Proxy headers from server request to Got (#772)

migration-guides.md

@@ -134,19 +134,23 @@ Hooks are powerful, aren't they? [Read more](readme.md#hooks) to see what else y
 Let's take a quick look at another example from Request's readme:
 
 ```js
-http.createServer((req, res) => {
-	if (req.url === '/doodle.png') {
-		req.pipe(request('https://example.com/doodle.png')).pipe(res);
+http.createServer((request, response) => {
+	if (request.url === '/doodle.png') {
+		request.pipe(request('https://example.com/doodle.png')).pipe(response);
 	}
 });
 ```
 
 The cool feature here is that Request can proxy headers with the stream, but Got can do that too:
 
 ```js
-http.createServer((req, res) => {
-	if (req.url === '/doodle.png') {
-		req.pipe(got.stream('https://example.com/doodle.png')).pipe(res);
+http.createServer((request, response) => {
+	if (request.url === '/doodle.png') {
+		// When someone makes a request to our server, we receive a body and some headers.
+		// These are passed to Got. Got proxies received data to our server response,
+		// so you don't have to do `response.writeHead(statusCode, headers)` and `response.end(body)`.
+		// It's done automatically.
+		request.pipe(got.stream('https://example.com/doodle.png')).pipe(response);
 	}
 });
 ```

source/as-stream.ts

@@ -1,4 +1,5 @@
 import {PassThrough as PassThroughStream, Duplex as DuplexStream} from 'stream';
+import {IncomingMessage} from 'http';
 import duplexer3 from 'duplexer3';
 import requestAsEventEmitter from './request-as-event-emitter';
 import {HTTPError, ReadError} from './errors';
@@ -105,6 +106,15 @@ export default function asStream(options: MergedOptions) {
 		return unpipe(stream);
 	};
 
+	proxy.on('pipe', source => {
+		if (source instanceof IncomingMessage) {
+			options.headers = {
+				...source.headers,
+				...options.headers
+			};
+		}
+	});
+
 	proxy.isFromCache = undefined;
 
 	return proxy;

source/utils/types.ts

@@ -139,7 +139,7 @@ export interface Options extends Omit<https.RequestOptions, 'agent'> {
 	agent: http.Agent | https.Agent | boolean | AgentByProtocol;
 	gotTimeout?: number | Delays;
 	cache?: string | StorageAdapter;
-	headers?: {[key: string]: string};
+	headers?: {[key: string]: string | string[]};
 	// TODO: Remove this once TS migration is complete and all options are defined.
 	[key: string]: unknown;
 }

test/stream.ts

@@ -30,6 +30,10 @@ const errorHandler = (_request, response) => {
 	response.end();
 };
 
+const headersHandler = (request, response) => {
+	response.end(JSON.stringify(request.headers));
+};
+
 test('`options.responseType` is ignored', withServer, async (t, server, got) => {
 	server.get('/', defaultHandler);
 
@@ -157,6 +161,20 @@ test('proxying headers works', withServer, async (t, server, got) => {
 	t.is(body, 'ok');
 });
 
+test('piping server request to Got proxies also headers', withServer, async (t, server, got) => {
+	server.get('/', headersHandler);
+	server.get('/proxy', (request, response) => {
+		request.pipe(got.stream('')).pipe(response);
+	});
+
+	const {foo} = await got('proxy', {
+		headers: {
+			foo: 'bar'
+		}
+	}).json();
+	t.is(foo, 'bar');
+});
+
 test('skips proxying headers after server has sent them already', withServer, async (t, server, got) => {
 	server.get('/', defaultHandler);
 	server.get('/proxy', (_request, response) => {