Re: [PATCH 07/22] qapi/parser: assert object keys are strings

[John Snow]

On 4/25/21 3:27 AM, Markus Armbruster wrote:
> John Snow <jsnow@redhat.com> writes:
>
> > The single quote token implies the value is a string. Assert this to be
> > the case.
> >
> > Signed-off-by: John Snow <jsnow@redhat.com>
> > ---
> >   scripts/qapi/parser.py | 2 ++
> >   1 file changed, 2 insertions(+)
> >
> > diff --git a/scripts/qapi/parser.py b/scripts/qapi/parser.py
> > index 6b443b1247e..8d1fe0ddda5 100644
> > --- a/scripts/qapi/parser.py
> > +++ b/scripts/qapi/parser.py
> > @@ -246,6 +246,8 @@ def get_members(self):
> >               raise QAPIParseError(self, "expected string or '}'")
> >           while True:
> >               key = self.val
> > +            assert isinstance(key, str)  # Guaranteed by tok == "'"
> > +
> >               self.accept()
> >               if self.tok != ':':
> >                   raise QAPIParseError(self, "expected ':'")
>
> The assertion is correct, but I wonder why mypy needs it.  Can you help?

The lexer value can also be True/False (Maybe None? I forget) based on 
the Token returned. Here, since the token was the single quote, we know 
that value must be a string.

Mypy has no insight into the correlation between the Token itself and 
the token value, because that relationship is not expressed via the type 
system.

--js