Fix custom Host header with arbitrary case (node-fetch#430)

Regression since 1592ca1.

Fixes: node-fetch#416
Fixes: node-fetch#425

Author: TimothyGu

src/headers.js

@@ -323,6 +323,25 @@ Object.defineProperty(HeadersIteratorPrototype, Symbol.toStringTag, {
 	configurable: true
 });
 
+/**
+ * Export the Headers object in a form that Node.js can consume.
+ *
+ * @param   Headers  headers
+ * @return  Object
+ */
+export function exportNodeCompatibleHeaders(headers) {
+	const obj = Object.assign({ __proto__: null }, headers[MAP]);
+
+	// http.request() only supports string as Host header. This hack makes
+	// specifying custom Host header possible.
+	const hostHeaderKey = find(headers[MAP], 'Host');
+	if (hostHeaderKey !== undefined) {
+		obj[hostHeaderKey] = obj[hostHeaderKey][0];
+	}
+
+	return obj;
+}
+
 /**
  * Create a Headers object from an object of headers, ignoring those that do
  * not conform to HTTP grammar productions.

src/index.js

@@ -43,11 +43,6 @@ export default function fetch(url, opts) {
 
 		const send = (options.protocol === 'https:' ? https : http).request;
 
-		// http.request only support string as host header, this hack make custom host header possible
-		if (options.headers.host) {
-			options.headers.host = options.headers.host[0];
-		}
-
 		// send request
 		const req = send(options);
 		let reqTimeout;

src/request.js

@@ -7,7 +7,7 @@
  * All spec algorithm step numbers are based on https://fetch.spec.whatwg.org/commit-snapshots/ae716822cb3a61843226cd090eefc6589446c1d2/.
  */
 
-import Headers from './headers.js';
+import Headers, { exportNodeCompatibleHeaders } from './headers.js';
 import Body, { clone, extractContentType, getTotalBytes } from './body';
 
 const { format: format_url, parse: parse_url } = require('url');
@@ -200,7 +200,7 @@ export function getNodeRequestOptions(request) {
 
 	return Object.assign({}, parsedURL, {
 		method: request.method,
-		headers: headers.raw(),
+		headers: exportNodeCompatibleHeaders(headers),
 		agent: request.agent
 	});
 }

test/test.js

@@ -208,6 +208,20 @@ describe('node-fetch', () => {
 		});
 	});
 
+	it('should accept custom HoSt header', function() {
+		const url = `${base}inspect`;
+		const opts = {
+			headers: {
+				HoSt: 'example.com'
+			}
+		};
+		return fetch(url, opts).then(res => {
+			return res.json();
+		}).then(res => {
+			expect(res.headers['host']).to.equal('example.com');
+		});
+	});
+
 	it('should follow redirect code 301', function() {
 		const url = `${base}redirect/301`;
 		return fetch(url).then(res => {