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=-0.8 required=3.0 tests=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 C3427C04EBF for ; Mon, 23 Sep 2019 11:46:42 +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 95EE6207FD for ; Mon, 23 Sep 2019 11:46:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 95EE6207FD 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]:55100 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iCMnh-0004Wa-KV for qemu-devel@archiver.kernel.org; Mon, 23 Sep 2019 07:46:41 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:43662) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iCMm0-0003e9-P2 for qemu-devel@nongnu.org; Mon, 23 Sep 2019 07:44:58 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iCMlz-0004KK-FU for qemu-devel@nongnu.org; Mon, 23 Sep 2019 07:44:56 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45928) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iCMlz-0004HU-9d for qemu-devel@nongnu.org; Mon, 23 Sep 2019 07:44:55 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 90C213082145; Mon, 23 Sep 2019 11:44:53 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-117-142.ams2.redhat.com [10.36.117.142]) by smtp.corp.redhat.com (Postfix) with ESMTPS id EC7FF5D717; Mon, 23 Sep 2019 11:44:50 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 74CEC113864E; Mon, 23 Sep 2019 13:44:49 +0200 (CEST) From: Markus Armbruster To: Eric Blake Subject: Re: [Qemu-devel] [PATCH v2 13/16] docs/devel/qapi-code-gen: Rewrite compatibility considerations References: <20190910063724.28470-1-armbru@redhat.com> <20190910063724.28470-14-armbru@redhat.com> <60b61f7c-fe08-e78b-dd52-775959af99d9@redhat.com> <87tv9g8cf4.fsf@dusky.pond.sub.org> Date: Mon, 23 Sep 2019 13:44:49 +0200 In-Reply-To: (Eric Blake's message of "Tue, 17 Sep 2019 11:11:48 -0500") Message-ID: <87impjp77y.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.42]); Mon, 23 Sep 2019 11:44:53 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 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: marcandre.lureau@redhat.com, qemu-devel@nongnu.org, mdroth@linux.vnet.ibm.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Eric Blake writes: > On 9/13/19 10:05 AM, Markus Armbruster wrote: > >>>> +Any change to a command definition's 'data' or one of the types used >>>> +there (recursively) needs to consider send direction compatibility. >>>> + >>>> +Any change to a command definition's 'return', an event definition's >>>> +'data', or one of the types used there (recursively) needs to consider >>>> +receive direction compatibility. >>>> + >>>> +Any change to types used in both contexts need to consider both. >>>> + >>>> +Members of enumeration types, complex types and alternate types may be >>>> +reordered freely. For enumerations and alternate types, this doesn't >>>> +affect the wire encoding. For complex types, this might make the >>>> +implementation emit JSON object members in a different order, which >>>> +the Client JSON Protocol permits. >>> >>> Worth mentioning that type names themselves are NOT part of the >>> interface, and may be freely renamed? >> >> Care to suggest a suitable sentence? > > Although member names within a type cannot be changed without affecting > compatibility, This part seems redundant with the previous paragraph. > changes to type names themselves do not affect the > protocol. As such, complex types may be freely renamed or refactored, All types (enums, structs, simple & flat unions, alternates) actually, not just complex ones (structs, unions). > such as splitting members from one type into a common base type, as long > as the resulting set of members remain compatible. What does it mean for a set of members to be compatible? We don't actually define that... What about: Since type names are not visible in the Client JSON Protocol, types may be freely renamed. Even certain refactorings are invisible, such as splitting members from one type into a common base type.