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Need plugin hooks for functions/methods #6760
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I like this idea, this will allow supporting some common dynamic features.
This will likely require local lookup functions to the public API (currently it is there on
SemanticAnalyzerbut not onSemanticAnalyzerPluginInterface).JFI/bump: I wonder if this is only about having
get_function_signature_hook(in line withget_method_signature_hook) - but from a quick test it seems likeget_method_signature_hookalso only gets called for method calls, not definitions.
I've also looked into this because of pytest.Brainstorming:
- We could have a hook that gets called after semantic analysis and before type checking that can adjust the signature of each function/method.
- We could have a signature adjustment hook that gets called before type checking the body of a function. However, this seems more complicated -- for consistency, we also need another hook that gets called for function calls. The benefit here would be that the hook could access inferred types of other functions and attributes.
- We could have a hook that gets called for each module after semantic analysis, which would allow arbitrary changes to module namespaces. However, the implementation would have to be pretty tightly coupled with the mypy symbol table and AST implementation, so this might not the best option. Also, this might not work well with mypy daemon.
Reacted by JonasBrainstorming:
* We could have a hook that gets called after semantic analysis and before type checking that can adjust the signature of each function/method.I was quite suprised this is not already the case, as I understand it exists for classes / methods with the
get_method_signature_hookalready.What's the reasoning behind that decision? What would be needed to add such a hook?
We could have a signature adjustment hook that gets called before type checking the body of a function. However, this seems more complicated -- for consistency, we also need another hook that gets called for function calls. The benefit here would be that the hook could access inferred types of other functions and attributes.
This looks like exactly what I am looking for here: https://gitter.im/python/typing?at=5efa750ee0e5673398e1aa81
TLDR:
@kinded def map_functor( f: Kind[K, T], function: Callable[[T], V], ) -> Kind[K, V]: return f.map(function)
This code currently does not typecheck, because it is not seem to be possible to tell what
Kindis in this context.JFI/bump: I wonder if this is only about having
get_function_signature_hook(in line withget_method_signature_hook) - but from a quick test it seems likeget_method_signature_hookalso only gets called for method calls, not definitions. I've also looked into this because of pytest.Related to this, I found that
get_function_signature_hookis not called in this case (when a function is used as a decorator):import functools @functools.cache def compute(x: int, y: int) -> int: return (x*x + y*y)/(x+y)
but it is called in this case (when a function is used as a function):
import functools def _compute(x: int, y: int) -> int: return (x*x + y*y)/(x+y) compute = functools.cache(_compute)
Is this the expected behavior? IMHO
get_function_signature_hookshould be called also when a function is used as a decorator since decorators are syntactical sugar. Should this be considered a bug?Should this be considered a bug?
Yes, I think this is a bug (but to be clear fixing it will not solve the original issue).
For some frameworks like
pytestit would be useful to have a plugin that works with functions.Currently mypy has decorator hook for classes.
Some ideas for possible hooks:
For example pytest has the following fixture
The fixture is used by name:
db_pathargument here is a calucated the result ofdb_path()fixture call.It is bound by parameter name which is the same as the fixture name.
Adding a type to
db_pathargument is tedious, especially if a fixture returns some complex type likeCallable[[str, int], Awaitable[web.Response]].Technically all needed information can be extracted from fixture definition if the definition is type annotated.
A plugin for pytest would be awesome but as @ilevkivskyi said
mypyneeds a new hook to support it.