[WIP] Revert default behavior of writeHeaders method (#1104)

* Replace header key only

* Add preserveHeaderKeyCase Option

README.md

@@ -333,6 +333,7 @@ proxyServer.listen(8015);
 *  **ignorePath**: true/false, Default: false - specify whether you want to ignore the proxy path of the incoming request (note: you will have to append / manually if required).
 *  **localAddress**: Local interface string to bind for outgoing connections
 *  **changeOrigin**: true/false, Default: false - changes the origin of the host header to the target URL
+*  **preserveHeaderKeyCase**: true/false, Default: false - specify whether you want to keep letter case of response header key
 *  **auth**: Basic authentication i.e. 'user:password' to compute an Authorization header.
 *  **hostRewrite**: rewrites the location hostname on (201/301/302/307/308) redirects.
 *  **autoRewrite**: rewrites the location host/port on (201/301/302/307/308) redirects based on requested host/port. Default: false.

lib/http-proxy.js

@@ -35,6 +35,7 @@ function createProxyServer(options) {
    *    ignorePath: <true/false, Default: false - specify whether you want to ignore the proxy path of the incoming request>
    *    localAddress : <Local interface string to bind for outgoing connections>
    *    changeOrigin: <true/false, Default: false - changes the origin of the host header to the target URL>
+   *    preserveHeaderKeyCase: <true/false, Default: false - specify whether you want to keep letter case of response header key >
    *    auth   : Basic authentication i.e. 'user:password' to compute an Authorization header.
    *    hostRewrite: rewrites the location hostname on (301/302/307/308) redirects, Default: null.
    *    autoRewrite: rewrites the location host/port on (301/302/307/308) redirects based on requested host/port. Default: false.

lib/http-proxy/passes/web-outgoing.js

@@ -84,18 +84,14 @@ module.exports = { // <--
    */
   writeHeaders: function writeHeaders(req, res, proxyRes, options) {
     var rewriteCookieDomainConfig = options.cookieDomainRewrite,
-        // In proxyRes.rawHeaders Set-Cookie headers are sparse.
-        // so, we'll collect Set-Cookie headers, and set them in the response as an array.
-        setCookies = [],
+        preserveHeaderKeyCase = options.preserveHeaderKeyCase,
+        rawHeaderKeyMap,
         setHeader = function(key, header) {
           if (header == undefined) return;
-          if (key.toLowerCase() !== 'set-cookie') {
-            return res.setHeader(String(key).trim(), header);
-          }
-          if (rewriteCookieDomainConfig) {
+          if (rewriteCookieDomainConfig && key.toLowerCase() === 'set-cookie') {
             header = common.rewriteCookieDomain(header, rewriteCookieDomainConfig);
           }
-          setCookies.push(header); // defer to the end when we have all of them
+          res.setHeader(String(key).trim(), header);
         };
 
     if (typeof rewriteCookieDomainConfig === 'string') { //also test for ''
@@ -104,21 +100,21 @@ module.exports = { // <--
 
     // message.rawHeaders is added in: v0.11.6
     // https://nodejs.org/api/http.html#http_message_rawheaders
-    if (proxyRes.rawHeaders != undefined) {
+    if (preserveHeaderKeyCase && proxyRes.rawHeaders != undefined) {
+      rawHeaderKeyMap = {};
       for (var i = 0; i < proxyRes.rawHeaders.length; i += 2) {
         var key = proxyRes.rawHeaders[i];
-        var header = proxyRes.rawHeaders[i + 1];
-        setHeader(key, header);
+        rawHeaderKeyMap[key.toLowerCase()] = key;
       }
-    } else {
-      Object.keys(proxyRes.headers).forEach(function(key) {
-        var header = proxyRes.headers[key];
-        setHeader(key, header);
-      });
-    }
-    if (setCookies.length) {
-      res.setHeader('Set-Cookie', setCookies.length === 1 ? setCookies[0] : setCookies);
     }
+
+    Object.keys(proxyRes.headers).forEach(function(key) {
+      var header = proxyRes.headers[key];
+      if (preserveHeaderKeyCase && rawHeaderKeyMap) {
+        key = rawHeaderKeyMap[key] || key;
+      }
+      setHeader(key, header);
+    });
   },
 
   /**

test/lib-http-proxy-passes-web-outgoing-test.js

@@ -240,6 +240,14 @@ describe('lib/http-proxy/passes/web-outgoing.js', function () {
         }
       };
       this.rawProxyRes = {
+        headers: {
+          hey: 'hello',
+          how: 'are you?',
+          'set-cookie': [
+            'hello; domain=my.domain; path=/',
+            'there; domain=my.domain; path=/'
+          ]
+        },
         rawHeaders: [
           'Hey', 'hello',
           'How', 'are you?',
@@ -343,6 +351,11 @@ describe('lib/http-proxy/passes/web-outgoing.js', function () {
           'my.special.domain': 'my.special.domain'
         }
       };
+      this.rawProxyRes.headers['set-cookie'] = [
+        'hello-on-my.domain; domain=my.domain; path=/',
+        'hello-on-my.old.domain; domain=my.old.domain; path=/',
+        'hello-on-my.special.domain; domain=my.special.domain; path=/'
+      ];
       this.rawProxyRes.rawHeaders = this.rawProxyRes.rawHeaders.concat([
         'Set-Cookie',
         'hello-on-my.domain; domain=my.domain; path=/',

test/lib-http-proxy-test.js

@@ -130,7 +130,8 @@ describe('lib/http-proxy.js', function() {
     it('should make the request, handle response and finish it', function(done) {
       var ports = { source: gen.port, proxy: gen.port };
       var proxy = httpProxy.createProxyServer({
-        target: 'http://127.0.0.1:' + ports.source
+        target: 'http://127.0.0.1:' + ports.source,
+        preserveHeaderKeyCase: true
       }).listen(ports.proxy);
 
       var source = http.createServer(function(req, res) {