fix: guard unsubscripted Variadic type in InputSocket

[axelray-dev]

What's broken

Instantiating a component with a bare Annotated[Iterable, HAYSTACK_VARIADIC_ANNOTATION] annotation (no type argument) crashes with IndexError: tuple index out of range in InputSocket.__post_init__. The crash happens at component instantiation time, bypassing static type checking. For example:

def run(self, inputs: Annotated[Iterable, HAYSTACK_VARIADIC_ANNOTATION]):

raises IndexError inside get_args(get_args(self.type)[0])[0] at line 100.

Why it happens

get_args(Iterable) returns an empty tuple when the iterable has no type argument, so the unconditional [0] index fails.

Fix

Replaced the bare double-index with a guarded version that checks whether get_args() results are non-empty. When the inner type is unsubscripted, raises ComponentError with a clear message: "Variadic input 'inputs' must have a type argument, e.g. Variadic[int]."

Test

Added test_input_socket_variadic_without_type_arg_raises_component_error which creates a component with a bare Annotated[Iterable, HAYSTACK_VARIADIC_ANNOTATION] input and asserts that ComponentError is raised with the expected message.

Fixes #11453

---

This PR was fully generated with an AI assistant. I have reviewed the changes and run the relevant tests.

[vercel]

@axelray-dev is attempting to deploy a commit to the deepset Team on Vercel.

A member of the Team first needs to authorize it.