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Thu, 14 Mar 2024 06:59:24 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHFt1w97Tpo7uxFEh3fceur9h/58wmCJN/BZqHIDw93dJMcrapgoWjCbhEh1vsE2bCXAtTvl722yjn0XyY241Y= X-Received: by 2002:a17:90b:148d:b0:29b:9daa:3a92 with SMTP id js13-20020a17090b148d00b0029b9daa3a92mr23760pjb.31.1710424764521; Thu, 14 Mar 2024 06:59:24 -0700 (PDT) MIME-Version: 1.0 References: <20240313044127.49089-1-jsnow@redhat.com> <20240313044127.49089-17-jsnow@redhat.com> <87a5n19dce.fsf@pond.sub.org> <87msr09aq6.fsf@pond.sub.org> In-Reply-To: <87msr09aq6.fsf@pond.sub.org> From: John Snow Date: Thu, 14 Mar 2024 09:59:12 -0400 Message-ID: Subject: Re: [PATCH v4 16/23] qapi/schema: Don't initialize "members" with `None` To: Markus Armbruster Cc: qemu-devel , Peter Maydell , Michael Roth Content-Type: multipart/alternative; boundary="000000000000813b3d06139f4ca7" Received-SPF: pass client-ip=170.10.129.124; envelope-from=jsnow@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.987, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, T_SCC_BODY_TEXT_LINE=-0.01, T_SPF_TEMPERROR=0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org --000000000000813b3d06139f4ca7 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, Mar 14, 2024, 9:58=E2=80=AFAM Markus Armbruster = wrote: > John Snow writes: > > > On Thu, Mar 14, 2024, 9:01=E2=80=AFAM Markus Armbruster > wrote: > > > >> John Snow writes: > >> > >> > Declare, but don't initialize the "members" field with type > >> > List[QAPISchemaObjectTypeMember]. > >> > > >> > This simplifies the typing from what would otherwise be > >> > Optional[List[T]] to merely List[T]. This removes the need to add > >> > assertions to several callsites that this value is not None - which = it > >> > never will be after the delayed initialization in check() anyway. > >> > > >> > The type declaration without initialization trick will cause > accidental > >> > uses of this field prior to full initialization to raise an > >> > AttributeError. > >> > > >> > (Note that it is valid to have an empty members list, see the intern= al > >> > q_empty object as an example. For this reason, we cannot use the emp= ty > >> > list as a replacement test for full initialization and instead rely = on > >> > the _checked/_check_complete fields.) > >> > > >> > Signed-off-by: John Snow > >> > --- > >> > scripts/qapi/schema.py | 12 +++++++----- > >> > 1 file changed, 7 insertions(+), 5 deletions(-) > >> > > >> > diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py > >> > index 50ebc4f12de..fb30314741a 100644 > >> > --- a/scripts/qapi/schema.py > >> > +++ b/scripts/qapi/schema.py > >> > @@ -20,7 +20,7 @@ > >> > from collections import OrderedDict > >> > import os > >> > import re > >> > -from typing import List, Optional > >> > +from typing import List, Optional, cast > >> > > >> > from .common import ( > >> > POINTER_SUFFIX, > >> > @@ -449,7 +449,7 @@ def __init__(self, name, info, doc, ifcond, > features, > >> > self.base =3D None > >> > self.local_members =3D local_members > >> > self.variants =3D variants > >> > - self.members =3D None > >> > + self.members: List[QAPISchemaObjectTypeMember] > >> > self._check_complete =3D False > >> > > >> > def check(self, schema): > >> > @@ -482,7 +482,11 @@ def check(self, schema): > >> > for m in self.local_members: > >> > m.check(schema) > >> > m.check_clash(self.info, seen) > >> > - members =3D seen.values() > >> > + > >> > + # check_clash works in terms of the supertype, but > local_members > >> > + # is asserted to be List[QAPISchemaObjectTypeMember]. > >> > >> Do you mean "but self.members is declared as > >> List[QAPISchemaObjectTypeMember]"? > > > > Argh. I meant asserted in the linguistic sense. mypy asserts it to be; > not > > a runtime assertion. > > > > I do this a lot, apparently. > > Okay to adjust your comment to my version? > Absolutely, of course! > [...] > > --000000000000813b3d06139f4ca7 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


On Thu, Mar 14, 2024, 9:58=E2=80=AFAM Markus Armbruste= r <armbru@redhat.com> wrote:=
John Snow <jsnow@redhat.com&g= t; writes:

> On Thu, Mar 14, 2024, 9:01=E2=80=AFAM Markus Armbruster <armbru@redh= at.com> wrote:
>
>> John Snow <jsnow@redhat.com> writes:
>>
>> > Declare, but don't initialize the "members" fie= ld with type
>> > List[QAPISchemaObjectTypeMember].
>> >
>> > This simplifies the typing from what would otherwise be
>> > Optional[List[T]] to merely List[T]. This removes the need to= add
>> > assertions to several callsites that this value is not None -= which it
>> > never will be after the delayed initialization in check() any= way.
>> >
>> > The type declaration without initialization trick will cause = accidental
>> > uses of this field prior to full initialization to raise an >> > AttributeError.
>> >
>> > (Note that it is valid to have an empty members list, see the= internal
>> > q_empty object as an example. For this reason, we cannot use = the empty
>> > list as a replacement test for full initialization and instea= d rely on
>> > the _checked/_check_complete fields.)
>> >
>> > Signed-off-by: John Snow <jsnow@redhat.com>
>> > ---
>> >=C2=A0 scripts/qapi/schema.py | 12 +++++++-----
>> >=C2=A0 1 file changed, 7 insertions(+), 5 deletions(-)
>> >
>> > diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py<= br> >> > index 50ebc4f12de..fb30314741a 100644
>> > --- a/scripts/qapi/schema.py
>> > +++ b/scripts/qapi/schema.py
>> > @@ -20,7 +20,7 @@
>> >=C2=A0 from collections import OrderedDict
>> >=C2=A0 import os
>> >=C2=A0 import re
>> > -from typing import List, Optional
>> > +from typing import List, Optional, cast
>> >
>> >=C2=A0 from .common import (
>> >=C2=A0 =C2=A0 =C2=A0 POINTER_SUFFIX,
>> > @@ -449,7 +449,7 @@ def __init__(self, name, info, doc, ifcon= d, features,
>> >=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 self.base =3D None
>> >=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 self.local_members =3D loca= l_members
>> >=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 self.variants =3D variants<= br> >> > -=C2=A0 =C2=A0 =C2=A0 =C2=A0 self.members =3D None
>> > +=C2=A0 =C2=A0 =C2=A0 =C2=A0 self.members: List[QAPISchemaObj= ectTypeMember]
>> >=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 self._check_complete =3D Fa= lse
>> >
>> >=C2=A0 =C2=A0 =C2=A0 def check(self, schema):
>> > @@ -482,7 +482,11 @@ def check(self, schema):
>> >=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 for m in self.local_members= :
>> >=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 m.check(schem= a)
>> >=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 m.check_clash= (self.info, seen)
>> > -=C2=A0 =C2=A0 =C2=A0 =C2=A0 members =3D seen.values()
>> > +
>> > +=C2=A0 =C2=A0 =C2=A0 =C2=A0 # check_clash works in terms of = the supertype, but local_members
>> > +=C2=A0 =C2=A0 =C2=A0 =C2=A0 # is asserted to be List[QAPISch= emaObjectTypeMember].
>>
>> Do you mean "but self.members is declared as
>> List[QAPISchemaObjectTypeMember]"?
>
> Argh. I meant asserted in the linguistic sense. mypy asserts it to be;= not
> a runtime assertion.
>
> I do this a lot, apparently.

Okay to adjust your comment to my version?

Absolutely, of course!


[...]

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