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Thu, 4 Feb 2021 16:37:45 +0100 (CET) From: Markus Armbruster To: Eduardo Habkost Subject: Re: [PATCH v4 08/14] qapi/introspect.py: create a typed 'Annotated' data strutcure References: <20210202174651.2274166-1-jsnow@redhat.com> <20210202174651.2274166-9-jsnow@redhat.com> <878s85tdh3.fsf@dusky.pond.sub.org> <20210203215026.GB126021@habkost.net> Date: Thu, 04 Feb 2021 16:37:45 +0100 In-Reply-To: <20210203215026.GB126021@habkost.net> (Eduardo Habkost's message of "Wed, 3 Feb 2021 16:50:26 -0500") Message-ID: <87a6sjdet2.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 2.84 on 10.5.11.23 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-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=-0.351, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, 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: Michael Roth , John Snow , qemu-devel@nongnu.org, Cleber Rosa Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Eduardo Habkost writes: > On Wed, Feb 03, 2021 at 03:47:36PM +0100, Markus Armbruster wrote: >> John Snow writes: >> >> > Presently, we use a tuple to attach a dict containing annotations >> > (comments and compile-time conditionals) to a tree node. This is >> > undesirable because dicts are difficult to strongly type; promoting it >> > to a real class allows us to name the values and types of the >> > annotations we are expecting. >> > >> > In terms of typing, the Annotated type serves as a generic container >> > where the annotated node's type is preserved, allowing for greater >> > specificity than we'd be able to provide without a generic. >> > >> > Signed-off-by: John Snow > [...] >> > +class Annotated(Generic[_NodeT]): >> > + """ >> > + Annotated generally contains a SchemaInfo-like type (as a dict), >> > + But it also used to wrap comments/ifconds around scalar leaf values, >> > + for the benefit of features and enums. >> > + """ >> > + # Remove after 3.7 adds @dataclass: >> >> Make this >> >> # TODO Remove after Python 3.7 ... >> >> to give us a fighting chance to remember. >> >> > + # pylint: disable=too-few-public-methods >> > + def __init__(self, value: _NodeT, ifcond: Iterable[str], >> > + comment: Optional[str] = None): >> >> Why not simply value: _value? > > Example: > x = C(1) > y: C[int] > y = C('x') # mistake > > Declaring value as _NodeT does: > - Make the inferred type of x be Annotated[int]. > - Catch the mistake above. I smell overengineering. I may well be wrong. Without doubt, there are uses for using the type system for keeping SomeGenericType[SomeType] and SomeGenericType[AnotherType] apart. But what do we gain by keeping the Annotated[T] for the possible T apart? _tree_to_qlit() doesn't care: it peels off the wrapper holding ifcond and comment, and recurses for the JSON so wrapped. Regardless of what was wrapped, i.e. what kind of T we got. Heck, it works just fine even if you wrap your JSON multiple times. It doesn't give a hoot whether that makes sense. Making sense is the caller's business. So what does care? Or am I simply confused? PS: As far as I can tell, _tree_to_qlit() doesn't give a hoot whether a dictionary's values are wrapped, either.