415 error on routes that does not exist with body multipart/form-data

[mage1k99]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the bug has not already been reported

Fastify version

4.0.0

Plugin version

7.1.0

Node.js version

v16.16.0

Operating system

macOS

Operating system version (i.e. 20.04, 11.3, 10)

12.5 (21G72)

Description

Fastify handles 404 for us, but when used with fastify multipart. it creates an 415 error instead of 404 for routes that does not exist. To demonstrate this I have created a project with fastify cli and tracked the steps to reproduce in each commits Link to repo.

I have tested a bunch of request with different method

Method	route	Shows 415 ?
GET	/notfound	false, 404 error thrown
POST	/notfound	true
PUT	/notfound	true
PATCH	/notfound	true
DELETE	/notfound	true

As you could see I'm getting 404 for a route that does not exist when using no body in POST request method

Now lets change the body type to multipart/form-data and send the request

This issue is the cause of issue #379 and created new issue as #379 (comment)

Steps to Reproduce

• create a project with fastify cli
• add the @fastify/multipart plugin
• register the multipart plugin by copy pasting the below code

import { FastifyMultipartAttactFieldsToBodyOptions } from "@fastify/multipart";
import fp from "fastify-plugin";

export interface RootPluginOptions {
  // Specify Support plugin options here
}

// The use of fastify-plugin is required to be able
// to export the decorators to the outer scope
export default fp<RootPluginOptions>(async (fastify, opts) => {
  fastify.register<FastifyMultipartAttactFieldsToBodyOptions>(
    require("@fastify/multipart"),
    {
      attachFieldsToBody: true,
    }
  );
});

• create route that accepts multipart/form-data in request
• send POST request with multipart/form-data as body to any route that does not exist. In our case I used /notfound route.
• the error is shown

Expected Behavior

• Throw 404 error instead of 415 error when a POST, PUT, PATCH, DELETE route that does not exist.
• This also creates confusion when development phase as the developer might get confused if the plugin got registred or not instead of checking the url

[mcollina]

Good spot! We should basically skip all the incoming body if it's a 404 request. This can be done by adding a few if checks in fastify-multipart using the req.is404 property (https://www.fastify.io/docs/latest/Reference/Request/).

Would you like to send a Pull Request to address this issue? Remember to add unit tests.

[mage1k99]

Sorry about the delay, the email notification did not work. will look at it as soon as possible

[mage1k99]

Hey @mcollina I don't think that this is the issue with fastify-multipart, this is issue with Should this be done in fastify itself ? This is because unregistered content type can cause 415 so checking if the route exist before checking the content type is registered is a good idea

As you could see at that 404 routes are handled by the default handler in onRequest

so adding request.is404 in ContentTypeParser.js Right here should do the job right ?

[mage1k99]

I have made a pull request, fastify/fastify#4286

[mcollina]

Good spot, thanks!