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Sarj Sarj Sarj Standards

require-public-dependency-contract

Reuse an existing substitutable contract instead of its concrete implementation annotation.

SARJ466 Rule source Tests Catalog JSON

Why

A concrete dependency annotation obstructs substitution even when an existing public contract already has multiple implementations.

Fix

Annotate the dependency with the existing public contract; do not create a new interface.

Examples

Before — flagged Use the existing substitutable publisher contract
app/__init__.py
# package
app/consumer.py
from app.publisher import Publisher, HttpPublisher




class Consumer:
    def __init__(self, publisher: HttpPublisher) -> None:
        self.publisher = publisher


    def run(self) -> None:
        self.publisher.publish()
app/publisher.py
from abc import ABC, abstractmethod




class Publisher(ABC):
    @abstractmethod
    def publish(self) -> None: ...




class HttpPublisher(Publisher):
    def publish(self) -> None: ...




class QueuePublisher(Publisher):
    def publish(self) -> None: ...
After — preferred The consumer already uses the existing contract
app/__init__.py
# package
app/consumer.py
from app.publisher import Publisher, HttpPublisher




class Consumer:
    def __init__(self, publisher: Publisher) -> None:
        self.publisher = publisher


    def run(self) -> None:
        self.publisher.publish()
app/publisher.py
from abc import ABC, abstractmethod




class Publisher(ABC):
    @abstractmethod
    def publish(self) -> None: ...




class HttpPublisher(Publisher):
    def publish(self) -> None: ...




class QueuePublisher(Publisher):
    def publish(self) -> None: ...