[#272] Workflow step for modifying headers. (#287)

README.md

@@ -187,6 +187,18 @@ request, and all additional requests would return the value resolved on the
 first request.
 
 
+### userResHeaderDecorator
+
+```js
+app.use('/proxy', proxy('www.google.com', {
+  userResHeaderDecorator(headers, userReq, userRes, proxyReq, proxyRes) {
+    // recieves an Object of headers, returns an Object of headers.
+    return headers;
+  }
+}));
+```
+
+
 #### decorateRequest
 
 REMOVED:  See ```proxyReqOptDecorator``` and ```proxyReqBodyDecorator```.

app/steps/decorateUserResHeaders.js

@@ -0,0 +1,22 @@
+'use strict';
+
+
+function decorateUserResHeaders(container) {
+  var resolverFn = container.options.userResHeaderDecorator;
+  var headers = container.user.res._headers;
+
+  if (!resolverFn) {
+    return Promise.resolve(container);
+  }
+
+  return Promise
+    .resolve(resolverFn(headers, container.user.req, container.user.res, container.proxy.req, container.proxy.res))
+    .then(function(headers) {
+      return new Promise(function(resolve) {
+        container.user.res.set(headers);
+        resolve(container);
+      });
+    });
+}
+
+module.exports = decorateUserResHeaders;

index.js

@@ -24,6 +24,7 @@ var copyProxyResHeadersToUserRes = require('./app/steps/copyProxyResHeadersToUse
 var decorateProxyReqBody         = require('./app/steps/decorateProxyReqBody');
 var decorateProxyReqOpts         = require('./app/steps/decorateProxyReqOpts');
 var decorateUserRes              = require('./app/steps/decorateUserRes');
+var decorateUserResHeaders       = require('./app/steps/decorateUserResHeaders');
 var maybeSkipToNextHandler       = require('./app/steps/maybeSkipToNextHandler');
 var prepareProxyReq              = require('./app/steps/prepareProxyReq');
 var resolveProxyHost             = require('./app/steps/resolveProxyHost');
@@ -51,6 +52,7 @@ module.exports = function proxy(host, userOptions) {
       .then(sendProxyRequest)
       .then(maybeSkipToNextHandler)
       .then(copyProxyResHeadersToUserRes)
+      .then(decorateUserResHeaders)
       .then(decorateUserRes)
       .then(sendUserRes)
       .catch(next);

lib/resolveOptions.js

@@ -37,6 +37,7 @@ function resolveOptions(options) {
     proxyReqOptDecorator: options.proxyReqOptDecorator,
     proxyReqBodyDecorator: options.proxyReqBodyDecorator,
     userResDecorator: options.userResDecorator || options.intercept,
+    userResHeaderDecorator: options.userResHeaderDecorator,
     filter: options.filter || defaultFilter,
     // For backwards compatability, we default to legacy behavior for newly added settings.
     parseReqBody: isUnset(options.parseReqBody) ? true : options.parseReqBody,

test/decorateUserResHeaders.js

@@ -0,0 +1,49 @@
+'use strict';
+
+var assert = require('assert');
+var express = require('express');
+var request = require('supertest');
+var proxy = require('../');
+
+describe('when userResHeaderDecorator is defined', function() {
+
+  this.timeout(10000);
+
+  var app, serverReference;
+
+  afterEach(function() {
+    serverReference.close();
+  });
+
+  beforeEach(function() {
+    app = express();
+    var pTarget = express();
+    pTarget.use(function(req, res) { res.json(req.headers); });
+    serverReference = pTarget.listen(12345);
+  });
+
+  afterEach(function() {
+    serverReference.close();
+  });
+
+  it('provides an interface for updating headers', function(done) {
+
+    app.use('/proxy', proxy('http://127.0.0.1:12345', {
+      userResHeaderDecorator: function(headers /*, userReq, userRes, proxyReq, proxyRes */) {
+        headers.boltedonheader = 'franky';
+        return headers;
+      }
+    }));
+
+    app.use(function(req, res) {
+      res.sendStatus(200);
+    });
+
+    request(app)
+      .get('/proxy')
+      .expect(function(res) {
+        assert(res.headers.boltedonheader === 'franky');
+      })
+      .end(done);
+  });
+});