John Snow <js...@redhat.com> writes: > On Tue, Sep 7, 2021 at 6:44 AM Markus Armbruster <arm...@redhat.com> wrote: > >> John Snow <js...@redhat.com> writes: >> >> > Annotations do not change runtime behavior. >> > >> > This commit adds mostly annotations, but uses a TYPE_CHECKING runtime >> > check to conditionally import dependencies, which only triggers during >> > runs of mypy. >> >> Please add a reference to >> https://mypy.readthedocs.io/en/latest/runtime_troubles.html#import-cycles >> >> > OK. > > >> > Signed-off-by: John Snow <js...@redhat.com> >> > >> > --- >> > >> > TopLevelExpr, an idea from previous drafts, makes a return here in order >> > to give a semantic meaning to check_expr(). The type is intended to be >> > used more in forthcoming commits (pt5c), but I opted to include it now >> > instead of creating yet-another Dict[str, object] type hint that I would >> > forget to change later. >> > >> > Signed-off-by: John Snow <js...@redhat.com> >> > --- >> > scripts/qapi/parser.py | 77 ++++++++++++++++++++++++++---------------- >> > 1 file changed, 48 insertions(+), 29 deletions(-) >> > >> > diff --git a/scripts/qapi/parser.py b/scripts/qapi/parser.py >> > index 3ddde318376..b1e2fa5c577 100644 >> > --- a/scripts/qapi/parser.py >> > +++ b/scripts/qapi/parser.py >> > @@ -18,6 +18,7 @@ >> > import os >> > import re >> > from typing import ( >> > + TYPE_CHECKING, >> > Dict, >> > List, >> > Optional, >> > @@ -30,6 +31,15 @@ >> > from .source import QAPISourceInfo >> > >> > >> > +if TYPE_CHECKING: >> > + # pylint: disable=cyclic-import >> > + # TODO: Remove cycle. [schema -> expr -> parser -> schema] >> > > WRT this todo: you mentioned that you'd prefer having some idea or plan for > how to eliminate the cycle in order to let this band-aid fly. How about > adding a 'doc' member to e.g. QAPISchemaFeature and doing the connection > entirely inside of schema.py, and dropping connect_member() and > connect_feature()? > > Would that be serviceable?
I guess it would. One way to find out. >> > + from .schema import QAPISchemaFeature, QAPISchemaMember >> > + >> > + >> > +#: Represents a single Top Level QAPI schema expression. >> > +TopLevelExpr = Dict[str, object] >> >> Related: _ExprValue below, and _JSONObject in expr.py. The latter's >> comment gives the best rationale (except I don't get "the purpose of >> this module is to interrogate that type"). >> >> > in expr.py, the purpose of that module (expr) is explicitly to interrogate > (check, validate) the shape of arbitrary JSON objects. I am saying that a > more strict definition specifically here in expr.py is not necessary > because the entire purpose of expr.py is to, at runtime, verify the shape > of any such variables that might be annotated that way. I am drawing some > distinction to introspect.py, where we're generating that data ourselves -- > the stronger types are more viable there, because we know what they are > already. Let me try to write a clearer comment: # Deserialized JSON objects as returned by the parser. # This is a actually Dict[str, _JSONValue], where _JSONValue is # Union[bool, str, List[Self], Dict[str, Self]]. Since mypy lacks # recursive types, we can't define _JSONValue, and use object # instead. Sad. _JSONObject = Dict[str, object] > (again, sorry about mypy's lack of recursive typing, I hate it too, I > promise) We got to play the hand we've been dealt. >> I think we'd like to have >> >> * A recursive type for JSON value (in our bastardized version of JSON) >> >> This is Union of bool, str, List[Self], Dict[str, Self]. It's what >> .get_expr() returns. >> >> Since mypy can't do recursive, we approximate with _ExprValue. >> >> * A recursive type for JSON object >> >> This is the Dict branch of the above. It's what check_keys() & >> friends take as argument. >> >> We approximate with _JSONObject. >> >> Same for the List branch would make sense if we had a use for the >> type. >> >> * A recursive type for TOP-LEVEL-EXPR >> >> Actually the same type as the previous one, to be used only for the >> schema's top-level expressions. It's the elements of >> QAPISchemaParser.exprs[], and what check_exprs() takes as argument. >> >> We approximate with TopLevelExpr, but so far use it only for >> check_exprs(). >> >> Doesn't really improve type checking, but may serve as documentation. >> >> > That's the intended effect here -- to help highlight which functions > operate on those top-level expressions, and which might be invoked in more > arbitrary cases. > Consider also a hypothetical TOP-LEVEL-EXPR that is actually a bona-fide > object with additional metadata, too. In these cases, the type really will > be different. > > >> Shouldn't these types be all defined in one place, namely right here? >> Bonus: we need to explain the mypy sadness just once then. >> >> Shouldn't their names be more systematic? _ExprValue, _JSONObject and >> TopLevelExpr hardly suggest any relation... >> >> > I drop _JSONObject in pt5c, it was a stop-gap. For the rest, I'll see about > a more rigorous consolidation now that we're this far in. > > pt5c was intended as a "cleanup" step that did some of that consolidation > of nearly-redundant types; but I wanted all of parser.py under the mypy gun > *first*. > Will you take a raincheck here and we'll focus on the consolidation in the > next series? I agree it's worth doing. Works for me. > (I can add a 'FIXME' that will 100% need to be fixed before I move > scripts/qapi under python/qemu/qapi -- the linter config there prohibits > them, so you can be sure I can't ignore it.) Makes sense.