do not use a default upload protocol

packages/@uppy/companion/src/server/Uploader.js

@@ -93,9 +93,8 @@ function validateOptions (options) {
   }
 
   // validate protocol
-  // @todo this validation should not be conditional once the protocol field is mandatory
-  if (options.protocol && !Object.keys(PROTOCOLS).some((key) => PROTOCOLS[key] === options.protocol)) {
-    throw new ValidationError('unsupported protocol specified')
+  if (options.protocol == null || !Object.keys(PROTOCOLS).some((key) => PROTOCOLS[key] === options.protocol)) {
+    throw new ValidationError('please specify a valid protocol')
   }
 
   // s3 uploads don't require upload destination
@@ -208,8 +207,7 @@ class Uploader {
   }
 
   async _uploadByProtocol () {
-    // @todo a default protocol should not be set. We should ensure that the user specifies their protocol.
-    const protocol = this.options.protocol || PROTOCOLS.multipart
+    const { protocol } = this.options
 
     switch (protocol) {
       case PROTOCOLS.multipart:

packages/@uppy/companion/test/__tests__/companion.js

@@ -36,7 +36,7 @@ describe('validate upload data', () => {
         protocol: 'tusInvalid',
       })
       .expect(400)
-      .then((res) => expect(res.body.message).toBe('unsupported protocol specified'))
+      .then((res) => expect(res.body.message).toBe('please specify a valid protocol'))
   })
 
   test('invalid upload fieldname gets rejected', () => {

packages/@uppy/companion/test/__tests__/uploader.js

@@ -20,10 +20,13 @@ process.env.COMPANION_DATADIR = './test/output'
 process.env.COMPANION_DOMAIN = 'localhost:3020'
 const { companionOptions } = standalone()
 
+const protocol = 'tus'
+
 describe('uploader with tus protocol', () => {
   test('uploader respects uploadUrls', async () => {
     const opts = {
       endpoint: 'http://localhost/files',
+      protocol,
       companionOptions: { ...companionOptions, uploadUrls: [/^http:\/\/url.myendpoint.com\//] },
     }
 
@@ -33,6 +36,7 @@ describe('uploader with tus protocol', () => {
   test('uploader respects uploadUrls, valid', async () => {
     const opts = {
       endpoint: 'http://url.myendpoint.com/files',
+      protocol,
       companionOptions: { ...companionOptions, uploadUrls: [/^http:\/\/url.myendpoint.com\//] },
     }
 
@@ -43,6 +47,7 @@ describe('uploader with tus protocol', () => {
   test('uploader respects uploadUrls, localhost', async () => {
     const opts = {
       endpoint: 'http://localhost:1337/',
+      protocol,
       companionOptions: { ...companionOptions, uploadUrls: [/^http:\/\/localhost:1337\//] },
     }
 
@@ -226,6 +231,7 @@ describe('uploader with tus protocol', () => {
     const opts = {
       companionOptions,
       endpoint: 'http://localhost',
+      protocol,
     }
 
     // eslint-disable-next-line no-new
@@ -247,6 +253,7 @@ describe('uploader with tus protocol', () => {
   test('uploader respects maxFileSize correctly', async () => {
     const opts = {
       endpoint: 'http://url.myendpoint.com/files',
+      protocol,
       companionOptions: { ...companionOptions, maxFileSize: 100 },
       size: 99,
     }