microsoft
Add support for python descriptor protocol
As of version 0.5.30.0 the language server does not seem to support the python descriptor protocol, that allows definition of functions similar to the @property decorator. The documentation for this on the python docs is https://docs.python.org/3/howto/descriptor.html
Example:
class memoized_property:
def __init__(self, fGet):
self.fGet = fGet
def __get__(self, instance, class_=None):
if instance is None:
return self
instance.__dict__[self.__name__] = res = self.fGet(instance)
return res
class Foo:
@memoized_property
def i_only_run_once(self) -> str:
# long expensive stuff here
return 'once'
foo = Foo()
value = foo.i_only_run_once
value is 'once' here, but the inferred type is the function Foo.i_only_run_once() -> str, since the language server thinks that i_only_run_once is a function.
Calling it foo.i_only_run_once() makes the inferred type be str, but it will obviously cause a runtime error.
Using @property instead of @memoized_property works as expected.
I'm using vscode 1.42.1 and the language server 0.5.30.0
For reference, @property is special cased in the analysis. Custom decorators like this are not supported to this extent, hence why the decorator doesn't have any effect.
I figured as much, since @property is far more common.
It would be nice if it could be supported though.