Layers

archtool can enforce layer boundaries across your modules, preventing lower-level layers from importing higher-level ones.

Built-in layers

from archtool.layers.default_layers import DomainLayer, ApplicationLayer, InfrastructureLayer

Layer	Allowed to import from
InfrastructureLayer	ApplicationLayer, DomainLayer
ApplicationLayer	DomainLayer
DomainLayer	nothing above itself

Wiring with layers

from archtool.dependency_injector import DependencyInjector
from archtool.global_types import AppModule
from archtool.layers.default_layers import DomainLayer

injector = DependencyInjector(
    modules_list=[AppModule("app.users")],
    layers=[DomainLayer],
)
injector.inject()

If any module violates the layer rules, archtool raises TopLevelLayerUsingException at assembly time — not at runtime when the bug causes an obscure traceback.

Custom layers

Subclass Layer to define your own hierarchy:

from archtool.interfaces.layer import Layer

class PresentationLayer(Layer):
    ...

class BusinessLayer(Layer):
    forbidden = [PresentationLayer]   # business must not import presentation