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Wed, 18 Nov 2020 16:41:16 +0100 (CET) From: Markus Armbruster To: John Snow Subject: Re: [PATCH v2 07/16] qapi/expr.py: Add casts in a few select cases References: <20201026213637.47087-1-jsnow@redhat.com> <20201026213637.47087-8-jsnow@redhat.com> Date: Wed, 18 Nov 2020 16:41:16 +0100 In-Reply-To: <20201026213637.47087-8-jsnow@redhat.com> (John Snow's message of "Mon, 26 Oct 2020 17:36:28 -0400") Message-ID: <873616isf7.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=armbru@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=216.205.24.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/11/18 00:38:29 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_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: Cleber Rosa , qemu-devel@nongnu.org, Eduardo Habkost Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 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 2654a72e8333..b8720b723377 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 Suggest # check_exprs() ensures this > members = expr['data'] > > 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 Likewise. > base = expr.get('base') > discriminator = expr.get('discriminator') > members = expr['data'] > @@ -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: > check_name_is_str(name, info, "'%s'" % meta) Uh, why do we need to cast then? It's not actually "asserted". check_name_is_str() ensures str by raising an error if not str. > info.set_defn(meta, name) > check_defn_name_str(name, info, meta)