Complex pulumi.Ouputs; using apply when an output string is constructed from multiple places in an iac code base

[gmhta]

File: content/docs/iac/concepts/inputs-outputs/apply.md

Issue

The is not clear documentation on how to construct an complex Output<string> when there contents comes from multiple places in the code base.

Suggestion

Add a section to the apply.md doc, specifically dealing with this pattern.

Example text

Solutions in typescript only.

Solution 1.
Context
A complex output is being constructed in multiple places in the code base.
And the place that is collecting the output can't be changes (e.g. BootScript class is provided by a thirdparty)

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

const r1 = new random.RandomString("random1", {
    length: 16,
});
const r2 = new random.RandomString("random2", {
  length: 16,
});

class BootScript {
  lines: string[] = [];

  sh(line: string) {
    this.lines.push(line);
  }

  compile(): string {
    return this.lines.join("\n")
  }
}

const bs0 = new BootScript()

const bs1 = r1.result.apply(v => {
  bs0.sh(`R1=${v}`)
  return bs0
})

/// Note, the following doesn't work, as bs is of type pulumi.UnwrappedObject<BootScript>, and not BootScript
// pulumi.all([bs1, r2.result]).apply(([bs, v]) => { bs.sh(`R2=${v}`); return bs } )
const bs2 = bs1.apply(bs => {
  return r2.result.apply(v => {
    bs.sh(`R2=${v}`)
    return bs
  })
})

export const data = bs2.apply(v => v.compile())

Solution 2.
Context
A complex output is being constructed in multiple places in the code base.
And the place that is collecting the output CAN be changes

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

const r1 = new random.RandomString("random1", {
  length: 16,
});
const r2 = new random.RandomString("random2", {
  length: 16,
});

class BootScript {
  lines: pulumi.Output<string>[] = [];

  sh(line: string): void;
  sh(line: pulumi.Output<string>): void;
  sh(line: pulumi.Output<string> | string): void {
    switch (typeof line) {
      case "string":
        this.lines.push(pulumi.output(line));
        break
      case "object":
        this.lines.push(line);
        break
    }
  }

  compile(): pulumi.Output<string> {
    // could used all instead of output
    return pulumi.output(this.lines).apply(v => v.join("\n"))
  }
}

const bs = new BootScript()

bs.sh("#!/bin/sh")
// apply or interpolate
bs.sh(r1.result.apply(v => `R1=${v}`))
bs.sh(pulumi.interpolate`R2=${r2.result}`)

export const data = bs.compile()

[shughes26]

Thanks for your feedback! We'll look into this while we seek to continuously improve our docs.