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=-6.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 BC751C433E0 for ; Thu, 4 Jun 2020 13:51:01 +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 84234207D0 for ; Thu, 4 Jun 2020 13:51:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="geTy5VlK" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 84234207D0 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]:59514 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jgqGq-0004k2-RR for qemu-devel@archiver.kernel.org; Thu, 04 Jun 2020 09:51:00 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:34046) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jgqFk-0003gu-L6 for qemu-devel@nongnu.org; Thu, 04 Jun 2020 09:49:52 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:20626 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jgqFj-0008RX-OW for qemu-devel@nongnu.org; Thu, 04 Jun 2020 09:49:52 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1591278591; 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=e23wmFWVXMxILeHD/g93gx/xA9r5utDrDSmDDipY2uw=; b=geTy5VlKgefrMwa0UGhZgy1TT45u8G75Q8bj3betYdm5I/kensb/n5CdtTBUvmN0pEFPj8 GW7uq/JE1MFQXlIyyrgyIYxXkiCJAKYS94lSWxReEE3h+nZEz9XXhE7FDVqVDo80Aox2zh t/QfU/0s1LEKPTFFnC43InBgaiqfV0Y= 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-193-tODrq4xROO-z7H62DkZdig-1; Thu, 04 Jun 2020 09:49:48 -0400 X-MC-Unique: tODrq4xROO-z7H62DkZdig-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A9302BFC2; Thu, 4 Jun 2020 13:49:47 +0000 (UTC) Received: from linux.fritz.box (ovpn-112-65.ams2.redhat.com [10.36.112.65]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 34B1C7CCC5; Thu, 4 Jun 2020 13:49:46 +0000 (UTC) Date: Thu, 4 Jun 2020 15:49:44 +0200 From: Kevin Wolf To: John Snow Subject: Re: [PATCH v2 05/16] python/qmp.py: add casts to JSON deserialization Message-ID: <20200604134944.GG4512@linux.fritz.box> References: <20200602214528.12107-1-jsnow@redhat.com> <20200602214528.12107-6-jsnow@redhat.com> MIME-Version: 1.0 In-Reply-To: <20200602214528.12107-6-jsnow@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.120; envelope-from=kwolf@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/04 01:14:08 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] 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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN 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: Eduardo Habkost , qemu-block@nongnu.org, qemu-devel@nongnu.org, Max Reitz , Cleber Rosa , philmd@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 02.06.2020 um 23:45 hat John Snow geschrieben: > mypy and python type hints are not powerful enough to properly describe > JSON messages in Python 3.6. The best we can do, generally, is describe > them as Dict[str, Any]. > > Add casts to coerce this type for static analysis; but do NOT enforce > this type at runtime in any way. > > Note: Python 3.8 adds a TypedDict construct which allows for the > description of more arbitrary Dictionary shapes. There is a third-party > module, "Pydantic", which is compatible with 3.6 that can be used > instead of the JSON library that parses JSON messages to fully-typed > Python objects, and may be preferable in some cases. > > (That is well beyond the scope of this commit or series.) > > Signed-off-by: John Snow > --- > python/qemu/qmp.py | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/python/qemu/qmp.py b/python/qemu/qmp.py > index ef3c919b76c..5f3558e3066 100644 > --- a/python/qemu/qmp.py > +++ b/python/qemu/qmp.py > @@ -13,6 +13,7 @@ > import logging > from typing import ( > Any, > + cast, > Dict, > Optional, > TextIO, > @@ -130,7 +131,10 @@ def __json_read(self, only_event=False): > data = self.__sockfile.readline() > if not data: > return None > - resp = json.loads(data) > + # By definition, any JSON received from QMP is a QMPMessage, > + # and we are asserting only at static analysis time that it > + # has a particular shape. > + resp = cast(QMPMessage, json.loads(data)) Instead of casting, you can just specify the variable type: resp: QMPMessage = json.loads(data) I don't think that json.loads() will actually return something other than Any anytime soon, but it's generally nicer to avoid casts and if it eventually does change, we'll get the type check instead of silencing it. > if 'event' in resp: > self.logger.debug("<<< %s", resp) > self.__events.append(resp) > @@ -262,7 +266,7 @@ def command(self, cmd, **kwds): > ret = self.cmd(cmd, kwds) > if 'error' in ret: > raise QMPResponseError(ret) > - return ret['return'] > + return cast(QMPReturnValue, ret['return']) This one can't be easily avoided, though. Kevin