Extract function parameters or change function return type in mapped types

Search Terms

extract function parameters
change function return type

Suggestion

Allow mapped types to change the return type of a function

Use Cases

I am writing a mocking framework. My system under test might be like this:

MyClass{
    myClassFunction(paramOne: string, paramTwo: number): string{}
}

but in my mocking framework I want to do this:

mockedObject
    .withFunction("myClassFunction")
    .withParameters("paramOneValue", 123)
   .wasCalled();

to do the withParameters I need to type a function with the same parameters as defined on my class but with a different return type.

Checklist

My suggestion meets these guidelines:
[ ] This wouldn't be a breaking change in existing TypeScript / JavaScript code
[ ] This wouldn't change the runtime behavior of existing JavaScript code
[ ] This could be implemented without emitting different JS based on the types of the expressions
[ ] This isn't a runtime feature (e.g. new expression-level syntax)

Commencez par examiner les capacités de TypeScript en matière de mapped types et de function types à partir de l’exemple de mocking-framework. Déterminez comment exprimer l’extraction des paramètres et le remplacement du type de retour tout en préservant le comportement existant de TypeScript et de JavaScript. La tâche est terminée lorsque la transformation de type demandée est prise en charge et que les paramètres de la fonction mockée de l’exemple sont correctement vérifiés.