Add opcall

Not sure what to call this, but for now I’ll refer to it as opcall()

Right now, pcall is really hard to use well. To demonstrate this, let’s describe a simple function that might error:

function foo(x: number) {
	if (x > 0) {
		return math.sqrt(x);
	} else {
		throw "x must be more than 0!";
	}
}

If we use pcall normally, it would look like this:

const [success, valueOrError] = pcall(foo, 1);
if (success) {
	valueOrError; // string | number
} else {
	valueOrError; // string | number
}

This isn’t good because valueOrError doesn’t have good types.

You could also try not destructuring the pcall return immediately:

const result = pcall(foo, 1);
if (result[0]) {
	const value = result[1]; // number
} else {
	const errorMsg = result[1]; // string
}

That’s better, but it’s not very ergonomic to use if (result[0]) {. It’s also not really clear when reading the code what you’re doing there.

I propose a new version of pcall that would have the following signature:

declare function opcall<T, U extends Array<any>>(
	cb: (...args: U) => T,
	...args: U
): { success: true; value: T } | { success: false; error: string };

And it’s usage would look like:

const result = opcall(foo, 1);
if (result.success) {
	result.value; // number
} else {
	result.error; // string
}

[osyrisrblx]

inspired by PHP: real_pcall

[Validark]

opcall - object pcall epcall - explicit pcall vpcall - verbose pcall dpcall - dictionary pcall tpcall - table pcall or toilet paper call