http: add CONNECT method handling for default Host header when using proxy

lib/_http_client.js

@@ -375,18 +375,22 @@ function ClientRequest(input, options, cb) {
     if (host && !this.getHeader('host') && setHost) {
       let hostHeader = host;
 
-      // For the Host header, ensure that IPv6 addresses are enclosed
-      // in square brackets, as defined by URI formatting
-      // https://tools.ietf.org/html/rfc3986#section-3.2.2
-      const posColon = hostHeader.indexOf(':');
-      if (posColon !== -1 &&
-          hostHeader.includes(':', posColon + 1) &&
-          hostHeader.charCodeAt(0) !== 91/* '[' */) {
-        hostHeader = `[${hostHeader}]`;
-      }
+      if (method === 'CONNECT' && options.path) {
+        hostHeader = String(this.path);
+      } else {
+        // For the Host header, ensure that IPv6 addresses are enclosed
+        // in square brackets, as defined by URI formatting
+        // https://tools.ietf.org/html/rfc3986#section-3.2.2
+        const posColon = hostHeader.indexOf(':');
+        if (posColon !== -1 &&
+            hostHeader.includes(':', posColon + 1) &&
+            hostHeader.charCodeAt(0) !== 91/* '[' */) {
+          hostHeader = `[${hostHeader}]`;
+        }
 
-      if (port && +port !== defaultPort) {
-        hostHeader += ':' + port;
+        if (port && +port !== defaultPort) {
+          hostHeader += ':' + port;
+        }
       }
       this.setHeader('Host', hostHeader);
     }

test/parallel/test-http-connect-default-host-header.js

@@ -0,0 +1,37 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const http = require('http');
+const net = require('net');
+
+const target = 'target.example.com:443';
+
+const server = net.createServer(common.mustCall((socket) => {
+  socket.once('data', common.mustCall((data) => {
+    const rawRequest = data.toString();
+    const requestLines = rawRequest.split('\r\n');
+
+    assert.strictEqual(requestLines[0], `CONNECT ${target} HTTP/1.1`);
+    assert(requestLines.includes(`Host: ${target}`));
+
+    socket.end('HTTP/1.1 200 Connection established\r\n\r\n');
+  }));
+}));
+
+server.listen(0, common.localhostIPv4, common.mustCall(() => {
+  const req = http.request({
+    host: common.localhostIPv4,
+    port: server.address().port,
+    method: 'CONNECT',
+    path: target,
+  }, common.mustNotCall());
+
+  req.on('connect', common.mustCall((res, socket) => {
+    assert.strictEqual(res.statusCode, 200);
+    socket.destroy();
+    server.close();
+  }));
+
+  req.end();
+}));