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Some context: I'd like to deploy a full-stack app with Pulumi and I need to do the following: 1. Deploy backend (dynamoDB + API Gateway) 2. Build the frontend locally using the API URL from step 1 3. Deploy frontend (S3+Cloudfront) In order to do step 2 I created a custom Resource and Resource provider that gets the API URL as input, builds the frontend locally using yarn and outputs the local path of the static assets. I want to pass this output (

yarnBuild.path

) as an input to the BucketObject

You're close. I think you want something like

pulumi
    .all([yarnBuild.path])
    .apply(([p]) => new aws.s3.BucketObject("index.html", {
        acl: "public-read",
        contentType: "text/html",
        bucket: bucket,
        source: new pulumi.asset.FileAsset(`${p}/index.html`)
    }));

Worth noting that .apply(...) documentation says not to declare new resources within an apply

Yes, the best practice is that you don't. If you do, you might find that the resources created there don't show up in the preview

Hi @brave-planet-10645 I just tried your solution but the preview fails with:

error: Error: failed to register new resource index.html [aws:s3/bucketObject:BucketObject]: 2 UNKNOWN: failed to compute asset hash: failed to open asset file 'undefined/index.html': open undefined/index.html: no such file or directory

Then I tried to run with:

pulumi
    .all([yarnBuild.path])
    .apply(([p]) => p && new aws.s3.BucketObject("index.html", {
        acl: "public-read",
        contentType: "text/html",
        bucket: bucket,
        source: new pulumi.asset.FileAsset(`${p}/index.html`)
    }));

Now the deploy works but it doesn't create the BucketObject (after the deploy, there's an empty S3 bucket)

That's probably because you've got the

p && new...

in there. I'm not sure that this would work. Where are you getting yarnBuild.path from?

if I don't put

p && new...

the preview fails as p is undefined. yarnBuild is a custom dynamic provider:

export interface YarnResourceInputs {
    apiUrl: pulumi.Input<string>;
}
interface YarnResourceProviderInputs {
    apiUrl: string;
}
interface YarnResourceProviderOutputs {
    path: string;
}

const YarnResourceProvider: pulumi.dynamic.ResourceProvider = {
    async create(inputs: YarnResourceProviderInputs): Promise<pulumi.dynamic.CreateResult> {
       //build frontend with "yarn build"
 console.log('YarnResourceProvider:create ', inputs.apiUrl)
        return { id: "123", outs: { path: './dist' }};
    },
    async diff(id: string, olds: YarnResourceProviderInputs, news: YarnResourceProviderInputs): Promise<pulumi.dynamic.DiffResult> {
        return {changes: true, replaces: ['apiUrl']}
    }
}

class YarnResource extends pulumi.dynamic.Resource {
    public readonly path!: pulumi.Output<string>;
    constructor(name: string, props: YarnResourceInputs, opts?: pulumi.CustomResourceOptions) {
        super(YarnResourceProvider, name, props, opts);
    }
}

I don't understand why we would do

pulumi.all(...)

for a single output since that is meant to be used to get multiple outputs into the same apply delegate. Why not just

yarnBuild.path.apply(p => new aws.s3.BucketObject(...));

Also it doesn't look like

YarnResource

is setting and/or registering

path

as an output?

So I think you're both wrong ( 😉 )... this is a dynamic resource which I don't think uses outputs... so Joshua: outputs don't need to be registered and Eric: you don't need to use outputs here

Gotcha - Haven't had the chance to use dynamic resources yet 🙂

@bored-oyster-3147 I tried

yarnBuild.path.apply(...)

but it fails in the preview run as

yarnBuild.path == undefined

Well that's because you're not setting it, right?

yes, in the

YarnResourceProvider

create function

but I don't think that sets

YarnResource.path

. You need to set it in your

YarnResource

constructor after calling the base constructor. And @brave-planet-10645 is saying that it can be

string

instead of

Output<string>

@brave-planet-10645 I don't get why you say I don't need outputs here. The

YarnResourceProvider

is supposed to run "yarn build", grab the path of the build and return it as an output to be used by the bucket resource

Does it actually convert the string into an

Output<string>

?

so far I'm just mocking it with:

async create(inputs: YarnResourceProviderInputs): Promise<pulumi.dynamic.CreateResult> {
       //build frontend with "yarn build"
        return { id: "123", outs: { path: './dist' }};
    },

I'm using examples from your docs. Do I need to convert the

'./dist'

part to an output object? I thought Pulumi did this automatically

I would expect Pulumi to do that automatically. I'll have a play with resource providers tomorrow morning and see what I can find out. This looks like we need some better examples in the examples repo as well

Ok I just scanned the docs for this and you're right about not needing to set that property explicitly, I'm sorry. There is some magic happening to set that from your

CreateResult

. Not a fan of magic implementations like that but my bad for confusing the discussion I did notice that your code differs from the documentation example slightly on 1 point:

...

interface MyResourceProviderOutputs {
    myNumberOutput: number;
    myStringOutput: string;
}

class MyResourceProvider implements pulumi.dynamic.ResourceProvider {
    async create(inputs: MyResourceProviderInputs): Promise<pulumi.dynamic.CreateResult> {
        ...
        // Values are for an example only.
        return { id: "...", outs: { myNumberOutput: 12, myStringOutput: "some value" }};
    }
}

export class MyResource extends pulumi.dynamic.Resource {
    public readonly myStringOutput!: pulumi.Output<string>;
    public readonly myNumberOutput!: pulumi.Output<number>;

    constructor(name: string, props: MyResourceInputs, opts?: pulumi.CustomResourceOptions) {
        super(myprovider, name, { myStringOutput: undefined, myNumberOutput: undefined, ...props }, opts);
    }
}

Maybe that object expansion in the

super

call is important? They are doing something similar in all of the other SDK examples. Maybe your

super

call should be

super(YarnResourceProvider, name, { path: undefined, ...props }, opts);

Hi @bored-oyster-3147 I don't think that makes any difference

Weird to be in the documentation then. Why would they use object expansion to add null output properties to the input obj? very weird

So I've taken a look, and I think Joshua is correct here. You do need to expand the object. So using Eric's original code and adding the expanded object:

import * as pulumi from "@pulumi/pulumi";

export interface YarnResourceInputs {
    apiUrl: pulumi.Input<string>;
}
interface YarnResourceProviderInputs {
    apiUrl: string;
}
interface YarnResourceProviderOutputs {
    path: string;
}
const YarnResourceProvider: pulumi.dynamic.ResourceProvider = {
    async create(inputs: YarnResourceProviderInputs): Promise<pulumi.dynamic.CreateResult> {
       //build frontend with "yarn build"
//  console.log('YarnResourceProvider:create ', inputs.apiUrl)
        return { id: "123", outs: { path: './dist' }};
    },
    async diff(id: string, olds: YarnResourceProviderInputs, news: YarnResourceProviderInputs): Promise<pulumi.dynamic.DiffResult> {
        return {changes: true, replaces: ['apiUrl']}
    }
}
export class YarnResource extends pulumi.dynamic.Resource {
    public readonly path!: pulumi.Output<string>;
    constructor(name: string, props: YarnResourceInputs, opts?: pulumi.CustomResourceOptions) {
        super(YarnResourceProvider, name, {path: undefined, ...props}, opts);
    }
}

And then updating the program slightly so the bucketobject isn't created in the apply, but the fileasset, you get something like this:

import * as pulumi from "@pulumi/pulumi";
import * as provider from "./provider";
import * as aws from "@pulumi/aws";

const yarn = new provider.YarnResource("yarn", {
    apiUrl: "<http://thing.com|thing.com>"
});

export const path = yarn.path;

const bucket = new aws.s3.Bucket("bucket");

const file = yarn.path.apply(x => new pulumi.asset.FileAsset(x));

const bucketObject = new aws.s3.BucketObject("object", {
    source: file,
    bucket
})

Thanks @brave-planet-10645! That worked 😃