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Add annotated support for the provider and added named provider #285

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Add annotated support for the provider and added named provider #285

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33 changes: 32 additions & 1 deletion injector/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1367,6 +1367,23 @@ def provider(function: CallableT) -> CallableT:
return function


def named_provider(name: str) -> CallableT:
"""Decorator for :class:`Module` methods, creating annoted type a of a type.

>>> class MyModule(Module):
... @named_provider("first")
... def provide_name(self) -> str:
... return 'Bob'

"""

def decorator(function: CallableT):
_mark_named_provider_function(function, name, allow_multi=False)
return function

return decorator
Comment on lines +1370 to +1384
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@davidparsson davidparsson Nov 8, 2025

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I'm not convinced that this alternative way of declaring a provider is worth the extra maintenance it introduces. Do you have any arguments behind introducing it?

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@SatwikcoolAgrawal SatwikcoolAgrawal Nov 9, 2025 •
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The reason for adding this was to replicate the @Named annotated functionality from Guice — allowing us to bind and inject a specific instance among multiple instances of the same interface.
Also, considering how @multiprovider works, I wanted to avoid using a dictionary lookup pattern to retrieve the instance by key.

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@davidparsson davidparsson Nov 9, 2025

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Right. I'm still not convinced though.

It has been a while since Java was my primary language, but isn't the presence of @Named in Guice motivated by the absence of a language supported way of declaring annotated types? Since that is supported natively in Python, I think this only adds a less intuitive way to declare the same thing.

I however still happy to merge the other fix in this PR if you're willing to split it.

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@SatwikcoolAgrawal SatwikcoolAgrawal Nov 9, 2025 •
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Right, the only purpose this would serve is to replicate the same pattern used in Guice, which can already be achieved using Annotated. So, there isn’t much of a use case for adding this.
We can close this PR.

You can check the split PR created for the other fix here:
#286

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@davidparsson davidparsson Nov 9, 2025

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Thank you!



def multiprovider(function: CallableT) -> CallableT:
"""Like :func:`provider`, but for multibindings. Example usage::

Expand All @@ -1390,7 +1407,7 @@ def provide_strs_also(self) -> List[str]:
def _mark_provider_function(function: Callable, *, allow_multi: bool) -> None:
scope_ = getattr(function, '__scope__', None)
try:
annotations = get_type_hints(function)
annotations = get_type_hints(function, include_extras=True)
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@davidparsson davidparsson Nov 8, 2025

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Is this what allows for a @provider to return things like Annotated[str, 'first']?

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@SatwikcoolAgrawal SatwikcoolAgrawal Nov 9, 2025

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Yes, adding include_extras=True ensures that metadata inside Annotated types is preserved when fetching type hints. Without it, only the base type (e.g., str) was returned, causing the internal _punch_through_alias check for _AnnotatedAlias to never trigger.

Example:

from typing import Annotated, get_type_hints

def f() -> Annotated[str, 'first']:
    ...

print(get_type_hints(f))
# {'return': <class 'str'>}

print(get_type_hints(f, include_extras=True))
# {'return': typing.Annotated[str, 'first']}

The internal logic in _punch_through_alias already handles checking for _AnnotatedAlias:

elif isinstance(type_, _AnnotatedAlias) and getattr(type_, '__metadata__', None) is not None:
    return type_.__origin__

but the metadata was being stripped before, so this change fixes that.

except NameError:
return_type = '__deferred__'
else:
Expand All @@ -1399,6 +1416,20 @@ def _mark_provider_function(function: Callable, *, allow_multi: bool) -> None:
function.__binding__ = Binding(return_type, inject(function), scope_) # type: ignore


def _mark_named_provider_function(function: Callable, name: str, *, allow_multi: bool) -> None:
scope_ = getattr(function, '__scope__', None)
try:
annotations = get_type_hints(function, include_extras=True)
except NameError:
return_type = '__deferred__'
else:
raw_return_type = annotations['return']
return_type = Annotated[raw_return_type, name]

_validate_provider_return_type(function, cast(type, return_type), allow_multi)
function.__binding__ = Binding(return_type, inject(function), scope_)


def _validate_provider_return_type(function: Callable, return_type: type, allow_multi: bool) -> None:
origin = _get_origin(_punch_through_alias(return_type))
if origin in {dict, list} and not allow_multi:
Expand Down
33 changes: 33 additions & 0 deletions injector_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -55,6 +55,7 @@
Error,
UnknownArgument,
InvalidInterface,
named_provider,
)


Expand Down Expand Up @@ -2032,3 +2033,35 @@ class MyClass:
injector = Injector([configure])
instance = injector.get(MyClass)
assert instance.foo == 123


def test_module_provider_with_annotated():
class MyModule(Module):
@provider
def provide_first(self) -> Annotated[str, 'first']:
return 'Bob'

@provider
def provide_second(self) -> Annotated[str, 'second']:
return 'Iger'

module = MyModule()
injector = Injector(module)
assert injector.get(Annotated[str, 'first']) == 'Bob'
assert injector.get(Annotated[str, 'second']) == 'Iger'


def test_module_named_provider():
class MyModule(Module):
@named_provider('first')
def provide_first(self) -> str:
return 'Bob'

@named_provider('second')
def provide_second(self) -> str:
return 'Iger'

module = MyModule()
injector = Injector(module)
assert injector.get(Annotated[str, 'first']) == 'Bob'
assert injector.get(Annotated[str, 'second']) == 'Iger'