[issue37923] Combining typing.get_type_hints and inspect.signature

[dmontague]

New submission from dmontague <davwmont at gmail.com>:

I am trying to obtain the output of `inspect.signature`, except with string-valued annotations converted to resolved type hints, similarly to `typing.get_type_hints`.

Is there a good way to do this currently? If not, might this be a good fit for the standard library?

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The straightforward way I see to attempt this would be to call both `typing.get_type_hints` and `inspect.signature` on the callable, and then "merge" the results. However, as far as I can tell, that only works if the provided callable is a function or method (i.e., not a type or a callable class instance).

As an example, if I have an instance of a class with a `__call__` method, and the class was defined in a module with `from __future__ import annotations`, then calling `inspect.signature` on the instances will only return an `inspect.Signature` with type-unaware strings as the annotations for each `inspect.Parameter`. On the other hand, calling `get_type_hints` on the instance will return type hints for the class, rather than for its `__call__` method.

I wouldn't mind manually handling an edge case or two, but the logic used by `inspect.signature` to determine which function will be called seems relatively involved, and so I would ideally like to leverage this same logic while obtaining the type-resolved version signature for the callable.

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messages: 350248
nosy: dmontague, levkivskyi
priority: normal
severity: normal
status: open
title: Combining typing.get_type_hints and inspect.signature
type: enhancement
versions: Python 3.7

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue37923>
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