From ecf23dcd9e805ca43a738dbd266f6c2a25b45601 Mon Sep 17 00:00:00 2001
From: Anna Henningsen <anna@addaleax.net>
Date: Wed, 7 Aug 2024 15:22:14 +0200
Subject: [PATCH] Pass `req` to `getProxyForUrl` callback

This allows more flexibility in the callback, e.g. for inspecting
request headers before deciding on a given proxy.
---
 .changeset/sixty-carpets-cross.md | 5 +++++
 packages/proxy-agent/src/index.ts | 8 ++++----
 packages/proxy-agent/test/test.ts | 5 ++++-
 3 files changed, 13 insertions(+), 5 deletions(-)
 create mode 100644 .changeset/sixty-carpets-cross.md

diff --git a/.changeset/sixty-carpets-cross.md b/.changeset/sixty-carpets-cross.md
new file mode 100644
index 00000000..2dd6a905
--- /dev/null
+++ b/.changeset/sixty-carpets-cross.md
@@ -0,0 +1,5 @@
+---
+'proxy-agent': minor
+---
+
+Include ClientRequest in getProxyForUrl parameters for additional flexibility
diff --git a/packages/proxy-agent/src/index.ts b/packages/proxy-agent/src/index.ts
index 496e185a..83612e5b 100644
--- a/packages/proxy-agent/src/index.ts
+++ b/packages/proxy-agent/src/index.ts
@@ -22,7 +22,7 @@ type ValidProtocol = (typeof PROTOCOLS)[number];
 
 type AgentConstructor = new (...args: never[]) => Agent;
 
-type GetProxyForUrlCallback = (url: string) => string | Promise<string>;
+type GetProxyForUrlCallback = (url: string, req: http.ClientRequest) => string | Promise<string>;
 
 /**
  * Supported proxy types.
@@ -69,7 +69,7 @@ export type ProxyAgentOptions = HttpProxyAgentOptions<''> &
 		 * Defaults to standard proxy environment variables,
 		 * see https://www.npmjs.com/package/proxy-from-env for details
 		 */
-		getProxyForUrl?: GetProxyForUrlCallback;
+		getProxyForUrl: GetProxyForUrlCallback;
 	};
 
 /**
@@ -90,7 +90,7 @@ export class ProxyAgent extends Agent {
 	httpsAgent: http.Agent;
 	getProxyForUrl: GetProxyForUrlCallback;
 
-	constructor(opts?: ProxyAgentOptions) {
+	constructor(opts: ProxyAgentOptions) {
 		super(opts);
 		debug('Creating new ProxyAgent instance: %o', opts);
 		this.connectOpts = opts;
@@ -115,7 +115,7 @@ export class ProxyAgent extends Agent {
 			: 'http:';
 		const host = req.getHeader('host');
 		const url = new URL(req.path, `${protocol}//${host}`).href;
-		const proxy = await this.getProxyForUrl(url);
+		const proxy = await this.getProxyForUrl(url, req);
 
 		if (!proxy) {
 			debug('Proxy not enabled for URL: %o', url);
diff --git a/packages/proxy-agent/test/test.ts b/packages/proxy-agent/test/test.ts
index 2544d182..8e8f0f4b 100644
--- a/packages/proxy-agent/test/test.ts
+++ b/packages/proxy-agent/test/test.ts
@@ -266,15 +266,17 @@ describe('ProxyAgent', () => {
 		it('should call provided function with getProxyForUrl option', async () => {
 			let gotCall = false;
 			let urlParameter = '';
+			let reqParameter: http.ClientRequest | undefined;
 			httpsServer.once('request', function (req, res) {
 				res.end(JSON.stringify(req.headers));
 			});
 
 			const agent = new ProxyAgent({
 				rejectUnauthorized: false,
-				getProxyForUrl: (u) => {
+				getProxyForUrl: (u, r) => {
 					gotCall = true;
 					urlParameter = u;
+					reqParameter = r;
 					return httpsProxyServerUrl.href;
 				},
 			});
@@ -287,6 +289,7 @@ describe('ProxyAgent', () => {
 			assert(httpsServerUrl.host === body.host);
 			assert(gotCall);
 			assert(requestUrl.href === urlParameter);
+			assert(reqParameter?.constructor.name === 'ClientRequest');
 		});
 
 		it('should call provided function with asynchronous getProxyForUrl option', async () => {