pond.sub.org> From: John Snow Message-ID: <65c2a120-e29e-b572-680a-ee6d141ff9c8@redhat.com> Date: Wed, 7 Oct 2020 10:52:54 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <87h7r6jws4.fsf@dusky.pond.sub.org> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jsnow@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=jsnow@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/10/07 00:54:30 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.742, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Cleber Rosa , qemu-devel@nongnu.org, Eduardo Habkost Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 10/7/20 3:54 AM, Markus Armbruster wrote: > John Snow writes: > >> On 10/6/20 7:51 AM, Markus Armbruster wrote: >>> John Snow writes: >>> >>>> 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 >>>> Reviewed-by: Eduardo Habkost >>>> Reviewed-by: Cleber Rosa >>>> Tested-by: Cleber Rosa >>>> --- >>>> scripts/qapi-gen.py | 85 +++++++++++++++++++++++++++++++++------------ >>>> 1 file changed, 62 insertions(+), 23 deletions(-) >>>> >>>> diff --git a/scripts/qapi-gen.py b/scripts/qapi-gen.py >>>> index 541e8c1f55d..117b396a595 100644 >>>> --- a/scripts/qapi-gen.py >>>> +++ b/scripts/qapi-gen.py >>>> @@ -1,30 +1,77 @@ >>>> #!/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 >>>> import sys >>>> from qapi.commands import gen_commands >>>> +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 >>> Unrelated cleanup. Okay. >>> >>>> >>>> -def main(argv): >>>> +DEFAULT_OUTPUT_DIR = '' >>>> +DEFAULT_PREFIX = '' >>>> + >>>> + >>>> +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.end() != len(prefix): >>>> + msg = "funny character '{:s}' in prefix '{:s}'".format( >>>> + prefix[match.end()], prefix) >>>> + raise QAPIError('', None, msg) >>> Uh... >>> $ python3 scripts/qapi-gen.py --prefix=@ x >>> scripts/qapi-gen.py: : funny character '@' in prefix '@' >>> Unwanted " :". >>> This is due to a hack: you pass '' for info (*quack*). Everything >>> else >>> passes QAPISourceInfo (I believe). >>> >> >> Quack indeed - why does our base error class require so much >> information from a specific part of the generation process? > > Because it's not "a base error class", it's a base error class for the > QAPI schema compiler frontend. > Well. It's the base for every error we /had/. >> Ah, someone changes this in part 4 so that we have a more generic >> error class to use as a base when we are missing such information. > > Evolving it to satisfy a need for a more widely usable error class is > okay. > Yep. It's helpful to keep a very generic form on which we grow other errors from, so that things like the entry point can be written legibly. >> You are witnessing some more future-bleed. >>> Is it really a good idea to do this in generate? It's not about >>> generating code, it's about validating a CLI option. >>> >> >> One might also ask: Is it a good idea to only validate this on a >> frontend, and not in the implementation? > > Yes, because that's where you can emit the better error message more > easily. > > $ python3 scripts/qapi-gen.py --prefix=@ x > scripts/qapi-gen.py: 'funny character '@' in argument of --prefix > > is better than > > $ python3 scripts/qapi-gen.py --prefix=@ x > scripts/qapi-gen.py: funny character '@' in prefix '@' > > In generate(), the knowledge where the offending prefix value comes from > is no longer available. > > To emit this error message, you'd have to raise a sufficiently distinct > error in generate, catch it in main(), then put the error message > together somehow. Bah. > > Aside: there's a stray ' in the old error message. > >> The idea here was to create a function that could be used in a script >> (for tests, debugging interfaces, other python packages) to do all of >> the same things that the CLI tool did, just sans the actual CLI. > > YAGNI. > It's useful for testing and debugging to be able to just call it outside of the CLI, though. Maybe you won't use it, but I will. I could always add the prefix check into a tiny function and give the good error message in main(), and just assert in generate() if you insist on the slightly more specific error message from the CLI script. >> Wouldn't make sense to allow garbage to flow in from one interface but >> not the other; so the check is here. > > "@prefix is sane" is a precondition of generate(). > > When there's a real risk of preconditions getting violated, or readers > getting confused about preconditions, check them with assert. > >>>> + >>>> + 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) >>>> + >>>> + >>>> +def main() -> int: >>>> + """ >>>> + 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") >>> I don't like the changes to default=, because: >>> 1. They are only losely related to the patch's purpose. >>> >> >> Subjective, but OK. >> >>> 2. They split the definition of the CLI: most of it is here, except for >>> defaults, which are defined elsewhere. >>> >> >> All of it is in main.py, though! If you were to, say, move generate() >> elsewhere, it'd look pretty compact as just the CLI frontend, no? > > Same statement is more compact than same screenful is more compact than > same file :) > >>> 3. The defaults will not change, and nothing else uses the constants. >>> >> >> But, fine. Cleber had the same comment but I wasn't fully on-board, >> but two folks saying the same thing ... >> >>>> parser.add_argument('-u', '--unmask-non-abi-names', action='store_true', >>>> dest='unmask', >>>> @@ -32,25 +79,17 @@ 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) >>>> - >>>> - 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) >>>> + print(f"{sys.argv[0]}: {str(err)}", file=sys.stderr) >>>> + return 1 >>>> + return 0 >>> Subtle change: you move the gen_FOO() into the try ... except. >>> Okay; >>> they don't raise QAPIError, but perhaps worth a mention in the commit >>> message. >>> >> >> Forbidden future knowledge; I intend them to. > > I don't mind the move. > >>>> >>>> if __name__ == '__main__': >>>> - main(sys.argv) >>>> + sys.exit(main()) >>> "Python was designed to be easy to understand and fun to use." >>> Ha ha ha. >>> >> >> I mean, I'm having fun, aren't you? > > So many kinds of fun! The fun I'm having with this patch hunk is > mocking "easy and fun" Python for requiring such an elaborate menuett > just to express "can run as program". > > This emperor has no clothes, either. And that's funny, isn't it? >