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bh=UgvrgSwEqqZCXHYY5MeRc1qWTpzeHbpjC8zyLBwUa30=; b=WcPcFGy7Q1jA+snl0SojLfHuwyNJWYOEWj3Idv4FiAQbW0+YiSvHa5drMMBr4XdMFzrdid xYkJU7KikXQsickvylBgF+GhilLdt3baiJNaymc9el5QnwvBMGjaym0y2SNvPwRf2WWujG ItV6GpOkimBsuNy5DiXEeFXxX7any84= 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-544-JemRtkmtMhO7ivRQxS-Sqg-1; Wed, 05 May 2021 15:09:13 -0400 X-MC-Unique: JemRtkmtMhO7ivRQxS-Sqg-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5A2AD10066E5; Wed, 5 May 2021 19:09:12 +0000 (UTC) Received: from [10.10.117.64] (ovpn-117-64.rdu2.redhat.com [10.10.117.64]) by smtp.corp.redhat.com (Postfix) with ESMTP id A863260C17; Wed, 5 May 2021 19:09:09 +0000 (UTC) Subject: Re: [PATCH 11/22] qapi/parser: Rework _check_pragma_list_of_str as a TypeGuard To: Markus Armbruster References: <20210422030720.3685766-1-jsnow@redhat.com> <20210422030720.3685766-12-jsnow@redhat.com> <871ray7dfd.fsf@dusky.pond.sub.org> <83aa318c-1a54-35a2-2cec-8d4503392c2f@redhat.com> <87czug6vw5.fsf@dusky.pond.sub.org> From: John Snow Message-ID: <5d035f43-ddd5-f0bf-b2b3-08075b3bdd76@redhat.com> Date: Wed, 5 May 2021 15:09:08 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <87czug6vw5.fsf@dusky.pond.sub.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 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: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=jsnow@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.693, 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_LOW=-0.7, 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: Michael Roth , Cleber Rosa , qemu-devel@nongnu.org, Eduardo Habkost Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 4/27/21 3:15 AM, Markus Armbruster wrote: > John Snow writes: > >> On 4/25/21 8:32 AM, Markus Armbruster wrote: >>> John Snow writes: >>> >>>> TypeGuards wont exist in Python proper until 3.10. Ah well. We can hack >>>> up our own by declaring this function to return the type we claim it >>>> checks for and using this to safely downcast object -> List[str]. >>>> >>>> In so doing, I bring this function in-line under _pragma so it can use >>>> the 'info' object in its closure. Having done this, _pragma also now >>>> no longer needs to take a 'self' parameter, so drop it. >>>> >>>> Rename it to just _check(), to help us out with the line-length -- and >>>> now that it's contained within _pragma, it is contextually easier to see >>>> how it's used anyway -- especially with types. >>>> >>>> Signed-off-by: John Snow >>>> >>>> --- >>>> >>>> I left (name, value) as args to avoid creating a fully magic "macro", >>>> though, I thought this was too weird: >>>> >>>> info.pragma.foobar = _check() >>>> >>>> and it looked more reasonable as: >>>> >>>> info.pragma.foobar = _check(name, value) >>>> >>>> Signed-off-by: John Snow >>>> --- >>>> scripts/qapi/parser.py | 26 +++++++++++++------------- >>>> 1 file changed, 13 insertions(+), 13 deletions(-) >>>> >>>> diff --git a/scripts/qapi/parser.py b/scripts/qapi/parser.py >>>> index 16fd36f8391..d02a134aae9 100644 >>>> --- a/scripts/qapi/parser.py >>>> +++ b/scripts/qapi/parser.py >>>> @@ -17,6 +17,7 @@ >>>> from collections import OrderedDict >>>> import os >>>> import re >>>> +from typing import List >>>> >>>> from .common import match_nofail >>>> from .error import QAPISemError, QAPISourceError >>>> @@ -151,28 +152,27 @@ def _include(include, info, incl_fname, previously_included): >>>> ) from err >>>> >>>> @staticmethod >>>> - def _check_pragma_list_of_str(name, value, info): >>>> - if (not isinstance(value, list) >>>> - or any([not isinstance(elt, str) for elt in value])): >>>> - raise QAPISemError( >>>> - info, >>>> - "pragma %s must be a list of strings" % name) >>>> + def _pragma(name, value, info): >>>> + >>>> + def _check(name, value) -> List[str]: >>>> + if (not isinstance(value, list) or >>>> + any([not isinstance(elt, str) for elt in value])): >>>> + raise QAPISemError( >>>> + info, >>>> + "pragma %s must be a list of strings" % name) >>>> + return value >>>> >>>> - def _pragma(self, name, value, info): >>>> if name == 'doc-required': >>>> if not isinstance(value, bool): >>>> raise QAPISemError(info, >>>> "pragma 'doc-required' must be boolean") >>>> info.pragma.doc_required = value >>>> elif name == 'command-name-exceptions': >>>> - self._check_pragma_list_of_str(name, value, info) >>>> - info.pragma.command_name_exceptions = value >>>> + info.pragma.command_name_exceptions = _check(name, value) >>>> elif name == 'command-returns-exceptions': >>>> - self._check_pragma_list_of_str(name, value, info) >>>> - info.pragma.command_returns_exceptions = value >>>> + info.pragma.command_returns_exceptions = _check(name, value) >>>> elif name == 'member-name-exceptions': >>>> - self._check_pragma_list_of_str(name, value, info) >>>> - info.pragma.member_name_exceptions = value >>>> + info.pragma.member_name_exceptions = _check(name, value) >>>> else: >>>> raise QAPISemError(info, "unknown pragma '%s'" % name) >>> >>> While I appreciate the terseness, I'm not sure I like the generic name >>> _check() for checking one of two special cases, namely "list of string". >>> The other case being "boolean". We could acquire more cases later. >>> >> >> Yeah, sorry, just trying to make the line fit ... > > I understand! > >> The important thing is that we need to make sure this routine returns >> some known type. It's just that the block down here has very long lines. >> >> Recommendations? > > Moving the helper into _pragma() lets us drop shorten its name. Still > too long to fit the line: > > info.pragma.command_returns_exceptions = check_list_str(name, value) > > We could break the line in the argument list: > > info.pragma.command_returns_exceptions = check_list_str(name, > value) > > or > > info.pragma.command_returns_exceptions = check_list_str( > name, value) > > Not exactly pretty. > > We could shorten the assignment's target: > > pragma.command_returns_exceptions = check_list_str(name, value) > > with > > pragma.info = pragma > 🙃 > before the conditional. I'm not too fond of creating aliases, but this > one looks decent to me. What do you think? > If it works for you, it works for me! --js