why does requiring stack outputs return an `Output lt T gt `

Question

why does requiring stack outputs return an `Output lt T gt ` instead of just `T` or `Promise lt T gt ` stack outputs will be known at preview time but since they return `Output lt T gt ` i can t use those values until deploy time

red-match-15116 · Answer

Output lt T gt is essentially like Promise lt T gt Except that instead of ` then ` you have to use ` apply ` to access the unwrapped value

breezy-butcher-78604 · Answer

yeah i know but the output of an `apply` is another `Output lt T gt ` whereas with a promise I can `await` it and access the underlying value at preview time

red-match-15116 · Answer

You can still access the value of Output at preview time if the value is known

red-match-15116 · Answer

You just have to do it within the apply

red-match-15116 · Answer

Is there something that isn t doing what you expect

breezy-butcher-78604 · Answer

let me throw together some example code

little-cartoon-10569 · Answer

I don t think you can guarantee that stack outputs will be known at preview time It wouldn t be safe to assume that the outputting stack is not currently being deployed

little-cartoon-10569 · Answer

Or even that the stack is local on your machine You could and frequently are getting those outputs from a stack at <http api pulumi com|api pulumi com> or S3 These have the same async requirements as deploying to a remote API or S3

breezy-butcher-78604 · Answer

yeah that makes sense but wouldn t that same issue occur at deploy time too ie if I m deploying a resource in `Stack A` using a stack output from `Stack B` what happens if `Stack B` is deploying while `Stack A` is using that output

breezy-butcher-78604 · Answer

how does `requireOutput ` behave in that scenario

little-cartoon-10569 · Answer

I for one am happy to trust our new Pulumi overlords that it ll be alright once Pulumi looks after resolving dependencies