fix: Allow local options to override signing key

[salmanm]

Just added a test case to demonstrate a problem I've noticed. I'm a bit surprised to see this not working which made me think whether I'm expecting correct behaviour! 😅

Basically I can not override signing key/secret in the reply.jwtSign

Please could someone validate if the test case I've added is the expected one? I'll update the code then.

Thanks

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[jmjf]

TL:DR; Use a namespace.

  const fastify = Fastify()
  fastify.register(jwt, options)
  fastify.register(jwt, { ...options, secret: 'something-else', namespace: 'refresh' });

  fastify.post('/sign', async function (request, reply) {
    const { token, refreshToken } = request.body
    const refreshTokenSigned = await reply.refreshJwtSign(refreshToken) // signing by different key
    const tokenSigned = await reply.jwtSign(token)
    return reply.send({ tokenSigned, refreshTokenSigned })
  })

Before I came to that answer, I did some digging in the debugger. Details below in case you're interested.

At

fastify-jwt/jwt.js

Line 389 in f6e079e

const signerOptions = mergeOptionsWithKey(options.sign || options, secretOrPrivateKey)

options (from replySign scope) = { key: 'something-else' }
secretOrPrivateKey (from fastifyJwt scope) = 'test'

When this line executes, signerOptions is set to { key: 'test' }.

mergeOptionsWithKey at L269-L276
gets parameter values options = { key: 'something-else' }, useProvidedPrivateKey = 'test'. So it takes take the first branch and test becomes the key.

I experimented a bit trying to find a way to make it work, but broke other tests every time.

requestVerify at

fastify-jwt/jwt.js

Line 491 in f6e079e

const verifierOptions = mergeOptionsWithKey(options.verify || options, secretOrPublicKey)

is doing the same thing, so it seems that the intended behavior is that you can't override the key in reply.jwtSign or request.jwtVerify by passing options.

But, as noted above, you can use a namespace and use the namespaced decorators. (Today was a good day because I learned something.)