Fix redirect reponseAsJson

[firede]

Issue

const res = await fetch("/api/auth/signin/email", {
  method: "post",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({ ...values, json: true /* NOTE */ }),
})
console.log(res)

NOTE

• json: true triggers a 302 redirect
• json: "true" reponse as JSON

Expected

• json: true reponse as JSON

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[iaincollins]

Thanks for the submission!

The current behaviour is correct as the form is application/x-www-form-urlencoded rather than anticipating JSON because it supports clients that do not have JavaScript enabled.

We could introduce the option to support JSON as well, but there would need to be quite a bit of regression testing, because there are other parts of the flow that would break, as the expected submission is currently always application/x-www-form-urlencoded.

The easiest way to submit a sign in form, is with the sign in client method, which handles both form encoding and CSRF token submission.

import { signIn } from 'next-auth/client'

export default ({ email }) => (
  <button onClick={() => signIn('email', { email })}>Sign in with Email</button>
)

[firede]

@iaincollins Thanks for the explanation!

Related case: #541

I am try to implement it on the same page:

1. Send verification email
2. Paste verification code
3. Verify and login

The signIn API will redirect to the verification request page by default, which cannot satisfy the above interaction.
Do you have any suggestions?