Mapping provider/customer with description

[ramondepieri]

Have you read the Contributing Guidelines on issues?

• [X] I have read the Contributing Guidelines on issues.

Prerequisites

• [X] I'm using the latest version of pact-python.
• [X] I have read the console error message carefully (if applicable).

Description

I am trying to create a message contract test, but something is going wrong:

RuntimeError:
       An error was raised while verifying the message. The response body is: {"detail":"No matched handler."}

According to tests, the problem is happening in reason of mapping is being made by provider state instead of description

Reproducible demo

No response

Steps to reproduce

Run the consumer:

# consumer.py
from pact import MessageConsumer, Provider

def run_consumer():
    contract = MessageConsumer(
        "my_contract Consumer"
    ).has_pact_with(
        Provider("my_contract Provider"),
        pact_dir="pacts",
    )

    event_data = {
        "invoice_id": "12345",
        "amount": 100.00,
        "currency": "USD"
    }

    contract.given("Create contract").expects_to_receive(
        "An event of contract").with_content(event_data)

    with contract:
        pass

if __name__ == "__main__":
    run_consumer()

Now run the provider:

# provider.py
from pact import MessageProvider

def process_invoice_event(event):
    invoice_id = event.get("invoice_id")
    amount = event.get("amount")
    currency = event.get("currency")

    # Validação simples
    if not invoice_id or amount <= 0:
        return {"status": "error", "message": "Invalid invoice data"}

    print(f"Processing invoice: ID = {invoice_id}, Amount = {amount} {currency}")
    return event

def run_provider():
    simulated_event = {
        "invoice_id": "12345",
        "amount": 100.00,
        "currency": "USD"
    }

    provider = MessageProvider(
        message_providers={
            "An event of contract": lambda: process_invoice_event(simulated_event),
        },
        provider="my_contract Provider",
        pact_dir="pacts",
        consumer="my_contract Consumer",
    )

    with provider:
        provider.verify()

if __name__ == "__main__":
    run_provider()

This error will happens: RuntimeError: An error was raised while verifying the message. The response body is: {"detail":"No matched handler."}

Now change the message_providers, to use "Create contract" string instead of "An event of contract"

Note that now is working

Expected behavior

The mapping should use the description instead of provider state

Actual behavior

RuntimeError: An error was raised while verifying the message. The response body is: {"detail":"No matched handler."}

Your environment

No response

Self-service

• [ ] I'd be willing to fix this bug myself.

[mefellows]

I think if we do fix it, to preserve backwards compatibility we may need to check (map) both the states and the description, and only error if one is not found.

[YOU54F]

This has always been a long-standing bug in the pact-python message pact implementation. You will need to map providerStates to message handlers in Pact-python at the moment.

It is also present in the v3 pact examples.

The consumer side

https://github.com/pact-foundation/pact-python/blob/34f686ff3fc57d48284092925bd5b5ac0b8507c6/examples/tests/test_02_message_consumer.py#L114

These should be swapped.

        pact.given("a request to read test.txt")
        .expects_to_receive("test.txt exists")

to be

        pact.given("test.txt exists")
        .expects_to_receive("a request to read test.txt")

In the message provider, we are incorrectly using the provider state, instead of the description

https://github.com/pact-foundation/pact-python/blob/34f686ff3fc57d48284092925bd5b5ac0b8507c6/examples/tests/v3/test_03_message_provider.py#L35-L44

in the message provider proxy, that is shown in the examples, it does not provide a mechanism to pass the message description

https://github.com/pact-foundation/pact-python/blob/34f686ff3fc57d48284092925bd5b5ac0b8507c6/examples/tests/v3/provider_server.py#L88

Those examples should be updated in V3 as well, to use the description, and not the provider state, for the handler mappings