fix: incorrect error types (#222)

* fix: incorrect error types

* add tsd assertions

Author: ddadaal

index.d.ts

@@ -1,7 +1,7 @@
 import * as busboy from "busboy";
 import { FastifyPlugin } from "fastify";
 import { Readable } from 'stream';
-import { FastifyError } from "fastify-error";
+import { FastifyErrorConstructor } from "fastify-error";
 
 type MultipartHandler = (
     field: string,
@@ -41,12 +41,12 @@ interface MultipartValue<T> {
 }
 
 interface MultipartErrors {
-    PartsLimitError: FastifyError,
-    FilesLimitError: FastifyError,
-    FieldsLimitError: FastifyError,
-    PrototypeViolationError: FastifyError,
-    InvalidMultipartContentTypeError: FastifyError,
-    RequestFileTooLargeError: FastifyError
+    PartsLimitError: FastifyErrorConstructor,
+    FilesLimitError: FastifyErrorConstructor,
+    FieldsLimitError: FastifyErrorConstructor,
+    PrototypeViolationError: FastifyErrorConstructor,
+    InvalidMultipartContentTypeError: FastifyErrorConstructor,
+    RequestFileTooLargeError: FastifyErrorConstructor
 }
 
 declare module "fastify" {

test/index.test-d.ts

@@ -5,6 +5,7 @@ import * as util from 'util'
 import { pipeline } from 'stream'
 import * as fs from 'fs'
 import { expectError, expectType } from 'tsd'
+import { FastifyErrorConstructor } from "fastify-error"
 
 const pump = util.promisify(pipeline)
 
@@ -141,6 +142,21 @@ const runServer = async () => {
   // access all errors
   app.post('/upload/files', async function (req, reply) {
     const { FilesLimitError } = app.multipartErrors
+
+    expectType<FastifyErrorConstructor>(app.multipartErrors.FieldsLimitError);
+    expectType<FastifyErrorConstructor>(app.multipartErrors.FilesLimitError);
+    expectType<FastifyErrorConstructor>(app.multipartErrors.InvalidMultipartContentTypeError);
+    expectType<FastifyErrorConstructor>(app.multipartErrors.PartsLimitError);
+    expectType<FastifyErrorConstructor>(app.multipartErrors.PrototypeViolationError);
+    expectType<FastifyErrorConstructor>(app.multipartErrors.RequestFileTooLargeError);
+
+    // test instanceof Error
+    const a = new FilesLimitError();
+    if (a instanceof FilesLimitError) {
+      console.log("FilesLimitError occurred.");
+    }
+
+    reply.send();
   })
 
   await app.ready()