[BUG] cause not populated in onFailure handler (event.data.error), no type for result property

[halfbakedsneed]

Describe the bug

After throwing a NonRetriableError with a cause property, In the object passed to onFailure:

• event.data.error.cause is not populated.
• result.cause is populated but the handler type does not surface result as a property that exists.

To Reproduce
Steps to reproduce the behavior:

1. Create a function with an onFailure handler:

const inngestFn = inngest.createFunction(
  {
    id: 'some-function',
    onFailure: async ({ event, env }) => {
      const eventData = event.data;

      const inputEvent = event.data.event;
      const inputEventData = inputEvent.data;

      const output = {
        expectedEventErrorCauseMessage: inputEventData.message,
        actualEventErrorCauseMessage: eventData.error.cause ?? null,
        // @ts-expect-error for some reason `result` is not in the type
        actualResultCauseMessage: eventData.result?.cause?.message,
      };

      return output;
    },
  },
  { event: 'app/some-event' },
  async ({ event, step }) => {
    throw new NonRetriableError('Some inngest error', {
      cause: { message: event.data.message }, // new Error(event.data.message) doesn't work either
    });
  },
);

2. Send this event:

{
  name: "app/some-event",
  data: {
    message: "some error message",
  },
},

3. Observe the output of the onFailure handler:

{
  "expectedEventErrorCauseMessage": "some error message",
  "actualEventErrorCauseMessage": null,
  "actualResultCauseMessage": "some error message"
}

MRE repository here

Expected behavior

In the above reproduction:

• actualEventErrorCauseMessage should equal some error message.
• Types should surface the result property in the object passed to the onFailure handler.

System info (please complete the following information):

• OS: MacOS Sonoma 14.4.1
• npm package Version 3.29.0
• Inngest CLI version 1.3.3
• Framework [e.g. Next.js, Express] N/A
• Platform [e.g. Vercel, AWS Lambda] Cloudflare Worker / Dev

[linear]

INN-4226 [BUG] `cause` not populated in `onFailure` handler (`event.data.error`), no type for `result` property