On Thu, Feb 04, 2021 at 04:37:45PM +0100, Markus Armbruster wrote:
> Eduardo Habkost <ehabk...@redhat.com> writes:
>
> > On Wed, Feb 03, 2021 at 03:47:36PM +0100, Markus Armbruster wrote:
> >> John Snow <js...@redhat.com> 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<T> 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 <js...@redhat.com>
> > [...]
> >> > +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.
To me it's just regular and idiomatic use of Generic.
>
> 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?
I understand this as (valid) criticism of the use of Generic.
If we don't want to make Generic[T1] and Generic[T2] be
different types, there's no point in using Generic at all.
>
> _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?
Those are valid questions. Maybe using Generic will be useful
in the future, but maybe we don't need it right now.
Personally, I don't care either way. I just wish this small
choice don't became another obstacle for doing useful work.
>
>
> PS: As far as I can tell, _tree_to_qlit() doesn't give a hoot whether a
> dictionary's values are wrapped, either.
--
Eduardo
