From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48051) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WmvoF-0004y1-Mk for qemu-devel@nongnu.org; Tue, 20 May 2014 21:59:17 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Wmvo9-00083v-Hp for qemu-devel@nongnu.org; Tue, 20 May 2014 21:59:11 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48247) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wmvo9-00082U-8x for qemu-devel@nongnu.org; Tue, 20 May 2014 21:59:05 -0400 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id s4L1x3Y2030737 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK) for ; Tue, 20 May 2014 21:59:03 -0400 Date: Wed, 21 May 2014 09:59:12 +0800 From: Fam Zheng Message-ID: <20140521015912.GC18886@T430.nay.redhat.com> References: <1400576881-6954-1-git-send-email-famz@redhat.com> <537BA947.9090800@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <537BA947.9090800@redhat.com> Subject: Re: [Qemu-devel] [RFC PATCH v2 0/7] qapi: Specify default value for optional argument in schema json List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake Cc: Kevin Wolf , qemu-devel@nongnu.org, Stefan Hajnoczi On Tue, 05/20 13:13, Eric Blake wrote: > On 05/20/2014 03:07 AM, Fam Zheng wrote: > > Please first take a look at patch 7 to see what is supported by this series. > > > > Patch 1 ~ 3 allows some useful basic types in schema. > > > > Patch 4 ~ 6 implements the new syntax. > > > > Note: The introduced '@arg' sigil, just like the preexisting '*arg', is > > reducing the cleanness of the syntax. We should get rid of both of them in long > > term. Here, this series compromises on this and introduces '@arg' because: > > > > - We have to distinguish the argument property dictionary from nested struct: > > > > I.e.: > > > > 'data': { > > 'arg1': { 'member1': 'int', 'member2': 'str' } > > '@arg2': { 'type': 'int', 'default': 100 } > > } > > > > Until we completely drop and forbid the 'arg1' nested struct use case. > > > > - Forbidding 'arg1' it's doable, but doing it now means we pull in many > > distractive patches to this series. > > Question - since we WANT to get rid of nested struct, why not reverse > the sense? Mark all existing nested structs (weren't there just three > that we found?) with the '@' sigil, and let the new syntax be > sigil-free. Then when we clean up the nesting, we are also getting rid > of the bad syntax, plus the sigil gives us something to search for in > knowing how much to clean up. But if you stick the sigil on the new > code, instead of the obsolete code, then as more and more places in the > schema use defaults, it gets harder and harder to remove the use of the > sigil even if the nested structs are eventually removed. > It makes not much difference I can see. The hard part is actaully dropping nested, converting from sigil <-> non-sigil is easy. Of course, nothing is seriously hard, there are only three nested structs plus some more qapi-schema test code. A question before that is, if we are determined to drop '@' sigil (whether from nested or property dict), are we as determined to drop '*' sigil as well? Fam