ERROR: Cannot set headers after they are sent to the client : Cannot set headers after they are sent to the client about h3 HOT 8 CLOSED

Thank you for reply, @danielroe !
I'll make repo without Nuxt.

Here you are. https://github.com/ChangJoo-Park/h3-issue-21/

It is not happen. It seems to have occurred because of h3 with Nuxt.

I met this error https://github.com/ChangJoo-Park/nuxt-without-nitro-demo/blob/65786ca495f8a24939451923ddaa0f7ebf54f125/server/hello.js#L1-L8 . Using h3 with Nuxt

from h3.

Also getting this error systematically when trying to implement server-sent events in a fresh Nuxt3 project.

from h3.

This issue caused by ky-universal in nuxt/http module. not h3's fault.

from h3.

Reopen, It failed with axios with h3. but axios with express deploy success on vercel.
Here is full error logs.

2021-03-16T12:30:43.457Z	65954691-80e8-4140-ab8c-c93745ae5689	ERROR	Unhandled Promise Rejection 	{"errorType":"Runtime.UnhandledPromiseRejection","errorMessage":"Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client","reason":{"errorType":"Error","errorMessage":"Cannot set headers after they are sent to the client","code":"ERR_HTTP_HEADERS_SENT","stack":["Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client","    at ServerResponse.setHeader (_http_outgoing.js:558:11)","    at sendError (/var/task/node_modules/h3/dist/index.js:502:7)","    at /var/task/node_modules/h3/dist/index.js:514:14"]},"promise":{},"stack":["Runtime.UnhandledPromiseRejection: Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client","    at process.<anonymous> (/var/runtime/index.js:35:15)","    at process.emit (events.js:327:22)","    at processEmit [as emit] (/var/task/node_modules/signal-exit/index.js:161:32)","    at processPromiseRejections (internal/process/promises.js:245:33)","    at processTicksAndRejections (internal/process/task_queues.js:94:32)"]}
Unknown application error occurred

from h3.

@ChangJoo-Park Thank you so much for your contributions - PRs and issues! ❤️

Could you create a reproduction without Nuxt? (Or alternatively, raise this as an issue in the nuxt repo if it's specific to Nuxt?)

from h3.

Same issue as well

from h3.

Just started getting his error too. Fresh project.

ERROR [unhandledRejection] Cannot set headers after they are sent to the client 21:36:35

at new NodeError (node:internal/errors:372:5)
at ServerResponse.setHeader (node:_http_outgoing:576:11)
at sendError (/C:/Users/tobychidi/Documents/GitHub/CodeKing/codeking-nuxt/node_modules/.pnpm/[email protected]/node_modules/h3/dist/index.mjs:233:13)
at nodeHandler (/C:/Users/tobychidi/Documents/GitHub/CodeKing/codeking-nuxt/node_modules/.pnpm/[email protected]/node_modules/h3/dist/index.mjs:396:15)

from h3.

There might be several usage issues that call a utility from h3 after headers are sent. If you think it might be a bug with h3, please share a reproduction 🙏🏼

from h3.