How to optimise Debug.assert

[mvaligursky]

currently we have this implementation

static assert(assertion, ...args) {
        if (!assertion) {
            console.error('ASSERT FAILED: ', ...args);
        }
    }

And typically it's called like this:

Debug.assert(condition, `Templated string with arguments ${argument}.`);

The problem here is that the templated string gets expanded before being passed to the assert function, which is expensive if this call is used in hot functions - we get lots of string concatenations.

Ideally, this would only take place when the assertion condition is false, which is when the string is logged out.

What are the options?

One I see is this:

// note that Debug.assert for this case is changed to simply unconditionally log args.
!assertion && Debug.assert(`Templated string with arguments ${argument}.`);

which works, but gives me this lint warning:

Is there something better?

[mvaligursky]

@willeastcott @slimbuck @kungfooman - thoughts?

[kungfooman]

Debug.assert(condition, () => `Templated string with arguments ${argument}.`);

Maybe like this? If given a function, we can just call/resolve it. The extra syntax of () => is a bit convoluted, but it could only be added in the hot path.

[mvaligursky]

@kungfooman - thanks! Yes, that was the first idea I looked at (and ChatGPT suggested), but it didn't feel clean enough, but perhaps it's fine. At the moment it feels a lot better than the suggestion I had in the initial post.

Any other ideas? If not, I'll go ahead with this I think.

[kungfooman]

We could also just remove the template string and make use of ...args?

I guess another caveat with !assertion && Debug.assert(...); would be the AST shaking (remnants in the ES5 compilate).

[slimbuck]

Yep agree with @kungfooman 👍🏻

[kungfooman]

Maybe:

Debug.assert(condition, 'Templated string with arguments', argument);

It's shorter, but it would still push more arguments on the stack every call... I didn't profile it, I just have a feeling () => would be faster, since the arrow function isn't usually called anyway 🤔