Invalid handler. It should be a function

[edimitchel]

Environment

h3 1.8.0-rc.2 and 1.8.0-rc.3
OSX, with pnpm 8.6

Reproduction

https://stackblitz.com/edit/github-uqdf6b?file=package.json

Describe the bug

The issue occurred when I tried to illustrate a feature request.

When I use listhen since h3 was added with the rc version (the 2nd), I got this following issue:

ERROR Invalid handler. It should be a function:

Code:

app.use(
  '/api',
  eventHandler((event) =>
    proxyRequest(event, join(BACKEND_ENDPOINT, event.path))
  )
);

Additional context

According to the error message, it is linked with fromNodeMiddleware.

Here the trace from the function (in h3):

    at fromNodeMiddleware (file:///Users/micheledighofffer/DEV/listhen/node_modules/.pnpm/h3@1.8.0-rc.3/node_modules/h3/dist/index.mjs:1840:31)
    at loadHandle (file:///Users/micheledighofffer/DEV/listhen/dist/index.mjs:892:26)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async listenAndWatch (file:///Users/micheledighofffer/DEV/listhen/dist/index.mjs:998:3)
    at async Object.run (file:///Users/micheledighofffer/DEV/listhen/dist/cli.mjs:91:7)
    at async runCommand (file:///Users/micheledighofffer/DEV/listhen/node_modules/.pnpm/citty@0.1.2/node_modules/citty/dist/index.mjs:313:5)
    at async runMain (file:///Users/micheledighofffer/DEV/listhen/node_modules/.pnpm/citty@0.1.2/node_modules/citty/dist/index.mjs:425:7)

The function is called by listhen even it's not use in the app.

It seems that the type is not the one expected and doesn't match the change made by @danielroe (7e9570)
The handler type is not function but object.

Logs

No response

[danielroe]

The issue is that you have not exported a handler function from your app.ts file. Add the following line at the end and you should be fine: export default app

[edimitchel]

Thank you,
Isn't possible to add an hint in console to prevent that kind of issue?

[pi0]

Transfered to listhen to improve error

[pi0]

better error in the next version: