move createError-calls out of function (#405)

index.js

@@ -20,6 +20,14 @@ const kMultipart = Symbol('multipart')
 const kMultipartHandler = Symbol('multipartHandler')
 const getDescriptor = Object.getOwnPropertyDescriptor
 
+const PartsLimitError = createError('FST_PARTS_LIMIT', 'reach parts limit', 413)
+const FilesLimitError = createError('FST_FILES_LIMIT', 'reach files limit', 413)
+const FieldsLimitError = createError('FST_FIELDS_LIMIT', 'reach fields limit', 413)
+const RequestFileTooLargeError = createError('FST_REQ_FILE_TOO_LARGE', 'request file too large, please check multipart config', 413)
+const PrototypeViolationError = createError('FST_PROTO_VIOLATION', 'prototype property is not allowed as field name', 400)
+const InvalidMultipartContentTypeError = createError('FST_INVALID_MULTIPART_CONTENT_TYPE', 'the request is not multipart', 406)
+const InvalidJSONFieldError = createError('FST_INVALID_JSON_FIELD_ERROR', 'a request field is not a valid JSON as declared by its Content-Type', 406)
+
 function setMultipart (req, payload, done) {
   // nothing to do, it will be done by the Request.multipart object
   req.raw[kMultipart] = true
@@ -173,14 +181,6 @@ function fastifyMultipart (fastify, options, done) {
     ? options.throwFileSizeLimit
     : true
 
-  const PartsLimitError = createError('FST_PARTS_LIMIT', 'reach parts limit', 413)
-  const FilesLimitError = createError('FST_FILES_LIMIT', 'reach files limit', 413)
-  const FieldsLimitError = createError('FST_FIELDS_LIMIT', 'reach fields limit', 413)
-  const RequestFileTooLargeError = createError('FST_REQ_FILE_TOO_LARGE', 'request file too large, please check multipart config', 413)
-  const PrototypeViolationError = createError('FST_PROTO_VIOLATION', 'prototype property is not allowed as field name', 400)
-  const InvalidMultipartContentTypeError = createError('FST_INVALID_MULTIPART_CONTENT_TYPE', 'the request is not multipart', 406)
-  const InvalidJSONFieldError = createError('FST_INVALID_JSON_FIELD_ERROR', 'a request field is not a valid JSON as declared by its Content-Type', 406)
-
   fastify.decorate('multipartErrors', {
     PartsLimitError,
     FilesLimitError,