From fd05b32f04eb9c20f0a8daddcf7d71c530d85c36 Mon Sep 17 00:00:00 2001
From: Nik 'Fire Eater' Krimm <nkrimm@signal.co>
Date: Thu, 7 Mar 2019 09:58:21 -0600
Subject: [PATCH] [#399]: Clarifies behavior on empty response body.

---
 README.md                | 19 +++++++++++++------
 test/userResDecorator.js | 39 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+), 6 deletions(-)

diff --git a/README.md b/README.md
index 711f9da3..72b6016f 100644
--- a/README.md
+++ b/README.md
@@ -142,25 +142,32 @@ Promise form:
 
 ```js
   app.use(proxy('localhost:12346', {
-    filter: function (req, res) { 
-      return new Promise(function (resolve) { 
+    filter: function (req, res) {
+      return new Promise(function (resolve) {
         resolve(req.method === 'GET');
-      }); 
+      });
     }
   }));
 ```
 
 Note that in the previous example, `resolve(false)` will execute the happy path
 for filter here (skipping the rest of the proxy, and calling `next()`).
-`reject()` will also skip the rest of proxy and call `next()`. 
+`reject()` will also skip the rest of proxy and call `next()`.
 
 #### userResDecorator (was: intercept) (supports Promise)
 
 You can modify the proxy's response before sending it to the client.
 
+Note: `proxyResData` will be an empty buffer when the proxied response is empty.
+
 ```js
 app.use('/proxy', proxy('www.google.com', {
   userResDecorator: function(proxyRes, proxyResData, userReq, userRes) {
+    if (proxyResData.length == 0) {
+      // body is empty, don't try to parse it
+      // return alternate document instead.
+      return JSON.stringify({});
+    }
     data = JSON.parse(proxyResData.toString('utf8'));
     data.newProperty = 'exciting data';
     return JSON.stringify(data);
@@ -562,9 +569,9 @@ app.use('/', proxy('internalhost.example.com', {
 | --- | --- |
 | 1.5.1 | Fixes bug in stringifying debug messages. |
 | 1.5.0 | Fixes bug in `filter` signature.  Fix bug in skipToNextHandler, add expressHttpProxy value to user res when skipped.  Add tests for host as ip address. |
-| 1.4.0 | DEPRECATED. Critical bug in the `filter` api.| 
+| 1.4.0 | DEPRECATED. Critical bug in the `filter` api.|
 | 1.3.0 | DEPRECATED. Critical bug in the `filter` api. `filter` now supports Promises.  Update linter to eslint.  |
-| 1.2.0 | Auto-stream when no decorations are made to req/res. Improved docs, fixes issues in maybeSkipToNexthandler,  allow authors to manage error handling. | 
+| 1.2.0 | Auto-stream when no decorations are made to req/res. Improved docs, fixes issues in maybeSkipToNexthandler,  allow authors to manage error handling. |
 | 1.1.0 | Add step to allow response headers to be modified.
 | 1.0.7 | Update dependencies.  Improve docs on promise rejection.   Fix promise rejection on body limit.   Improve debug output. |
 | 1.0.6 | Fixes preserveHostHdr not working, skip userResDecorator on 304, add maybeSkipToNext, test improvements and cleanup. |
diff --git a/test/userResDecorator.js b/test/userResDecorator.js
index 150b6a3e..0332b63e 100644
--- a/test/userResDecorator.js
+++ b/test/userResDecorator.js
@@ -4,6 +4,7 @@ var assert = require('assert');
 var express = require('express');
 var request = require('supertest');
 var proxy = require('../');
+var http = require('http');
 
 describe('userResDecorator', function () {
 
@@ -39,6 +40,44 @@ describe('userResDecorator', function () {
     });
   });
 
+  describe('when handling a response with no body', function () {
+    this.timeout(10000);
+
+    var app;
+    var noBodyTarget;
+    var serverReference;
+    var responseCode = 200;
+
+    beforeEach(function () {
+      app = express();
+      noBodyTarget = new http.Server();
+      noBodyTarget.on('request', function (req, res) {
+        res.writeHead(responseCode, { 'Content-Length': '0' });
+        res.end();
+      });
+      serverReference = noBodyTarget.listen(12346);
+    });
+
+    afterEach(function () {
+      serverReference.close();
+    });
+
+
+    it('returns an empty Buffer for the proxyResData', function (done) {
+      app.use('/proxy', proxy('http://127.0.0.1:12346', {
+        userResDecorator: function (proxyRes, proxyResData /*, userReq, userRes */) {
+          assert(Buffer.isBuffer(proxyResData));
+          assert(proxyResData.length === 0);
+        }
+      }));
+
+      request(app)
+        .get('/proxy')
+        .expect(200)
+        .end(done);
+    });
+  });
+
   it('has access to original response', function (done) {
     var app = express();
     app.use(proxy('httpbin.org', {