Fix body parsing for x-www-form-urlencoded and empty

Form data posted with application/x-www-form-urlencoded
was ignored. This has been addressed and tested, and the body
is now populated.

The default handler now shows the content type received so
that users can understand what they are sending in via curl
or other mechanisms.

When no content-type was given, the template did not attempt to
do any form of parsing. This has been updated, so set a plain
text body type when the sender doesn't provide one.

Tested with node and express.js with various content-types.

A tech-debt item is that the body parser is now considered
deprecated, and a new parser needs to be moved to.

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

template/node12/function/handler.js

@@ -2,11 +2,11 @@
 
 module.exports = async (event, context) => {
   const result = {
-    'status': 'Received input: ' + JSON.stringify(event.body)
+    'body': JSON.stringify(event.body),
+    'content-type': event.headers["content-type"]
   }
 
   return context
     .status(200)
     .succeed(result)
 }
-

template/node12/index.js

@@ -9,18 +9,39 @@ const app = express()
 const handler = require('./function/handler');
 const bodyParser = require('body-parser')
 
+const defaultMaxSize = '100kb' // body-parser default
+
 app.disable('x-powered-by');
 
+const rawLimit = process.env.MAX_RAW_SIZE || defaultMaxSize
+const jsonLimit = process.env.MAX_JSON_SIZE || defaultMaxSize
+
+app.use(function addDefaultContentType(req, res, next) {
+    // When no content-type is given, the body element is set to 
+    // nil, and has been a source of contention for new users.
+
+    if(!req.headers['content-type']) {
+        req.headers['content-type'] = "text/plain"
+    }
+    next()
+})
+
 if (process.env.RAW_BODY === 'true') {
-    var rawLimit = process.env.MAX_RAW_SIZE || '100kb' // body-parser default
     app.use(bodyParser.raw({ type: '*/*' , limit: rawLimit }))
 } else {
-    var jsonLimit = process.env.MAX_JSON_SIZE || '100kb' //body-parser default
-    app.use(bodyParser.json({ limit: jsonLimit}));
-    app.use(bodyParser.raw()); // "Content-Type: application/octet-stream"
     app.use(bodyParser.text({ type : "text/*" }));
+    app.use(bodyParser.json({ limit: jsonLimit}));
+    app.use(bodyParser.urlencoded({ extended: true }));
 }
 
+const isArray = (a) => {
+    return (!!a) && (a.constructor === Array);
+};
+
+const isObject = (a) => {
+    return (!!a) && (a.constructor === Object);
+};
+
 class FunctionEvent {
     constructor(req) {
         this.body = req.body;
@@ -70,8 +91,8 @@ class FunctionContext {
     }
 }
 
-var middleware = async (req, res) => {
-    let cb = (err, functionResult) => {
+const middleware = async (req, res) => {
+    const cb = (err, functionResult) => {
         if (err) {
             console.error(err);
 
@@ -89,8 +110,8 @@ var middleware = async (req, res) => {
         }
     };
 
-    let fnEvent = new FunctionEvent(req);
-    let fnContext = new FunctionContext(cb);
+    const fnEvent = new FunctionEvent(req);
+    const fnContext = new FunctionContext(cb);
 
     Promise.resolve(handler(fnEvent, fnContext, cb))
     .then(res => {
@@ -113,13 +134,7 @@ app.options('/*', middleware);
 const port = process.env.http_port || 3000;
 
 app.listen(port, () => {
-    console.log(`OpenFaaS Node.js listening on port: ${port}`)
+    console.log(`node12 listening on port: ${port}`)
 });
 
-let isArray = (a) => {
-    return (!!a) && (a.constructor === Array);
-};
 
-let isObject = (a) => {
-    return (!!a) && (a.constructor === Object);
-};