Allow agent option to be a function (#632)

edgraaff · bitinn · commit bf8b4e8db350 · 2019-05-05T20:12:33.000+08:00
Enable users to return HTTP/HTTPS-specific agent based on request url
diff --git a/README.md b/README.md
@@ -317,7 +317,7 @@ The default values are shown after each option key.
     timeout: 0,         // req/res timeout in ms, it resets on redirect. 0 to disable (OS limit applies). Signal is recommended instead.
     compress: true,     // support gzip/deflate content encoding. false to disable
     size: 0,            // maximum response body size in bytes. 0 to disable
-    agent: null         // http(s).Agent instance, allows custom proxy, certificate, dns lookup etc.
+    agent: null         // http(s).Agent instance (or function providing one), allows custom proxy, certificate, dns lookup etc.
 }
 ```
 
diff --git a/src/request.js b/src/request.js
@@ -230,7 +230,12 @@ export function getNodeRequestOptions(request) {
 		headers.set('Accept-Encoding', 'gzip,deflate');
 	}
 
-	if (!headers.has('Connection') && !request.agent) {
+	let agent = request.agent;
+	if (typeof agent === 'function') {
+		agent = agent(parsedURL);
+	}
+
+	if (!headers.has('Connection') && !agent) {
 		headers.set('Connection', 'close');
 	}
 
@@ -240,6 +245,6 @@ export function getNodeRequestOptions(request) {
 	return Object.assign({}, parsedURL, {
 		method: request.method,
 		headers: exportNodeCompatibleHeaders(headers),
-		agent: request.agent
+		agent
 	});
 }
diff --git a/test/test.js b/test/test.js
@@ -1978,6 +1978,30 @@ describe('node-fetch', () => {
 			expect(families[1]).to.equal(family);
 		});
 	});
+
+	it('should allow a function supplying the agent', function() {
+		const url = `${base}inspect`;
+
+		const agent = http.Agent({
+			keepAlive: true
+		});
+
+		let parsedURL;
+
+		return fetch(url, {
+			agent: function(_parsedURL) {
+				parsedURL = _parsedURL;
+				return agent;
+			}
+		}).then(res => {
+			return res.json();
+		}).then(res => {
+			// the agent provider should have been called
+			expect(parsedURL.protocol).to.equal('http:');
+			// the agent we returned should have been used
+			expect(res.headers['connection']).to.equal('keep-alive');
+		});
+	});
 });
 
 describe('Headers', function () {

Original file line number	Diff line number	Diff line change
`@@ -317,7 +317,7 @@ The default values are shown after each option key.`
`317`	`317`	`timeout: 0, // req/res timeout in ms, it resets on redirect. 0 to disable (OS limit applies). Signal is recommended instead.`
`318`	`318`	`compress: true, // support gzip/deflate content encoding. false to disable`
`319`	`319`	`size: 0, // maximum response body size in bytes. 0 to disable`
`320`		`- agent: null // http(s).Agent instance, allows custom proxy, certificate, dns lookup etc.`
	`320`	`+ agent: null // http(s).Agent instance (or function providing one), allows custom proxy, certificate, dns lookup etc.`
`321`	`321`	`}`
`322`	`322`	```
`323`	`323`
Original file line number	Diff line number	Diff line change
`@@ -230,7 +230,12 @@ export function getNodeRequestOptions(request) {`
`230`	`230`	`headers.set('Accept-Encoding', 'gzip,deflate');`
`231`	`231`	`}`
`232`	`232`
`233`		`- if (!headers.has('Connection') && !request.agent) {`
	`233`	`+ let agent = request.agent;`
	`234`	`+ if (typeof agent === 'function') {`
	`235`	`+ agent = agent(parsedURL);`
	`236`	`+ }`
	`237`	`+`
	`238`	`+ if (!headers.has('Connection') && !agent) {`
`234`	`239`	`headers.set('Connection', 'close');`
`235`	`240`	`}`
`236`	`241`
`@@ -240,6 +245,6 @@ export function getNodeRequestOptions(request) {`
`240`	`245`	`return Object.assign({}, parsedURL, {`
`241`	`246`	`method: request.method,`
`242`	`247`	`headers: exportNodeCompatibleHeaders(headers),`
`243`		`- agent: request.agent`
	`248`	`+ agent`
`244`	`249`	`});`
`245`	`250`	`}`