[BUG] 3.15.3 breaks union types returned from step.run

[gwax]

Describe the bug
Since 3.15.3, step.run with union return types are being given return type of Promise<any>

To Reproduce
Steps to reproduce the behavior:

1. Create file with:

import { EventSchemas, Inngest } from "inngest";

type Thing = {
  data: {
    stuff?: string | null;
  };
};

type Events = {
  "thing/thing": Thing;
};

const inngest = new Inngest({
  id: "inngest",
  schemas: new EventSchemas().fromRecord<Events>(),
});

function logstuff(stuff: string | null) {
  console.log(stuff);
}

export default inngest.createFunction(
  {
    id: "thing-thing",
  },
  { event: "thing/thing" },
  async ({ step, event }) => {
    let { stuff } = event.data;
    stuff = await step.run("fix-undefined-stuff", () => {  // <- this is typed as (...) => Promise<any> should be (...) => Promise<string | null>
      let newStuff = stuff;
      if (newStuff === undefined) {
        newStuff = null;
      }
      return newStuff;  // <- type = string | null
    });

    await step.run("log-stuff", () => {
      logstuff(stuff);  // <-- This line is fine on 3.15.2 but type errors on 3.15.3
    });
  },
);

2. Typecheck with inngest==3.15.2 -> no errors
3. Typeschek with inngest==3.15.3 -> type is not narrowed by running "fix-undefined-stuff" step

Expected behavior
No type errors

Code snippets / Logs / Screenshots

[{
	"resource": ".../thing.ts",
	"owner": "typescript",
	"code": "2345",
	"severity": 8,
	"message": "Argument of type 'string | null | undefined' is not assignable to parameter of type 'string | null'.\n  Type 'undefined' is not assignable to type 'string | null'.",
	"source": "ts",
	"startLineNumber": 38,
	"startColumn": 16,
	"endLineNumber": 38,
	"endColumn": 21
}]

System info (please complete the following information):

• OS: Mac
• npm package Version 3.15.4

Additional context
Add any other context about the problem here.

[linear]

INN-2857 [BUG] 3.15.4 breaks union types returned from step.run

[gwax]

Updated: the issue started in 3.15.3 NOT 3.15.4

[jpwilliams]

Thanks for the report, @gwax!

I've added a fix for this at #512. You can test it out now with:

npm install inngest@pr-512

Looks like our supported TS versions have grown wider than unional/type-plus that we've been using for the occasional helper type. The same happened recently with sindresorhus/type-fest in #500.

Let me know if the above works for you and I'll ship this tomorrow to fix.

[jpwilliams]

The above fix for this is shipped in v3.15.5. 🙂

[gwax]

I can confirm this is fixed. Thank you.