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 X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 87F66C433E0 for ; Mon, 18 Jan 2021 18:37:36 +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 D34C422C9E for ; Mon, 18 Jan 2021 18:37:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D34C422C9E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:35812 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l1ZPC-0003xp-PA for qemu-devel@archiver.kernel.org; Mon, 18 Jan 2021 13:37:34 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:33194) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l1ZO3-0003BO-4d for qemu-devel@nongnu.org; Mon, 18 Jan 2021 13:36:23 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:22785) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l1ZO0-0000bn-6P for qemu-devel@nongnu.org; Mon, 18 Jan 2021 13:36:21 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1610994978; 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=cXiPEamr78+vn/BwVAnoagPvSn++LJcggWAuP5mgI0A=; b=dGcRoiW22+4K8g32EKyd5/u5W+VH6gOjOuRca6JkjWAQksvBjlteWLTfGXpvCgb4Y9Gdh8 lm7Ou1KW53woavkNMcI5FydwwUNsn/Y1kV91Z2q719r0m37ODK8lwQcDFA4PLoR6Azstl+ U1Jg/LhRRRfRlNqNuibW1LmFHA+SVos= 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-108-pkSKffTnMMWe7hmpBI16bA-1; Mon, 18 Jan 2021 13:36:14 -0500 X-MC-Unique: pkSKffTnMMWe7hmpBI16bA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id D5FFB59; Mon, 18 Jan 2021 18:36:12 +0000 (UTC) Received: from localhost (ovpn-118-239.rdu2.redhat.com [10.10.118.239]) by smtp.corp.redhat.com (Postfix) with ESMTP id C3D6B5C260; Mon, 18 Jan 2021 18:36:09 +0000 (UTC) Date: Mon, 18 Jan 2021 13:36:08 -0500 From: Eduardo Habkost To: Markus Armbruster Subject: Re: [PATCH v2 06/12] qapi/source: Add builtin null-object sentinel Message-ID: <20210118183608.GB1227584@habkost.net> References: <20201217015927.197287-1-jsnow@redhat.com> <20201217015927.197287-7-jsnow@redhat.com> <878s8wyhgc.fsf@dusky.pond.sub.org> <87eeinab8o.fsf@dusky.pond.sub.org> MIME-Version: 1.0 In-Reply-To: <87eeinab8o.fsf@dusky.pond.sub.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=ehabkost@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Received-SPF: pass client-ip=63.128.21.124; envelope-from=ehabkost@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.175, 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_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 , John Snow , qemu-devel@nongnu.org, =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Cleber Rosa Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Jan 14, 2021 at 02:39:35PM +0100, Markus Armbruster wrote: > John Snow writes: > > > On 1/13/21 10:39 AM, Markus Armbruster wrote: > >> Spelling nitpick: s/builtin/built-in/ in the title. > >> > > > > Sure. > > > >> John Snow writes: > >> > >>> We use None to represent an object that has no source information > >>> because it's a builtin. This complicates interface typing, since many > >>> interfaces expect that there is an info object available to print errors > >>> with. > >>> > >>> Introduce a special QAPISourceInfo that represents these built-ins so > >>> that if an error should so happen to occur relating to one of these > >>> builtins that we will be able to print its information, and interface > >>> typing becomes simpler: you will always have a source info object. > >>> > >>> This object will evaluate as False, so "if info" remains a valid > >>> idiomatic construct. > >>> > >>> NB: It was intentional to not allow empty constructors or similar to > >>> create "empty" source info objects; callers must explicitly invoke > >>> 'builtin()' to pro-actively opt into using the sentinel. This should > >>> prevent use-by-accident. > >>> > >>> Signed-off-by: John Snow > >> > >> As I pointed out in review of v1, this patch has two aspects mixed up: > >> > >> 1. Represent "no source info" as special QAPISourceInfo instead of > >> None > >> > >> 2. On error with "no source info", don't crash. > >> > >> The first one is what de-complicates interface typing. It's clearly > >> serving this patch series' stated purpose: "static typing conversion". > >> > >> The second one is not. It sidetracks us into a design discussion that > >> isn't related to static typing. Maybe it's something we should discuss. > >> Maybe the discussion will make us conclude we want to do this. But > >> letting the static typing work get delayed by that discussion would be > >> stupid, and I'll do what I can to prevent that. > >> > > > > It's not unrelated. It's about finding the most tactical incision to > > make the types as we actually use them correct from a static analysis > > context. > > > > Maybe there's another tactical incision to make that's "smaller", for > > some perception of "smaller", but it's not unrelated. > > We don't have to debate, let alone agree on relatedness. > > >> The stupidest possible solution that preserves the crash is adding an > >> assertion right where it crashes before this patch: in > >> QAPISourceInfo.__str__(). Yes, crashing in a __str__() method is not > >> nice, but it's no worse than before. Making it better than before is a > >> good idea, and you're quite welcome to try, but please not in this > >> series. Add a TODO comment asking for "make it better", then sit on > >> your hands. > > > > I'm recently back from a fairly long PTO, so forgive me if I am > > forgetting something, but I am not really sure I fundamentally > > understand the nature of this critique. > > > > Making functions not "crash" is a side-effect of making the types > > correct. I don't see it as scope-creep, it's a solution to a problem > > under active consideration. > > I disagree. > > The crash you "fix" is *intentional*. I was too lazy to write something > like > > assert self.info > > and instead relied in self.info.whatever to crash. I don't care how it > crashes, as long as it does crash. > > I *like* qapi-gen to crash on such internal errors. It's easy, and > makes "this is a bug, go report it" perfectly clear. > > I'd also be fine with reporting "internal error, this is a bug, go > report it". Not in this series, unless it's utterly trivial, which I > doubt. > > I'm *not* fine with feeding made-up info objects to the user error > reporting machinery without proof that it'll actually produce a useful > error message. Definitely not trivial, thus not in this series. If you really don't want to change the existing behavior of the code, I believe we have only two options: 1) Annotate self.info as QAPISourceInfo (not Optional), and add a hack to make the expression `self.info` crash if the argument to __init__() was None. 2) Annotate self.info as Optional[QAPISourceInfo], and adding manual asserts everywhere self.info is used. Which of those two options do you find acceptable, Markus? -- Eduardo