Getting Promise Rejection Error for Fastify | NestJS | Page 1

zenith wing Oct 29, 2022, 3:42 PM

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Hi guys,

im facing the following error on my production system:

<rejected> TypeError: Cannot read property 'preSerialization' of undefined
at preserializeHook (/node_modules/fastify/lib/reply.js:461:28)
at Reply.send (/node_modules/fastify/lib/reply.js:190:7)
at FastifyAdapter.reply (/node_modules/@nestjs/platform-fastify/adapters/fastify-adapter.js:167:29)
at ExceptionsHandler.catch (/node_modules/@nestjs/core/exceptions/base-exception-filter.js:28:28)
at ExceptionsHandler.next (/node_modules/@nestjs/core/exceptions/exceptions-handler.js:16:20)
at /node_modules/@nestjs/core/router/router-proxy.js:13:35
} reason: TypeError: Cannot read property 'preSerialization' of undefined
at preserializeHook (/node_modules/fastify/lib/reply.js:461:28)
at Reply.send (/node_modules/fastify/lib/reply.js:190:7)
at FastifyAdapter.reply (/node_modules/@nestjs/platform-fastify/adapters/fastify-adapter.js:167:29)
at ExceptionsHandler.catch (/node_modules/@nestjs/core/exceptions/base-exception-filter.js:28:28)
at ExceptionsHandler.next (/node_modules/@nestjs/core/exceptions/exceptions-handler.js:16:20)
at /node_modules/@nestjs/core/router/router-proxy.js:13:35```

I tried catching it and logging the stack trace but it always defaults to this error message. I'm seriously lost here, can anybody point me in the right direction?

violet swift Oct 29, 2022, 3:43 PM

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Can you replicate this locally, or is it only in production?

zenith wing Oct 29, 2022, 3:44 PM

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Only in production, when i spin up my local environment and do the same API request with the same body nothing happens

violet swift Oct 29, 2022, 3:44 PM

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Hmm, that's gonna make debugging this difficult

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All endings or just a specific one?

zenith wing Oct 29, 2022, 3:45 PM

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That's why I'm asking if anyone has ideas 😄

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Just a specific endpoint

violet swift Oct 29, 2022, 3:45 PM

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Hmm. Can you share that endpoint's code?

zenith wing Oct 29, 2022, 3:46 PM

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Not really unfortunately. It's a) much happening there in case of events and db and b) bound by NDA

violet swift Oct 29, 2022, 3:46 PM

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Yeah it's more of just wanting to check for all promises going on, but I get it

zenith wing Oct 29, 2022, 3:47 PM

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I tried this

        console.log('Unhandled Rejection at: Promise', p, 'reason:', error);
        console.dir(error.stack);
        // application specific logging, throwing an error, or other logic here
    });```

but it's still the same error. SO pointed me to that to see the underlying promise that is failing but no change in output

violet swift Oct 29, 2022, 3:48 PM

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It looks like from the stack trace the way Reply is created/used is incorrect in the adapter. The_only_ way I could see that happening is if somehow you possibly have different fastify versions

zenith wing Oct 29, 2022, 3:49 PM

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i indeed have to fastifys in my package.json but i dont know why

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        "@nestjs/platform-fastify": "^9.1.4",```

violet swift Oct 29, 2022, 3:50 PM

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@fastify/static is a plugin for fastify. @nestjs/platform-fastify is the http adapter package to make nest work with fastify. Neither of them are fastify itself

zenith wing Oct 29, 2022, 3:51 PM

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        "fastify-multipart": "^5.4.0",```

these two are for image handling

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no more fastify packages in package.json

violet swift Oct 29, 2022, 3:51 PM

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Is this an endpoint that is handling multipart data?

zenith wing Oct 29, 2022, 3:52 PM

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No

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It's an endpoint for sending out an email

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But it fails even before we get to the sending

violet swift Oct 29, 2022, 4:11 PM

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It's weird that this looks like a double rejected promise too. I've not seen something like this before

zenith wing Oct 29, 2022, 4:11 PM

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why double?

violet swift Oct 29, 2022, 4:12 PM

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Unhandled Refection at: Promise Promise { stack trace } stack trace

zenith wing Oct 29, 2022, 4:12 PM

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zenith wing I tried this ``` process.on('unhandledRejection', (error: Error, p) => { ...

Thats because of this

violet swift Oct 29, 2022, 4:13 PM

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Ah, okay.

zenith wing Oct 29, 2022, 4:13 PM

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Do you know that this preSerialization hook does anyways?

violet swift Oct 29, 2022, 4:13 PM

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Based on the name, gets the response ready to be serialized. Do I actually know? No

zenith wing Oct 29, 2022, 4:15 PM

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😄

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Can this be a frontend error when a wrong content-type is selected?

violet swift Oct 29, 2022, 4:16 PM

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Possibly? Most of the time it's just a JSON response

zenith wing Oct 30, 2022, 4:54 PM

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so we tried with application/json from the frontend as well and it put out the same error

violet swift Oct 30, 2022, 4:57 PM

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That's super weird. I'd need some code that reproduces that to possibly get a better understanding of what's going on

zenith wing Oct 30, 2022, 5:26 PM

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WE FOUND IT

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omg

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The frontend send the authorization header like this: "Bearer " because the accesstoken was null on the frontend because it was not needed for the api

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fastify fails there

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when bearer is send with empty token

#Getting Promise Rejection Error for Fastify