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spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:47234 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lX3w1-0000iu-1n for qemu-devel@archiver.kernel.org; Thu, 15 Apr 2021 11:29:37 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:52588) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lX3vA-00006I-NY for qemu-devel@nongnu.org; Thu, 15 Apr 2021 11:28:44 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:22608) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lX3v8-0002PN-F1 for qemu-devel@nongnu.org; Thu, 15 Apr 2021 11:28:44 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618500521; 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=ylSQA9EkPa2i8acTMLEJ7IeA3v2ef/TIjU6kvAiY5js=; b=f/YPvcgeyg8Ut00f3qLI5j2JE2CL17nZ1IrAco3wnWNrIJ7chCAevPrwBwLAr/lwF+H+Be kSh5L++46pFd0a2k2qpPdlxdMsqkzaNw1UmRLr74v5YXUv8zkNgCUdePpEBc85FS+/8Qk7 z2bulzb8zLRzk9IpN8w/Ifbv2nyP+rg= 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-279-WV-iiReUMuGweXQhzBSCEA-1; Thu, 15 Apr 2021 11:28:36 -0400 X-MC-Unique: WV-iiReUMuGweXQhzBSCEA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DC6268030D0; Thu, 15 Apr 2021 15:28:34 +0000 (UTC) Received: from [10.10.117.61] (ovpn-117-61.rdu2.redhat.com [10.10.117.61]) by smtp.corp.redhat.com (Postfix) with ESMTP id E36D55C3E4; Thu, 15 Apr 2021 15:28:33 +0000 (UTC) Subject: Re: [PATCH v2 1/8] qapi/error: Repurpose QAPIError as a generic exception base class To: Markus Armbruster References: <20210330171844.1197918-1-jsnow@redhat.com> <20210330171844.1197918-2-jsnow@redhat.com> <87mtu0gi6u.fsf@dusky.pond.sub.org> From: John Snow Message-ID: <662c4eae-f704-37b4-9d89-f3bbf9108ec2@redhat.com> Date: Thu, 15 Apr 2021 11:28:33 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <87mtu0gi6u.fsf@dusky.pond.sub.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 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_H4=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: Peter Maydell , Eduardo Habkost , Michael Roth , Michael Roth , qemu-devel@nongnu.org, Cleber Rosa Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 4/15/21 2:44 AM, Markus Armbruster wrote: > John Snow writes: > >> Rename QAPIError to QAPISourceError, and then create a new QAPIError >> class that serves as the basis for all of our other custom exceptions. > > Isn't the existing QAPIError such a base class already? Peeking > ahead... aha, your new base class is abstract. Can you explain why we > that's useful? > Sure. The existing QAPIError class assumes that it's an error that has a source location, but not all errors will. The idea is that an abstract error class can be used as the ancestor for all other errors in a type-safe way, such that: try: qapi.something_or_other() except QAPIError as err: err.some_sort_of_method() (1) This is a type-safe construct, and (2) This is sufficient to catch all errors that originate from within the library, regardless of their exact type. Primarily, it's a ploy to get the SourceInfo stuff out of the common/root exception for type safety reasons. (Later in the series, you'll see there's a few places where we try to fake SourceInfo stuff in order to use QAPIError, by shuffling this around, we allow ourselves to raise exceptions that don't need this hackery.) >> Add docstrings to explain the intended function of each error class. >> >> Signed-off-by: John Snow >> --- >> docs/sphinx/qapidoc.py | 3 ++- >> scripts/qapi/error.py | 11 +++++++++-- >> scripts/qapi/schema.py | 5 +++-- >> 3 files changed, 14 insertions(+), 5 deletions(-) >> >> diff --git a/docs/sphinx/qapidoc.py b/docs/sphinx/qapidoc.py >> index b7b86b5dff..458b1f477e 100644 >> --- a/docs/sphinx/qapidoc.py >> +++ b/docs/sphinx/qapidoc.py >> @@ -34,7 +34,8 @@ >> from sphinx.util.nodes import nested_parse_with_titles >> import sphinx >> from qapi.gen import QAPISchemaVisitor >> -from qapi.schema import QAPIError, QAPISemError, QAPISchema >> +from qapi.error import QAPIError, QAPISemError >> +from qapi.schema import QAPISchema >> >> >> # Sphinx up to 1.6 uses AutodocReporter; 1.7 and later >> diff --git a/scripts/qapi/error.py b/scripts/qapi/error.py >> index ae60d9e2fe..126dda7c9b 100644 >> --- a/scripts/qapi/error.py >> +++ b/scripts/qapi/error.py >> @@ -13,6 +13,11 @@ >> >> >> class QAPIError(Exception): >> + """Base class for all exceptions from the QAPI package.""" >> + >> + >> +class QAPISourceError(QAPIError): >> + """Error class for all exceptions identifying a source location.""" >> def __init__(self, info, col, msg): >> Exception.__init__(self) >> self.info = info >> @@ -27,7 +32,8 @@ def __str__(self): >> return loc + ': ' + self.msg >> >> >> -class QAPIParseError(QAPIError): >> +class QAPIParseError(QAPISourceError): >> + """Error class for all QAPI schema parsing errors.""" >> def __init__(self, parser, msg): >> col = 1 >> for ch in parser.src[parser.line_pos:parser.pos]: >> @@ -38,6 +44,7 @@ def __init__(self, parser, msg): >> super().__init__(parser.info, col, msg) >> >> >> -class QAPISemError(QAPIError): >> +class QAPISemError(QAPISourceError): >> + """Error class for semantic QAPI errors.""" >> def __init__(self, info, msg): >> super().__init__(info, None, msg) >> diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py >> index 01cdd753cd..1849c3e45f 100644 >> --- a/scripts/qapi/schema.py >> +++ b/scripts/qapi/schema.py >> @@ -20,7 +20,7 @@ >> from typing import Optional >> >> from .common import POINTER_SUFFIX, c_name >> -from .error import QAPIError, QAPISemError >> +from .error import QAPISemError, QAPISourceError >> from .expr import check_exprs >> from .parser import QAPISchemaParser >> >> @@ -878,7 +878,8 @@ def _def_entity(self, ent): >> other_ent = self._entity_dict.get(ent.name) >> if other_ent: >> if other_ent.info: >> - where = QAPIError(other_ent.info, None, "previous definition") >> + where = QAPISourceError(other_ent.info, None, >> + "previous definition") >> raise QAPISemError( >> ent.info, >> "'%s' is already defined\n%s" % (ent.name, where))