TypeScript error when trying to provide a stateHandler with setup and teardown

[ghost91-]

Software versions

Please provide at least OS and version of pact-js

• OS: Arch Linux, Ubuntu, Windows (it's irrelevant)
• Consumer Pact library: Pact JS v12.1.2
• Provider Pact library: Pact JS v12.1.2
• Node Version: v20.11.0

Issue Checklist

Please confirm the following:

• I have upgraded to the latest
• I have the read the FAQs in the Readme
• I have triple checked, that there are no unhandled promises in my code and have read the section on intermittent test failures
• I have set my log level to debug and attached a log file showing the complete request/response cycle
• For bonus points and virtual high fives, I have created a reproduceable git repository (see below) to illustrate the problem

Expected behaviour

There are no TypeScript errors when trying to provide a stateHandler with setup and teardown to a Verifier.

Actual behaviour

Trying to provide a stateHandler with setup and teardown results in the following TypeScript error:

error TS2322: Type '{ setup: () => Promise<void>; teardown: () => Promise<void>; }' is not assignable to type 'StateHandler & ((state: string, params?: { [name: string]: string; } | undefined) => Promise<unknown>)'.
  Type '{ setup: () => Promise<void>; teardown: () => Promise<void>; }' is not assignable to type 'StateFuncWithSetup & ((state: string, params?: { [name: string]: string; } | undefined) => Promise<unknown>)'.
    Type '{ setup: () => Promise<void>; teardown: () => Promise<void>; }' is not assignable to type '(state: string, params?: { [name: string]: string; } | undefined) => Promise<unknown>'.
      Type '{ setup: () => Promise<void>; teardown: () => Promise<void>; }' provides no match for the signature '(state: string, params?: { [name: string]: string; } | undefined): Promise<unknown>'.

Steps to reproduce

import { Verifier } from '@pact-foundation/pact';

const verifier = new Verifier({
  stateHandlers: {
    'name of the stateHandler': { setup: async () => {}, teardown: async () => {} } // this line produces a TypeScript error
  }
});

[valkolovos]

I've seen this error as well. It appears to be because VerifierOptions as defined in src/dsl/verifier/types.ts includes both ProxyOptions and MessageProviderOptions which each define stateHandlers differently. I am not very good with Typescript, but the error message thrown indicates that the transpiler is preferring the type definition of stateHandlers defined by MessageProviderOptions over the one provided by ProxyOptions.

[muratkeremozcan]

I have an easy repro.

Pull the repo, install and remove the ts-ignore to reproduce.

https://github.com/muratkeremozcan/pact-js-example-provider/blob/main/src/test-helpers/state-handlers.ts#L66