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 C4318C4706C for ; Tue, 16 Jan 2024 11:10:46 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rPhKE-0003v2-V5; Tue, 16 Jan 2024 06:09:46 -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 1rPhKD-0003tb-IA for qemu-devel@nongnu.org; Tue, 16 Jan 2024 06:09:45 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rPhK9-0002JX-6k for qemu-devel@nongnu.org; Tue, 16 Jan 2024 06:09:45 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1705403379; 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=1+2eEVMjcbnVY+WResrPUA93mbwnyhJHe09kzTkKi6g=; b=AW8g/B1IGqpex9GIz/DQd8Uwi3wYVhee8sleM86WiZNkUt3+sPjpc+vCn+Lmx6rxKSi6xx V9/D0zgSldTxBzibAq07tugvGgwvWL6InQ5gZ8/oHvDCj9+lSiw/ssWLq3YyjlsIpN16xA MjNBUH3qBqIuwQc5l5fdAh1Ts/o+jLE= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-623-ZsMYprfqOc-zcnZhhnudMQ-1; Tue, 16 Jan 2024 06:09:36 -0500 X-MC-Unique: ZsMYprfqOc-zcnZhhnudMQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 1AD9486EB22; Tue, 16 Jan 2024 11:09:36 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.128]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B920028AC; Tue, 16 Jan 2024 11:09:35 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 8688621E680D; Tue, 16 Jan 2024 12:09:33 +0100 (CET) From: Markus Armbruster To: John Snow Cc: qemu-devel@nongnu.org, Michael Roth , Peter Maydell Subject: Re: [PATCH v2 09/19] qapi/schema: allow resolve_type to be used for built-in types In-Reply-To: <20240112222945.3033854-10-jsnow@redhat.com> (John Snow's message of "Fri, 12 Jan 2024 17:29:35 -0500") References: <20240112222945.3033854-1-jsnow@redhat.com> <20240112222945.3033854-10-jsnow@redhat.com> Date: Tue, 16 Jan 2024 12:09:33 +0100 Message-ID: <87cyu15yc2.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.5 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.531, 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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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: > allow resolve_type to be used for both built-in and user-specified > type definitions. In the event that the type cannot be resolved, assert > that 'info' and 'what' were both provided in order to create a usable > QAPISemError. > > In practice, 'info' will only be None for built-in definitions, which > *should not fail* type lookup. > > As a convenience, allow the 'what' and 'info' parameters to be elided > entirely so that it can be used as a can-not-fail version of > lookup_type. The convenience remains unused until the next patch. It should be added there. > Note: there are only three callsites to resolve_type at present where > "info" is perceived to be possibly None: > > 1) QAPISchemaArrayType.check() > 2) QAPISchemaObjectTypeMember.check() > 3) QAPISchemaEvent.check() > > Of those three, only the first actually ever passes None; Yes. More below. > the other two > are limited by their base class initializers which accept info=None, but They do? > neither actually use it in practice. > > Signed-off-by: John Snow Hmm. We look up types by name in two ways: 1. Failure is a semantic error Use .resolve_type(), passing real @info and @what. Users: * QAPISchemaArrayType.check() resolving the element type Fine print: when the array type is built-in, we pass None @info and @what. The built-in array type's element type must exist for .resolve_type() to work. This commit changes .resolve_type() to assert it does. * QAPISchemaObjectType.check() resolving the base type * QAPISchemaObjectTypeMember.check() resolving the member type * QAPISchemaCommand.check() resolving argument type (if named) and return type (which is always named). * QAPISchemaEvent.check() resolving argument type (if named). Note all users are in .check() methods. That's where type named get resolved. 2. Handle failure Use .lookup_type(), which returns None when the named type doesn't exist. Users: * QAPISchemaVariants.check(), to look up the base type containing the tag member for error reporting purposes. Failure would be a programming error. * .resolve_type(), which handles failure as semantic error * ._make_array_type(), which uses it as "type exists already" predicate. * QAPISchemaGenIntrospectVisitor._use_type(), to look up certain built-in types. Failure would be a programming error. The next commit switches the uses where failure would be a programming error from .lookup_type() to .resolve_type() without @info and @what, so failure trips its assertion. I don't like it, because it overloads .resolve_type() to serve two rather different use cases: 1. Failure is a semantic error; pass @info and @what 2. Failure is a programming error; don't pass @info and what The odd one out is of course QAPISchemaArrayType.check(), which wants to use 1. for the user's types and 2. for built-in types. Let's ignore it for a second. I prefer to do 2. like typ = .lookup_type(); assert typ. We can factor this out into its own helper if that helps (pardon the pun). Back to QAPISchemaArrayType.check(). Its need to resolve built-in element types, which have no info, necessitates .resolve_type() taking Optional[QAPISourceInfo]. This might bother you. It doesn't bother me, unless it leads to mypy complications I can't see. We can simply leave it as is. Adding the assertion to .resolve_type() is fine. Ot we complicate QAPISchemaArrayType.check() to simplify .resolve_type()'s typing, roughly like this: if self.info: self.element_type = schema.resolve_type( self._element_type_name, self.info, self.info.defn_meta) else: # built-in type self.element_type = schema.lookup_type( self._element_type_name) assert self.element_type Not sure it's worth the trouble. Thoughts? > --- > scripts/qapi/schema.py | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py > index 66a78f28fd4..a77b51d1b96 100644 > --- a/scripts/qapi/schema.py > +++ b/scripts/qapi/schema.py > @@ -1001,9 +1001,10 @@ def lookup_type(self, name): > assert typ is None or isinstance(typ, QAPISchemaType) > return typ > > - def resolve_type(self, name, info, what): > + def resolve_type(self, name, info=None, what=None): > typ = self.lookup_type(name) > if not typ: > + assert info and what # built-in types must not fail lookup > if callable(what): > what = what(info) > raise QAPISemError(