Hi folks is there any chance someone could take another look Pulumi Community #typescript

Hi folks, is there any chance someone could take a...

dazzling-oxygen-84405

09/29/2024, 12:31 PM

Hi folks, is there any chance someone could take another look at this issue? I've just tripped over it again, and the previous PR seems abandoned. tl;dr -

pulumi.output

doesn't work on classes, e.g. in

pulumi.output(new URL()).apply(url => ...)

inside the apply,

url

is no longer an instance of

URL

, but just a plain object.

little-cartoon-10569

09/29/2024, 7:23 PM

You know in JS/TS, classes aren't first-class objects? They're erased at transpile time. Nothing is an instance of a class at runtime. You can use types for this sort of thing, if you want. But not classes.

dazzling-oxygen-84405

09/29/2024, 7:28 PM

This is TS, yeah. The PR linked to that issue proposed just checking whether the object has a prototype, and if it does, assuming it is a custom class, which seems sensible? Like this:

Copy code

if (Object.getPrototypeOf(x) == Object.prototype) {
  // Is a plain-old-object, recurse into values (existing logic)
} else {
  // Is a custom class, don't recurse (new)
}

little-cartoon-10569

09/29/2024, 7:35 PM

Not sure. I generally just check for the important properties. There's also a way to check if all the keys of one object are in another, right? It's not a problem I've solved much, sorry.

little-cartoon-10569

09/29/2024, 7:38 PM

Maybe for your example,

Object.getPrototypeOf(url) == (new URL()).prototype

would be the right check?

little-cartoon-10569

09/29/2024, 7:38 PM

Or URL.prototype? I don't know.

dazzling-oxygen-84405

09/29/2024, 7:41 PM

Yes, the point of the issue is that this check should happen in the

pulumi.output

function, not my code. I expect to be able to do this:

Copy code

function foo(x: pulumi.Input<URL>) {
  pulumi.output(x).apply(url => /* use url as an instance of URL() here */ )
}

and it currently doesn't work.

dazzling-oxygen-84405

09/29/2024, 7:42 PM

Inside the

.apply()

url

is a plain old object, not an instance of

URL

. Because

pulumi.output

strips the prototype information. I don't think this is intentional, hence the bug report.

little-cartoon-10569

09/29/2024, 7:45 PM

Yea, it's awkward. Generics, classes and runtime don't mix in Typescript. I don't think it's a bug though. I think it's a limitation. If the class of the output is defined in your code, how could Pulumi put it back in, within its code?

dazzling-oxygen-84405

09/29/2024, 7:56 PM

This isn't specific to Typescript, the bug exists in JS as well. If I have an instance of a class (i.e. the object's

prototype

is the class definition), then pulumi shouldn't try to recursively unwrap it, and just treat it as opaque.

dazzling-oxygen-84405

09/29/2024, 7:57 PM

Like is done in this proposed PR, it's not clear why it was closed: https://github.com/pulumi/pulumi/pull/13567

little-cartoon-10569

09/29/2024, 7:57 PM

Ah. Right. If that's what happening, then something can be done about that.

little-cartoon-10569

09/29/2024, 8:02 PM

The test in that PR doesn't prove that it will solve your problem though. Might need another test for type checking. Also, what happens if the class contains wrapped properties? Wouldn't we want them unwrapped? 🤔 Maybe not? If

new MyResource().nestedResource

is an

Output<MyComponentResource>

then I guess we wouldn't want it unwrapped. Tough one.

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