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=-5.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 68349C433ED for ; Fri, 16 Apr 2021 06:05:49 +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 AA9DE6113D for ; Fri, 16 Apr 2021 06:05:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AA9DE6113D 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]:52664 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lXHbv-0006lV-ON for qemu-devel@archiver.kernel.org; Fri, 16 Apr 2021 02:05:47 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:36780) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lXHb9-0006DG-LJ for qemu-devel@nongnu.org; Fri, 16 Apr 2021 02:04:59 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:22426) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lXHb6-0006rb-Fs for qemu-devel@nongnu.org; Fri, 16 Apr 2021 02:04:58 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618553094; 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=iCuETk7+K07XrhLE8Qsg1Jv3m6/uLM9E94e/Ut6mZ2U=; b=UC0j4eNecz5L9RRpNRZWibO9G9IQ3jC8hUfNE+C3gCMqI8x/F9rFKw5lcs11JY5O4dEUaH 9Csl/r/IUtTpe/h0MmolOkiHbFiWj5YC9vvNAAXYF/R/4zyzeWaBOXDoibrHP7gIBch0J0 f58Jr3CMghlirYF6LMbJKMU9vZsrOx4= 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-251-72ydz0BNPDW7HrAyZfyXYQ-1; Fri, 16 Apr 2021 02:04:53 -0400 X-MC-Unique: 72ydz0BNPDW7HrAyZfyXYQ-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 087D81006C82; Fri, 16 Apr 2021 06:04:52 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-114-17.ams2.redhat.com [10.36.114.17]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C0A3360C24; Fri, 16 Apr 2021 06:04:51 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 493BE113525D; Fri, 16 Apr 2021 08:04:50 +0200 (CEST) From: Markus Armbruster To: John Snow Subject: Re: [PATCH v2 1/8] qapi/error: Repurpose QAPIError as a generic exception base class References: <20210330171844.1197918-1-jsnow@redhat.com> <20210330171844.1197918-2-jsnow@redhat.com> <87mtu0gi6u.fsf@dusky.pond.sub.org> <662c4eae-f704-37b4-9d89-f3bbf9108ec2@redhat.com> Date: Fri, 16 Apr 2021 08:04:50 +0200 In-Reply-To: <662c4eae-f704-37b4-9d89-f3bbf9108ec2@redhat.com> (John Snow's message of "Thu, 15 Apr 2021 11:28:33 -0400") Message-ID: <87im4mrchp.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 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=216.205.24.124; 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_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: Peter Maydell , Eduardo Habkost , Michael Roth , Michael Roth , qemu-devel@nongnu.org, Cleber Rosa Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" John Snow writes: > On 4/15/21 2:44 AM, Markus Armbruster wrote: >> John Snow writes: >> >>> Rename QAPIError to QAPISourceError, and then create a new QAPIError >>> class that serves as the basis for all of our other custom exceptions. >> >> Isn't the existing QAPIError such a base class already? Peeking >> ahead... aha, your new base class is abstract. Can you explain why we >> that's useful? >> > > Sure. The existing QAPIError class assumes that it's an error that has a > source location, but not all errors will. The idea is that an abstract > error class can be used as the ancestor for all other errors in a > type-safe way, such that: > > try: > qapi.something_or_other() > except QAPIError as err: > err.some_sort_of_method() > > (1) This is a type-safe construct, and > (2) This is sufficient to catch all errors that originate from within > the library, regardless of their exact type. > > Primarily, it's a ploy to get the SourceInfo stuff out of the > common/root exception for type safety reasons. > > (Later in the series, you'll see there's a few places where we try to > fake SourceInfo stuff in order to use QAPIError, by shuffling this > around, we allow ourselves to raise exceptions that don't need this > hackery.) I think you're conflating a real issue with a non-issue. The real issue: you want to get rid of fake QAPISourceInfo. This isn't terribly important, but small cleanups count, too. I can't see the "few places where we try to fake" in this series, though. Is it in a later part, or am I just blind? The non-issue: wanting a common base class. Yes, we want one, but we already got one: QAPIError. I think the commit message should explain the real issue more clearly, without confusing readers with the non-issue. Makes sense?