How can I publish an SDK that exports functions with "use workflow" and "use step"

[dylanjha]

At Mux we're working on some video-related workflows, and with that is coming an SDK that exports functions that can be thought of as "workflows" for example:

import { getSummaryAndTags } from '@mux/ai/workflows'

Right now, if you call that function it will do a few things in sequence:

• download sample frames from the video, the transcript, etc
• make a network request to an llm and get back a structured response
• etc.

The psuedo code inside the @mux/ai/workflows package is like this:

export async function getSummaryAndTags (assetId) {
  const images = await getImages(assetId);
  const transcript = await getTranscript(assetId);
  const summary = await getSummary(images, transcript);
  const tags = await getTags(images, transcript);
}

async function getImages (assetId) {
  // get images from Mux
}

async function getTranscript (assetId) {
  // get images from Mux
}

// .etc

I would LOVE to add use workflow / use step directives to the functions inside my SDK

export async function getSummaryAndTags (assetId) {
  'use workflow'
  const images = await getImages(assetId);
  const transcript = await getTranscript(assetId);
  const summary = await getSummary(images, transcript);
  const tags = await getTags(images, transcript);
}

async function getImages (assetId) {
   'use step'
  // get images from Mux
}

async function getTranscript (assetId) {
   'use step'
  // get images from Mux
}

// .etc

I think this makes a lot of sense (or someone tell me why this is a bad idea, I'd love to hear it):

• If someone is using this in a regular ol node or node-ish runtime, everything works the same, they can just call await getSummaryAndTags() the way they are doing today and everything is the same
• If someone is using WDK, they can do this:

import { start } from 'workflow/api';
import { getSummaryAndTags } from '@mux/ai/workflows'

await start(getSummaryAndTags, [assetId]);

⭐ and this would magically work ⭐ -- no extra configuration or setup required and now the workflows

The blocker

However, I'm testing this out with a locally built and locally linked package and it's not working. I can see in the node_modules/ that the directives are in the functions, but it ends up with an error:

Error [WorkflowRuntimeError]: 'start' received an invalid workflow function. Ensure the Workflow Development Kit is configured correctly and the function includes a 'use workflow' directive.

Questions

Can anyone figure out why this is not working?

I have a hunch that the WDK sort of "scans" for the "use workflow" / "use step" directives in the dev server or at build time, and it's only scanning application-level code, and it's not looking at the code that gets imported from dependencies?

Is something like that going on?

Is this considered a bug? What is the desired behavior?

[pranaygp]

@dylanjha this definitely should be supported in workflow, and having "use workflow" and "use step" in published npm packages the way you described is an intentional design decision of workflow:

• If someone is using this in a regular ol node or node-ish runtime, everything works the same, they can just call await getSummaryAndTags() the way they are doing today and everything is the same
• If someone is using WDK, they can do this:

import { start } from 'workflow/api';
import { getSummaryAndTags } from '@mux/ai/workflows'

await start(getSummaryAndTags, [assetId]);

⭐ and this would magically work ⭐ -- no extra configuration or setup required and now the workflows

Will try to repro and make sure this actually works including in dev and prod builds. I'm not surprised if there is a bug in our current bundling for this