fix: check if route exist before checking Content-Type of body (#4286)

* check if route exist before checking content type

* added test for route check before content type

* pass tests

- check if the route is 404 only if the content-parser is undefined
by this we can avoid breaking changes.
- this also passes previous tests

this resolves issue
- fastify/fastify-multipart#381

* Update lib/contentTypeParser.js

Noted, thanks for the review

Co-authored-by: Manuel Spigolon <behemoth89@gmail.com>

* pass tests from wrong return

Co-authored-by: Manuel Spigolon <behemoth89@gmail.com>

lib/contentTypeParser.js

@@ -149,7 +149,11 @@ ContentTypeParser.prototype.run = function (contentType, handler, request, reply
   const resource = new AsyncResource('content-type-parser:run', request)
 
   if (parser === undefined) {
-    reply.send(new FST_ERR_CTP_INVALID_MEDIA_TYPE(contentType || undefined))
+    if (request.is404) {
+      handler(request, reply)
+    } else {
+      reply.send(new FST_ERR_CTP_INVALID_MEDIA_TYPE(contentType || undefined))
+    }
   } else if (parser.asString === true || parser.asBuffer === true) {
     rawBody(
       request,

test/404s.test.js

@@ -6,6 +6,7 @@ const fp = require('fastify-plugin')
 const sget = require('simple-get').concat
 const errors = require('http-errors')
 const split = require('split2')
+const FormData = require('form-data')
 const Fastify = require('..')
 
 function getUrl (app) {
@@ -18,7 +19,7 @@ function getUrl (app) {
 }
 
 test('default 404', t => {
-  t.plan(4)
+  t.plan(5)
 
   const test = t.test
   const fastify = Fastify()
@@ -74,6 +75,23 @@ test('default 404', t => {
         t.equal(response.headers['content-type'], 'application/json; charset=utf-8')
       })
     })
+
+    test('using post method and multipart/formdata', t => {
+      t.plan(3)
+      const form = FormData()
+      form.append('test-field', 'just some field')
+
+      sget({
+        method: 'POST',
+        url: getUrl(fastify) + '/notSupported',
+        body: form,
+        json: false
+      }, (err, response, body) => {
+        t.error(err)
+        t.equal(response.statusCode, 404)
+        t.equal(response.headers['content-type'], 'application/json; charset=utf-8')
+      })
+    })
   })
 })