DSL enhancement proposal

As discussed on Piter Py #5 in person. Here is the proposal discussed with @proofit404 .

Things which we do here:

• Wipe any realization from a story_suite decorated class
• Use a story suite as a context container. Everything mentioned as steps arguments or results is a context member
• Allow defining some context members explicitly as class attributes, see PurchaseProduct.payment_allowed
• Define all steps call signatures and a context member to store its result in
• Allow validating context members consistency using annotations
• Allow validating realization methods signatures in runtime using DI, see dry-python/dependencies
• Allow validating realization methods signatures in import time using a story suite class as a metaclass of the realization class similar to ABCMeta

import decimal
import stories

@stories.story_suite
class PurchaseProduct:
    payment_allowed: bool

    @stories.story
    def purchase(self, user: User, product: Product, shipment_details: ShipmentDetails):
        self.create_order()
        self.calculate_price()
        self.request_payment()
        self.process_payment() if self.payment_allowed else self.reject_payment()
        self.notify_user()

    @stories.step
    def create_order(
        self, user: User, product: Product
    ) -> stories.Success["order", Order]:
        ...

    @stories.step
    def calculate_price(
        self, order: Order
    ) -> stories.Success["price", decimal.Decimal]:
        ...

    @stories.step
    def request_payment(
        self, user: User, order: Order
    ) -> stories.Success["payment_allowed", bool]:
        ...

    @stories.step
    def process_payment(
        self, user: User, price: decimal.Decimal
    ) -> stories.Success["payment_result", PaymentResult]:
        ...

    @stories.step
    def reject_payment(
        self, user: User
    ) -> stories.Success["payment_result", PaymentResult]:
        ...

[proofit404]

I and @sobolevn agreed that some logic in the type hints isn’t the right choice for this library.

Other things listed here are pretty useful. We will implement them eventually but in a different form.

I’ve decided to spit this report into several issues to work on each separately:

• https://github.com/dry-python/stories/issues/86
• https://github.com/dry-python/stories/issues/76
• https://github.com/dry-python/stories/issues/49
• https://github.com/dry-python/stories/issues/89

[lig]

@proofit404 shall we build something in public as a POC maybe?