| Message ID | 20210422030720.3685766-8-jsnow@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | qapi: static typing conversion, pt5a | expand |
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?
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
John Snow <jsnow@redhat.com> writes: > 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 Yes, None for tokens like '{'. > 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. I understand that mypy can't prove implications like if self.tok == "'", then self.val is a str. What I'm curious about is why key needs to be known to be str here. Hmm, is it so return expr type-checks once you add -> OrderedDict[str, object] to the function?
On 4/27/21 2:13 AM, Markus Armbruster wrote: > John Snow <jsnow@redhat.com> writes: > >> 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 > > Yes, None for tokens like '{'. > >> 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. > > I understand that mypy can't prove implications like if self.tok == "'", > then self.val is a str. > > What I'm curious about is why key needs to be known to be str here. > Hmm, is it so return expr type-checks once you add -> OrderedDict[str, > object] to the function? > Oh, yes.
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 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(+)