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Tue, 2 Mar 2021 06:29:46 +0100 (CET) From: Markus Armbruster To: John Snow Subject: Re: [PATCH v3 08/16] qapi/expr.py: add type hint annotations References: <20210223003408.964543-1-jsnow@redhat.com> <20210223003408.964543-9-jsnow@redhat.com> <87wnuwb68s.fsf@dusky.pond.sub.org> <6ce7f875-7598-ed9a-4935-5073ae2b5ec0@redhat.com> Date: Tue, 02 Mar 2021 06:29:46 +0100 In-Reply-To: <6ce7f875-7598-ed9a-4935-5073ae2b5ec0@redhat.com> (John Snow's message of "Thu, 25 Feb 2021 15:54:01 -0500") Message-ID: <874khunmwl.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: -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, 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 , qemu-devel@nongnu.org, Eduardo Habkost , Cleber Rosa Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" John Snow writes: > On 2/25/21 8:56 AM, Markus Armbruster wrote: >> John Snow writes: >> >>> Annotations do not change runtime behavior. >>> This commit *only* adds annotations. >>> >>> Signed-off-by: John Snow >>> Reviewed-by: Eduardo Habkost >>> Reviewed-by: Cleber Rosa >>> --- >>> scripts/qapi/expr.py | 71 ++++++++++++++++++++++++++++--------------- >>> scripts/qapi/mypy.ini | 5 --- >>> 2 files changed, 46 insertions(+), 30 deletions(-) >>> >>> diff --git a/scripts/qapi/expr.py b/scripts/qapi/expr.py >>> index f45d6be1f4c..df6c64950fa 100644 >>> --- a/scripts/qapi/expr.py >>> +++ b/scripts/qapi/expr.py >>> @@ -15,7 +15,14 @@ >>> # See the COPYING file in the top-level directory. >>> >>> import re >>> -from typing import MutableMapping, Optional, cast >>> +from typing import ( >>> + Iterable, >>> + List, >>> + MutableMapping, >>> + Optional, >>> + Union, >>> + cast, >>> +) >>> >>> from .common import c_name >>> from .error import QAPISemError >>> @@ -23,9 +30,10 @@ >>> from .source import QAPISourceInfo >>> >>> >>> -# Expressions in their raw form are JSON-like structures with arbitrary forms. >>> -# Minimally, their top-level form must be a mapping of strings to values. >>> -Expression = MutableMapping[str, object] >>> +# Arbitrary form for a JSON-like object. >>> +_JSObject = MutableMapping[str, object] >>> +# Expressions in their raw form are (just) JSON-like objects. >>> +Expression = _JSObject >> >> We solved a similar, slightly more involved typing problem in >> introspect.py. >> >> Whereas expr.py uses Python dict, list, and scalars to represent the >> output of a JSON parser, introspect.py uses them to represent the input >> of a quasi-JSON formatter ("quasi-JSON" because it spits out a C >> initializer for a C representation of JSON, but that's detail). >> >> introspect.py additionally supports comments and #if conditionals. >> >> This is the solution we're using in introspect.py. The Annotated[] part >> is for comments and conditionals; ignore that. >> >> # This module constructs a tree data structure that is used to >> # generate the introspection information for QEMU. It is shaped >> # like a JSON value. >> # >> # A complexity over JSON is that our values may or may not be annotated. >> # >> # Un-annotated values may be: >> # Scalar: str, bool, None. >> # Non-scalar: List, Dict >> # _value = Union[str, bool, None, Dict[str, JSONValue], List[JSONValue]] >> # >> # With optional annotations, the type of all values is: >> # JSONValue = Union[_Value, Annotated[_Value]] >> # >> # Sadly, mypy does not support recursive types; so the _Stub alias is used to >> # mark the imprecision in the type model where we'd otherwise use JSONValue. >> _Stub = Any >> _Scalar = Union[str, bool, None] >> _NonScalar = Union[Dict[str, _Stub], List[_Stub]] >> _Value = Union[_Scalar, _NonScalar] >> JSONValue = Union[_Value, 'Annotated[_Value]'] >> >> introspect.py then adds some more type aliases to convey meaning: >> >> # These types are based on structures defined in QEMU's schema, so we >> # lack precise types for them here. Python 3.6 does not offer >> # TypedDict constructs, so they are broadly typed here as simple >> # Python Dicts. >> SchemaInfo = Dict[str, object] >> SchemaInfoObject = Dict[str, object] >> SchemaInfoObjectVariant = Dict[str, object] >> SchemaInfoObjectMember = Dict[str, object] >> SchemaInfoCommand = Dict[str, object] >> >> I'm not asking you to factor out common typing. >> >> I'm not even asking you to rework expr.py to maximize similarity. >> >> I am asking you to consider stealing applicable parts from >> introspect.py's comments. >> >> _JSObject seems to serve the same purpose as JSONValue. Correct? >> >> Expression seems to serve a comparable purpose as SchemaInfo. Correct? >> >> [...] >> > > Similar, indeed. > > Without annotations: > > _Stub = Any > _Scalar = Union[str, bool, None] > _NonScalar = Union[Dict[str, _Stub], List[_Stub]] > _Value = Union[_Scalar, _NonScalar] > JSONValue = _Value > > (Or skip the intermediate _Value name. No matter.) > > Though expr.py has no use of anything except the Object form itself, > because it is inherently a validator and it doesn't actually really > require any specific type, necessarily. > > So I only really needed the object form, which we never named in > introspect.py. We actually avoided naming it. > > All I really need is, I think: > > _JSONObject = Dict[str, object] > > with a comment explaining that object can be any arbitrary JSONValue > (within limit for what parser.py is capable of producing), and that the > exact form of such will be evaluated by the various check_definition() > functions. > > Is that suitable, or do you have something else in mind? Sounds good.