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=-15.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 D7B97C433DB for ; Wed, 24 Feb 2021 22:26:07 +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 20F3D64E05 for ; Wed, 24 Feb 2021 22:26:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 20F3D64E05 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]:36354 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lF2be-0003Vn-1o for qemu-devel@archiver.kernel.org; Wed, 24 Feb 2021 17:26:06 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:35902) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lF2aK-0002yo-W7 for qemu-devel@nongnu.org; Wed, 24 Feb 2021 17:24:45 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:45956) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1lF2aH-0004Hk-Ne for qemu-devel@nongnu.org; Wed, 24 Feb 2021 17:24:44 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1614205476; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=hivRdI2B8yYXyCTS/Dtz2ijLrXqfBd9iPZw+NvYXeGs=; b=YxLH2D6iKVq0Q1Rg0XOPqve1nTbvOUhL8WhIvpDjz/TlSogn/pq35FfRezrM4XyIlGCYG4 gEnAqSKMW8JjueH8ZYaWlvvZzf58G+fn7h7mnSn/5L60RKx7QdQT3NUiv7ntuZs5cg+sMz HsN8STBSP6HbJSHr8H5UxjW/2Fr2JOE= 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-195-tKmeHHLkMAqnOI1cosYP5w-1; Wed, 24 Feb 2021 17:24:33 -0500 X-MC-Unique: tKmeHHLkMAqnOI1cosYP5w-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 260EE18C35BD; Wed, 24 Feb 2021 22:24:32 +0000 (UTC) Received: from [10.10.112.247] (ovpn-112-247.rdu2.redhat.com [10.10.112.247]) by smtp.corp.redhat.com (Postfix) with ESMTP id 79E3860BE5; Wed, 24 Feb 2021 22:24:31 +0000 (UTC) Subject: Re: [PATCH v3 07/16] qapi/expr.py: Add casts in a few select cases To: Markus Armbruster References: <20210223003408.964543-1-jsnow@redhat.com> <20210223003408.964543-8-jsnow@redhat.com> <87zgzt1w9w.fsf@dusky.pond.sub.org> From: John Snow Message-ID: <9b9b1b1d-1988-2bbd-4f6e-6374ebd3cd88@redhat.com> Date: Wed, 24 Feb 2021 17:24:31 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <87zgzt1w9w.fsf@dusky.pond.sub.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jsnow@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=jsnow@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, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=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: Michael Roth , Cleber Rosa , qemu-devel@nongnu.org, Eduardo Habkost Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2/24/21 7:32 AM, Markus Armbruster wrote: > John Snow writes: > >> Casts are instructions to the type checker only, they aren't "safe" and >> should probably be avoided in general. In this case, when we perform >> type checking on a nested structure, the type of each field does not >> "stick". >> >> We don't need to assert that something is a str if we've already checked >> that it is -- use a cast instead for these cases. >> >> Signed-off-by: John Snow >> Reviewed-by: Eduardo Habkost >> Reviewed-by: Cleber Rosa >> --- >> scripts/qapi/expr.py | 8 ++++---- >> 1 file changed, 4 insertions(+), 4 deletions(-) >> >> diff --git a/scripts/qapi/expr.py b/scripts/qapi/expr.py >> index afa6bd07769..f45d6be1f4c 100644 >> --- a/scripts/qapi/expr.py >> +++ b/scripts/qapi/expr.py >> @@ -15,7 +15,7 @@ >> # See the COPYING file in the top-level directory. >> >> import re >> -from typing import MutableMapping, Optional >> +from typing import MutableMapping, Optional, cast >> >> from .common import c_name >> from .error import QAPISemError >> @@ -232,7 +232,7 @@ def check_enum(expr, info): >> >> >> def check_struct(expr, info): >> - name = expr['struct'] >> + name = cast(str, expr['struct']) # Asserted in check_exprs >> members = expr['data'] >> > > I believe you need this only so you can declare check_type()'s > allow_dict to be Optional[str]. More busy-work around allow_dict... > > I'm tempted to ask for allow_dict: Any and call it a day. > You're right, this is because of the signature for the allow_dict argument. Ultimately, the pragma is a collection of strings and we need to prove we are looking up a string somewhere or other. (Or tell the type checker to leave us alone.) Unfortunately, the "check" in check_exprs falls off almost immediately. Working with dictly-typed objects is a little annoying for this reason. This works for now; but finding a better way to do the pragma checks is probably the more correct thing. (And not something I really want to try and get through review until we're done typing, I think.) >> check_type(members, info, "'data'", allow_dict=name) >> @@ -240,7 +240,7 @@ def check_struct(expr, info): >> >> >> def check_union(expr, info): >> - name = expr['union'] >> + name = cast(str, expr['union']) # Asserted in check_exprs >> base = expr.get('base') >> discriminator = expr.get('discriminator') >> members = expr['data'] > > Likwewise. > >> @@ -337,7 +337,7 @@ def check_exprs(exprs): >> else: >> raise QAPISemError(info, "expression is missing metatype") >> >> - name = expr[meta] >> + name = cast(str, expr[meta]) # Asserted right below: > > "Checked", not "asserted". > Oh, yes. >> check_name_is_str(name, info, "'%s'" % meta) >> info.set_defn(meta, name) >> check_defn_name_str(name, info, meta) > > > Cast before check gives me a queasy feeling. It's lying to the type > checker. > > Hamfisted way to avoid lying: > > check_name_is_str(expr[meta], ...) > name = cast(str, expr[meta]) > > Something like > > name = check_name_is_str(name, ...) > > might be neater, but then we'd have to find a better function name. > OK, I'll look into re-ordering this.