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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 80486C47077 for ; Thu, 11 Jan 2024 09:34:22 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rNrRk-0004kl-D8; Thu, 11 Jan 2024 04:33:56 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rNrRi-0004kL-NT for qemu-devel@nongnu.org; Thu, 11 Jan 2024 04:33:54 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rNrRf-0001F1-IO for qemu-devel@nongnu.org; Thu, 11 Jan 2024 04:33:54 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1704965628; 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=AcQHZ7lV88685vs3PP8OIvSJtk39y7HViWYg9kFtC+4=; b=NTwfpNJ5iOqEANybEJQ//5YMwx8wK/a/PvucvFYoWw7TwVjMeNnLQgCGazFWxIL1u1whZP NE54HlohF0LWRixRlbdydfu/zTi33sUlheNWgMrKz03XY1x1rctTk09nDTk+ilJBDIqzmf mzyuMC5UIgGvod71jUuRDmN7pmZZBYs= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-126-y9gUHfosPrOgacIx_9YMHw-1; Thu, 11 Jan 2024 04:33:45 -0500 X-MC-Unique: y9gUHfosPrOgacIx_9YMHw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id E60D51C04351; Thu, 11 Jan 2024 09:33:44 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.71]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A76F83C25; Thu, 11 Jan 2024 09:33:44 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id A0A9021E6682; Thu, 11 Jan 2024 10:33:43 +0100 (CET) From: Markus Armbruster To: John Snow Cc: qemu-devel , Peter Maydell , Michael Roth Subject: Re: [PATCH 11/19] qapi/schema: fix QAPISchemaArrayType.check's call to resolve_type In-Reply-To: (John Snow's message of "Wed, 10 Jan 2024 14:33:05 -0500") References: <20231116014350.653792-1-jsnow@redhat.com> <20231116014350.653792-12-jsnow@redhat.com> <874jhedjv0.fsf@pond.sub.org> <87wmu84o6a.fsf@pond.sub.org> Date: Thu, 11 Jan 2024 10:33:43 +0100 Message-ID: <87jzog1afc.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.1 Received-SPF: pass client-ip=170.10.133.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -38 X-Spam_score: -3.9 X-Spam_bar: --- X-Spam_report: (-3.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.774, 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, T_SCC_BODY_TEXT_LINE=-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 John Snow writes: > On Thu, Nov 23, 2023, 8:03 AM Markus Armbruster wrote: > >> John Snow writes: >> >> > On Wed, Nov 22, 2023 at 7:59=E2=80=AFAM Markus Armbruster wrote: >> >> >> >> John Snow writes: >> >> >> >> > There's more conditionals in here than we can reasonably pack into a >> >> > terse little statement, so break it apart into something more> expl= icit. >> >> > >> >> > (When would a built-in array ever cause a QAPISemError? I don't kno= w, >> >> > maybe never - but the type system wasn't happy all the same.) >> >> > >> >> > Signed-off-by: John Snow >> >> > --- >> >> > scripts/qapi/schema.py | 11 +++++++++-- >> >> > 1 file changed, 9 insertions(+), 2 deletions(-) >> >> > >> >> > diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py >> >> > index 462acb2bb61..164d86c4064 100644 >> >> > --- a/scripts/qapi/schema.py >> >> > +++ b/scripts/qapi/schema.py >> >> > @@ -384,9 +384,16 @@ def need_has_if_optional(self): >> >> > >> >> > def check(self, schema): >> >> > super().check(schema) >> >> > + >> >> > + if self.info: >> >> > + assert self.info.defn_meta # guaranteed to be set by>= expr.py >> >> > + what =3D self.info.defn_meta >> >> > + else: >> >> > + what =3D 'built-in array' >> >> > + >> >> > self._element_type =3D schema.resolve_type( >> >> > - self._element_type_name, self.info, >> >> > - self.info and self.info.defn_meta) >> >> > + self._element_type_name, self.info, what >> >> > + ) >> 0>> > assert not isinstance(self.element_type, QAPISchemaArrayT= ype) >> >> > >> >> > def set_module(self, schema): >> >> >> >> What problem are you solving here? >> >> >> > >> > 1. "self.info and self.info.defn_meta" is the wrong type ifn't self.in= fo >> >> self.info is Optional[QAPISourceInfo]. >> >> When self.info, then self.info.defn_meta is is Optional[str]. >> >> Naive me expects self.info and self.info.defn_meta to be Optional[str]. >> Playing with mypy... it seems to be Union[QAPISourceInfo, None, str]. >> Type inference too weak. >> > > I think my expectations match yours: "x and y" should return either x or = y, > so the resulting type would naively be Union[X | Y], which would indeed be > Union[QAPISourceInfo | None | str], but: > > If QAPISourceInfo is *false-y*, but not None, it'd be possible for the > expression to yield a QAPISourceInfo. mypy does not understand that > QAPISourceInfo can never be false-y. > > (That I know of. Maybe there's a trick to annotate it. I like your soluti= on > below better anyway, just curious about the exact nature of this > limitation.) > > >> > 2. self.info.defn_meta is *also* not guaranteed by static types >> >> Yes. We know it's not None ("guaranteed to be set by expr.py"), but the >> type system doesn't. >> > > Mmhmm. > > >> > ultimately: we need to assert self.info and self.info.defn_meta both; >> > but it's possible (?) that we don't have self.info in the case that >> > we're a built-in array, so I handle that. >> >> This bring us back to the question in your commit message: "When would a >> built-in array ever cause a QAPISemError?" Short answer: never. > > Right, okay. I just couldn't guarantee it statically. I knew this patch w= as > a little bananas, sorry for tossing you the stinkbomb. No need to be sorry! Feels like an efficient way to collaborate with me. >> Long answer. We're dealing with a *specific* QAPISemError here, namely >> .resolve_type()'s "uses unknown type". If this happens for a built-in >> array, it's a programming error. >> >> Let's commit such an error to see what happens: stick >> >> self._make_array_type('xxx', None) >> >> Dies like this: >> >> Traceback (most recent call last): >> File "/work/armbru/qemu/scripts/qapi/main.py", line 94, in main >> generate(args.schema, >> File "/work/armbru/qemu/scripts/qapi/main.py", line 50, in generate >> schema =3D QAPISchema(schema_file) >> ^^^^^^^^^^^^^^^^^^^^^^^ >> File "/work/armbru/qemu/scripts/qapi/schema.py", line 938, in >> __init__ >> self.check() >> File "/work/armbru/qemu/scripts/qapi/schema.py", line 1225, in che= ck >> ent.check(self) >> File "/work/armbru/qemu/scripts/qapi/schema.py", line 373, in check >> self.element_type =3D schema.resolve_type( >> ^^^^^^^^^^^^^^^^^^^^ >> File "/work/armbru/qemu/scripts/qapi/schema.py", line 973, in >> resolve_type >> raise QAPISemError( >> qapi.error.QAPISemError: >> >> During handling of the above exception, another exception occurred: >> >> Traceback (most recent call last): >> File "/work/armbru/qemu/scripts/qapi-gen.py", line 19, in >> sys.exit(main.main()) >> ^^^^^^^^^^^ >> File "/work/armbru/qemu/scripts/qapi/main.py", line 101, in main >> print(err, file=3Dsys.stderr) >> File "/work/armbru/qemu/scripts/qapi/error.py", line 41, in __str__ >> assert self.info is not None >> ^^^^^^^^^^^^^^^^^^^^^ >> AssertionError >> >> Same before and after your patch. The patch's change of what=3DNone to >> what=3D'built-in array' has no effect. >> >> Here's a slightly simpler patch: >> >> diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py >> index 46004689f0..feb0023d25 100644 >> --- a/scripts/qapi/schema.py >> +++ b/scripts/qapi/schema.py >> @@ -479,7 +479,7 @@ def check(self, schema: QAPISchema) -> None: >> super().check(schema) >> self._element_type =3D schema.resolve_type( >> self._element_type_name, self.info, >> - self.info and self.info.defn_meta) >> + self.info.defn_meta if self.info else None) >> > > Yep. > > assert not isinstance(self.element_type, QAPISchemaArrayType) >> >> def set_module(self, schema: QAPISchema) -> None: >> @@ -1193,7 +1193,7 @@ def resolve_type( >> self, >> name: str, >> info: Optional[QAPISourceInfo], >> - what: Union[str, Callable[[Optional[QAPISourceInfo]], str]], >> + what: Union[None, str, Callable[[Optional[QAPISourceInfo]], str= ]], >> ) -> QAPISchemaType: >> typ =3D self.lookup_type(name) >> if not typ: >> >> The first hunk works around mypy's type inference weakness. It rewrites >> >> A and B >> >> as >> >> B if A else A >> >> and then partially evaluates to >> >> B if A else None >> >> exploiting the fact that falsy A can only be None. It replaces this >> patch. > > Sounds good to me! Does it need a comment explaining the somewhat awkward coding? Probably not. >> The second hunk corrects .resolve_type()'s typing to accept what=3DNone. >> It's meant to be squashed into PATCH 16. >> >> What do you think? >> > > I'm on my mobile again, but at a glance I like it. Except that I'm a litt= le > reluctant to allow what to be None if this is the *only* caller known to > possibly do it, and only in a circumstance that we assert elsewhere that = it > should never happen. > > Can we do: > > what =3D self.info.defn_meta if self.info else None > assert what [is not None] # Depending on taste > > instead? > > No sem error, no new unit test needed, assertion provides the correct fra= me > of mind (programmer error), stronger typing on resolve_type. > > (I really love eliminating None when I can as a rule because I like how > much more it tells you about the nature of all callers, it's a much > stronger decree. Worth pursuing where you can, IMO, but I'm not gonna die > on the hill for a patch like this - just sharing my tendencies for > discussion.) Suggest you post the patch, so I can see it more easily in context.