fix(fetch): do not assign default value to RequestInit.method

lib/fetch/index.js

@@ -95,7 +95,7 @@ class Fetch extends EE {
 }
 
 // https://fetch.spec.whatwg.org/#fetch-method
-async function fetch (input, init = undefined) {
+async function fetch (input, init = {}) {
   if (arguments.length < 1) {
     throw new TypeError(
       `Failed to execute 'fetch' on 'Window': 1 argument required, but only ${arguments.length} present.`

lib/fetch/request.js

@@ -843,8 +843,7 @@ webidl.converters.AbortSignal = webidl.interfaceConverter(
 webidl.converters.RequestInit = webidl.dictionaryConverter([
   {
     key: 'method',
-    converter: webidl.converters.ByteString,
-    defaultValue: 'GET'
+    converter: webidl.converters.ByteString
   },
   {
     key: 'headers',

test/fetch/client-fetch.js

@@ -9,6 +9,7 @@ const { Blob } = require('buffer')
 const { fetch, Response, Request, FormData, File } = require('../..')
 const { Client, setGlobalDispatcher, Agent } = require('../..')
 const nodeFetch = require('../../index-fetch')
+const { once } = require('events')
 
 setGlobalDispatcher(new Agent({
   keepAliveTimeout: 1,
@@ -419,3 +420,23 @@ test('error on redirect', async (t) => {
     t.equal(errorCause.message, 'unexpected redirect')
   })
 })
+
+// https://github.com/nodejs/undici/issues/1527
+test('fetching with Request object - issue #1527', async (t) => {
+  const server = createServer((req, res) => {
+    t.pass()
+    res.end()
+  }).listen(0)
+
+  t.teardown(server.close.bind(server))
+  await once(server, 'listening')
+
+  const body = JSON.stringify({ foo: 'bar' })
+  const request = new Request(`http://localhost:${server.address().port}`, {
+    method: 'POST',
+    body
+  })
+
+  await t.resolves(fetch(request))
+  t.end()
+})