provide default for a dependencies container from another dependencies container

[shaunc]

Here is a case that is sort of a mix of other recipes you have provided: I would like to provide a default value for a dependencies container by taking it from another dependencies container:

from dependency_injector import containers, providers

class PV(containers.DeclarativeContainer):

    foo = providers.Object("foo")

PV_SPEC = dict(foo = providers.Dependency(instance_of = str))

class HasPV(containers.DeclarativeContainer):

    pv = providers.DependenciesContainer(**PV_SPEC)

HasPVSpec = dict(pv = providers.DependenciesContainer(**PV_SPEC))

class HasPV2(containers.DeclarativeContainer):

    has_pv = providers.DependenciesContainer(**HasPVSpec)
    pv = providers.DependenciesContainer(**PV_SPEC)
    pv.override(has_pv.pv)

This gives:

src/dependency_injector/providers.pyx in dependency_injector.providers.DependenciesContainer.override()

src/dependency_injector/providers.pyx in dependency_injector.providers.DependenciesContainer._override_providers()

src/dependency_injector/providers.pyx in dependency_injector.providers.Provider.override()

Error: Provider <dependency_injector.providers.Dependency(<class 'str'>) at 0x7fda702c96d0> could not be overridden with itself

[shaunc]

Also tried:

...
HasPVSpec = dict(pv = providers.Dependency(instance_of=containers.DynamicContainer))

class HasPV2(containers.DeclarativeContainer):

    has_pv = providers.DependenciesContainer(**HasPVSpec)
    pv = providers.DependenciesContainer(**PV_SPEC)
    pv.override(has_pv.pv.provided)

Without the "provided" this gives AttributeError: 'dependency_injector.providers.Dependency' object has no attribute 'providers', With the "provided" the error is Error: Dependency is not defined

Update -- sure would be nice if DependenciesContainer took an optional "instance_of" -- even if the instance bound wasn't an actual instance (it could use declarative_parent to sniff for the instance class). Then it wouldn't be necessary to maintain these specs, and also could type check on binding.

[rmk135]

Didn't get to that one today. Will take a look tomorrow.

[rmk135]

Seems #357 feature helps to resolve this one too:

from dependency_injector import containers, providers


class PV(containers.DeclarativeContainer):

    foo = providers.Object('foo')


class HasPV(containers.DeclarativeContainer):

    pv = providers.DependenciesContainer(**PV.dependencies)


class HasPV2(containers.DeclarativeContainer):

    has_pv = providers.DependenciesContainer(**HasPV.dependencies)
    pv = providers.DependenciesContainer(**PV.dependencies)
    pv.override(has_pv.pv)


if __name__ == '__main__':
    haspv2 = HasPV2(pv=PV(foo='bar'))
    print(haspv2.pv.foo())  # prints: bar

What do you think?

[shaunc]

Looks good too! -- Thanks!

[rmk135]

Good, thanks!