From patchwork Thu May 14 05:53:49 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Snow X-Patchwork-Id: 282781 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 6D549C433E0 for ; Thu, 14 May 2020 06:03:21 +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 3870C205CB for ; Thu, 14 May 2020 06:03:20 +0000 (UTC) Authentication-Results: mail.kernel.org; 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Thu, 14 May 2020 05:54:42 +0000 (UTC) Received: from probe.redhat.com (ovpn-113-9.rdu2.redhat.com [10.10.113.9]) by smtp.corp.redhat.com (Postfix) with ESMTP id 20AF66A977; Thu, 14 May 2020 05:54:41 +0000 (UTC) From: John Snow To: qemu-devel@nongnu.org Subject: [PATCH RFC 18/32] python//qmp.py: add casts to JSON deserialization Date: Thu, 14 May 2020 01:53:49 -0400 Message-Id: <20200514055403.18902-19-jsnow@redhat.com> In-Reply-To: <20200514055403.18902-1-jsnow@redhat.com> References: <20200514055403.18902-1-jsnow@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=205.139.110.61; envelope-from=jsnow@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/13 22:25:42 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] 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_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: Fam Zheng , Kevin Wolf , Vladimir Sementsov-Ogievskiy , Eduardo Habkost , qemu-block@nongnu.org, =?utf-8?q?Alex_Benn?= =?utf-8?b?w6ll?= , Markus Armbruster , Max Reitz , John Snow , Cleber Rosa , =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 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/lib/qmp.py | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/python/qemu/lib/qmp.py b/python/qemu/lib/qmp.py index 0036204218..e460234f2e 100644 --- a/python/qemu/lib/qmp.py +++ b/python/qemu/lib/qmp.py @@ -13,6 +13,7 @@ import logging from typing import ( Any, + cast, Dict, Optional, TextIO, @@ -129,7 +130,10 @@ 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)) if 'event' in resp: self.logger.debug("<<< %s", resp) self.__events.append(resp) @@ -261,7 +265,7 @@ 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']) def pull_event(self, wait=False): """