From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9D7F4C4332F for ; Thu, 30 Sep 2021 09:36:12 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0595661278 for ; Thu, 30 Sep 2021 09:36:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 0595661278 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:41924 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mVsU7-0008Nn-0y for qemu-devel@archiver.kernel.org; Thu, 30 Sep 2021 05:36:11 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:34688) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mVsT0-0007cY-Lo for qemu-devel@nongnu.org; Thu, 30 Sep 2021 05:35:03 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:59818) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mVsSx-0002F6-P5 for qemu-devel@nongnu.org; Thu, 30 Sep 2021 05:35:01 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1632994499; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=uyKhSRx/ENyQ3Hd1A3NJxb/wg7jKkxrhI/DlfNmllXM=; b=jEgZTpp0PyzjBm33OlK9ZT+CIqz1GuBQp3Wbtci0qIx2V9YDtWdvG+7ObRlX1E/kES4xK1 lNu+TUdu9j9LjBXWMudlHm2zEJyv5Qa8ln8b0MveHi8eeAl1Py3cTHgSipeBnvmXFZSYS2 JoYMWLTO4U2uVNFgHxjaArGCBFd9bY8= 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-362-ybkjN2T2OmC1-BT01wYHNA-1; Thu, 30 Sep 2021 05:34:57 -0400 X-MC-Unique: ybkjN2T2OmC1-BT01wYHNA-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 14F26100C621; Thu, 30 Sep 2021 09:34:57 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-112-14.ams2.redhat.com [10.36.112.14]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9B591100760B; Thu, 30 Sep 2021 09:34:56 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 2DC60113865F; Thu, 30 Sep 2021 11:34:55 +0200 (CEST) From: Markus Armbruster To: John Snow Subject: Re: [PATCH v3 08/13] qapi/parser: Introduce NullSection References: <20210929194428.1038496-1-jsnow@redhat.com> <20210929194428.1038496-9-jsnow@redhat.com> Date: Thu, 30 Sep 2021 11:34:55 +0200 In-Reply-To: <20210929194428.1038496-9-jsnow@redhat.com> (John Snow's message of "Wed, 29 Sep 2021 15:44:23 -0400") Message-ID: <87tui2qudc.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=armbru@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=170.10.133.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com 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=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-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 , Eric Blake , qemu-devel@nongnu.org, Eduardo Habkost Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" John Snow writes: > Here's the weird bit. QAPIDoc generally expects -- virtually everywhere > -- that it will always have a current section. The sole exception to > this is in the case that end_comment() is called, which leaves us with > *no* section. However, in this case, we also don't expect to actually > ever mutate the comment contents ever again. > > NullSection is just a Null-object that allows us to maintain the > invariant that we *always* have a current section, enforced by static > typing -- allowing us to type that field as QAPIDoc.Section instead of > the more ambiguous Optional[QAPIDoc.Section]. > > end_section is renamed to switch_section and now accepts as an argument > the new section to activate, clarifying that no callers ever just > unilaterally end a section; they only do so when starting a new section. > > Signed-off-by: John Snow > > --- > > For my money: Optional types can be a nuisance because an unfamiliar > reader may wonder in what circumstances the field may be unset. This > makes the condition quite a bit more explicit and statically provable. > > Doing it in this way (and not by creating a dummy section) will also > continue to reject (rather noisily) any erroneous attempts to append > additional lines after end_comment() has been called. > > Also, this section isn't indexed into .sections[] and isn't really > visible in any way to external users of the class, so it seems like a > harmless and low-cost way to formalize the "life cycle" of a QAPIDoc > parser. > > Clean and clear as I can make it, in as few lines as I could muster. > > Signed-off-by: John Snow > --- > scripts/qapi/parser.py | 27 ++++++++++++++++----------- > 1 file changed, 16 insertions(+), 11 deletions(-) > > diff --git a/scripts/qapi/parser.py b/scripts/qapi/parser.py > index 1fdc5bc7056..123fc2f099c 100644 > --- a/scripts/qapi/parser.py > +++ b/scripts/qapi/parser.py > @@ -478,6 +478,13 @@ def __init__(self, parser, name, indent=0): > def connect(self, member): > self.member = member > > + class NullSection(Section): > + """ > + Empty section that signifies the end of a doc block. What about "Dummy section for use at the end of a doc block"? > + """ > + def append(self, line): > + assert False, "BUG: Text appended after end_comment() called." How can a failing assertion *not* be a bug? > + > def __init__(self, parser, info): > # self._parser is used to report errors with QAPIParseError. The > # resulting error position depends on the state of the parser. > @@ -525,7 +532,7 @@ def append(self, line): > self._append_line(line) > > def end_comment(self): > - self._end_section() > + self._switch_section(QAPIDoc.NullSection(self._parser)) > > @staticmethod > def _is_section_tag(name): > @@ -702,9 +709,9 @@ def _start_symbol_section(self, symbols_dict, name, indent): > raise QAPIParseError(self._parser, > "'%s' parameter name duplicated" % name) > assert not self.sections > - self._end_section() > - self._section = QAPIDoc.ArgSection(self._parser, name, indent) > - symbols_dict[name] = self._section > + new_section = QAPIDoc.ArgSection(self._parser, name, indent) > + self._switch_section(new_section) > + symbols_dict[name] = new_section > > def _start_args_section(self, name, indent): > self._start_symbol_section(self.args, name, indent) > @@ -716,13 +723,11 @@ def _start_section(self, name=None, indent=0): > if name in ('Returns', 'Since') and self.has_section(name): > raise QAPIParseError(self._parser, > "duplicated '%s' section" % name) > - self._end_section() > - self._section = QAPIDoc.Section(self._parser, name, indent) > - self.sections.append(self._section) > - > - def _end_section(self): > - assert self._section is not None > + new_section = QAPIDoc.Section(self._parser, name, indent) > + self._switch_section(new_section) > + self.sections.append(new_section) > > + def _switch_section(self, new_section): > text = self._section.text = self._section.text.strip() > > # Only the 'body' section is allowed to have an empty body. > @@ -735,7 +740,7 @@ def _end_section(self): > self._parser, > "empty doc section '%s'" % self._section.name) > > - self._section = None > + self._section = new_section > > def _append_freeform(self, line): > match = re.match(r'(@\S+:)', line) Feels clearer, thanks!