Add more strict types and better inference

[Kalin8900]

Hello everyone.

I would like to propose an extension to the current solution to introduce better type inference and type safety.

Please let me know what you think. If you find it useful, I will update the documentation.

[engelmi]

Hi @Kalin8900, thank you for your contribution! I am currently a bit swamped with work, but I'll definitely have look at it the next days.

[engelmi]

Hi @Kalin8900,
what do you want to achieve with the type-safety and where do you want to have it?
In general, I like the idea of using generics to pin down the types. But at the same time the API gets quite a bit more complex, I think. And, although this seems feasible by using a decorator, when using a more general Pointcut, e.g. .*, it is not applicable.

So I am wondering if it is sufficient for your use case to have the "type-safety" on the AspectContext and not type-check if the method the aspect is applied on has the required parameter/return/error types.
So what we could do is sth like this:

// make the Aspects context generic with the default AspectContext 
export interface Aspect<T extends AspectContext = AspectContext> {
    execute(ctx: T): any;
}

export interface AspectContext {
    target: any;
    methodName: string;
    functionParams: any[];
    returnValue: any;
    error: any;
};

// ...

// specify a custom context with a number as return type
interface SpecificAspectContext extends AspectContext {
    target: any;
    methodName: string;
    functionParams: any[];
    returnValue: number;
    error: any;
}
class SpecificAspect implements Aspect {
    execute(ctx: SpecificAspectContext) {
        executeHasBeenCalled = true;
        ctx.returnValue = 2;  // works
        ctx.returnValue = "2"; // error
    }
}
class YetAnotherSampleClass {
    @UseAspect(Advice.After, SpecificAspect)
    public doIt(): number {
        return 1;
    }
}

This way you can pretend to work with specific types in the Aspects execute, but since we don't evaluate it on the decorator, it might be off and the user/developer needs to be careful still. What do you think?

[Kalin8900]

Hello @engelmi!

The main thing I would like to achieve is having the type check on the decorator level. I don't see a point of adding it only on the Aspect level, because you can have unexpected behaviors then. Maybe there is a way to combine the decorator level check if specifying custom context?