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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 7E382C636D4 for ; Wed, 15 Feb 2023 11:13:56 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pSFjB-0005NL-OU; Wed, 15 Feb 2023 06:13:33 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pSFj9-0005N8-Ux for qemu-devel@nongnu.org; Wed, 15 Feb 2023 06:13:31 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pSFj8-0004lV-Em for qemu-devel@nongnu.org; Wed, 15 Feb 2023 06:13:31 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1676459609; 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=su8iceknaUOtT76bUSx6KnPGW6mm9i4i4lRlmz53fdI=; b=IYu1uULy7oFNaUwPMn51g9eIll5g/cxe+wEqyvIcxaRv2M9YSB8EtzCuaE8uNnw/kt9O/v 556ZybHmRyE/1hRFI1g/A00oS5bVBSAPkTz7IX0BWSoVFHmtCr9Rs8XWSLkEMM+GFqKiHw jaLxVIeOjp2c3qK3feOnIrd5ZEu604c= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-182-sIAaEU2jON2eBR0c4Q3gBg-1; Wed, 15 Feb 2023 06:13:26 -0500 X-MC-Unique: sIAaEU2jON2eBR0c4Q3gBg-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id C1FB31C07547; Wed, 15 Feb 2023 11:13:25 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.13]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A0E2B140EBF4; Wed, 15 Feb 2023 11:13:25 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 8CABF21E6A1F; Wed, 15 Feb 2023 12:13:24 +0100 (CET) From: Markus Armbruster To: John Snow Cc: qemu-devel@nongnu.org, Michael Roth Subject: Re: [PATCH v4 6/6] qapi: remove JSON value FIXME References: <20230215000011.1725012-1-jsnow@redhat.com> <20230215000011.1725012-7-jsnow@redhat.com> Date: Wed, 15 Feb 2023 12:13:24 +0100 In-Reply-To: <20230215000011.1725012-7-jsnow@redhat.com> (John Snow's message of "Tue, 14 Feb 2023 19:00:11 -0500") Message-ID: <87zg9fb2qz.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 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: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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_NONE=-0.0001, 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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org John Snow writes: > With the two major JSON-ish type hierarchies clarified for distinct > purposes; QAPIExpression for parsed expressions and JSONValue for > introspection data, remove this FIXME as no longer an action item. > > A third JSON-y data type, _ExprValue, is not meant to represent JSON in > the abstract but rather only the possible legal return values from a > single function, get_expr(). It isn't appropriate to attempt to merge it > with either of the above two types. > > In theory, it may be possible to define a completely agnostic > one-size-fits-all JSON type hierarchy that any other user could borrow - > in practice, it's tough to wrangle the differences between invariant, > covariant and contravariant types: input and output parameters demand > different properties of such a structure. > > However, QAPIExpression serves to authoritatively type user input to the > QAPI parser, while JSONValue serves to authoritatively type qapi > generator *output* to be served back to client users at runtime via > QMP. The AST for these two types are different and cannot be wholly > merged into a unified syntax. > > They could, in theory, share some JSON primitive definitions. In > practice, this is currently more trouble than it's worth with mypy's > current expressive power. As such, declare this "done enough for now". > > Signed-off-by: John Snow Reviewed-by: Markus Armbruster