Hi everyone, we've come across a mypy error that shouldn't be an error AFAICT. Shouldn't a function returning a
Dict[str, str] be compatible with an argument that expects a function returning a Dict[str, Union[str, int]? Here's the full code example:from typing import Callable, Dict, Union
class Foo:
def __init__(self, bar_fn: Callable[[int], Dict[str, Union[str, int]]]):
self.bar_fn = bar_fn
def get_dict(self) -> Dict[str, Union[str, int]]:
return self.bar_fn(1)
def fn_1(x: int) -> Dict[str, Union[str, int]]:
return {"key1": "value1", "key2": 2}
Foo(bar_fn=fn_1) # This works
def fn_2(x: int) -> Dict[str, str]:
return {"key": "value"}
Foo(bar_fn=fn_2) # This raises the following mypy error:
# [filename].py:23: error: Argument "bar_fn" to "Foo" has incompatible type "Callable[[int], Dict[str, str]]"; expected "Callable[[int], Dict[str, Union[str, int]]]"
4 replies
i'm looking at trying to catch cases where trio has a parameter defaulted to
None and trio-stubs doesn't have that parameter hinted as Optional. https://github.com/python-trio/trio/blob/d203b30f807e43dc9b101de2e52355ebd10b757a/trio/_core/_run.py#L1942 -- https://github.com/python-trio/trio-typing/blob/f32f17b0f242daf2d42407f383ca581d64b6c299/trio-stubs/lowlevel.pyi#L97 i guessed that maybe stubtest would catch this, but it doesn't seem to. is there another approach i should use to find similar cases? or perhaps there is a reason this "can't" be done?
https://mypy.readthedocs.io/en/stable/command_line.html#cmdoption-mypy-no-implicit-optional
Is this not what you need?
@ignormies:matrix.org that's the idea, yeah, but this is checking separate stubs, not a program using the trio library. in fact, having that and running mypy against qtrio which uses trio is exactly what turned this up. i haven't figured out how to get that to be enforced against the combination of package and stubs.
trio has a parameter defaulted to
Noneand trio-stubs doesn't have that parameter hinted asOptional
In this context, would the problem be in trio, or in trio-stubs?
but just reporting the discrepancy would leave me a chance to pick which to change. so for the goal of catching this scenario, it doesn't matter which is wrong, i think.
How can I trace a possible bug where class attribute with name
defaults would lose its typing when used in inherited class? This only applies to an attribute with the name defaults.
Never mind, figured it out
It’s not really clear in the mypy release note blog post
@hauntsaninja should stubtest check the package and the stubs against each other when it comes to implicit optional hints? context is 9 messages up, but trio has a parameter
=None and the stubs have : trio.abc.Clock = .... seems like it would be good to have some tool or another able to find this discrepancy.
I'm trying to dynamically add a method to ca ClassDef in a plugin hook.
What I can't work out is: how to construct new Function definitions.
Because those function definitions need types in their args.
But I don't know how to get arbitrary types
And
mypy.nodes.TypeInfo
This message was deleted
It'd be nice if there was autodocumentation for the plugin api
6 replies
Basically, I was getting really annoyed with how a lot of python web developers just do ad hoc interfaces between services. And I wanted to see if I could create a metaprogrammed OpenAPI client; but one where I could also use MyPy to verify you are using the API correctly.
@altendky stubtest does check that default values are a subtype of the arg's type hint
maybe the issue is that your stub is decorated?
@hauntsaninja https://gist.github.com/altendky/3327ab219a04e27f628b92aa6c480d8a here's the minimal example. i can certainly file a ticket if you think it is appropriate.
also, this isn't a pressing issue. at this point i'm starting to just merge the stubs into the package so this is relevant primarily in the context of just improving (i think?
:]) stubtest.
@altendky if i change your repro to create a pyi file instead of a py file in package-stubs, i get:
error: package.f is inconsistent, runtime argument "p" has a default value of type None, which is incompatible with stub argument type builtins.int
Stub: at line 1
def (p: builtins.int =)
Runtime: at line 1 in file /Users/shantanu/tmp/lol/package/__init__.py
def (p=None)altendky @altendky sighs
i'll explore the difference between that and the actual situation. thanks.
Hi, can anyone help me understand what is wrong with my annotations on my code https://bpa.st/MGSOM . mypy thinks there is an error on L8 but I dont understand what is wrong. It looks like mypy correctly restricts to one type of a Union when it enters an if block but it throws that knowledge away when it enters a locally defined function (compare L5 & L7). Is this a mypy bug?
from typing import Union
def foo(X: Union[int, str]) -> bool:
if isinstance(X, str):
reveal_type(X) # str
def g(y: int) -> bool:
reveal_type(X) # Union[int, str]
return len(X) > y # <<<<< error: Argument 1 to "len" has incompatible type "Union[int, str]"; expected "Sized"
return g(10)
reveal_type(X) # int
return bool(X)
Anyone please