Resolves issue #59 (#60)

* Add failing test

* Resolve issue 59

index.js

@@ -63,9 +63,11 @@ module.exports = fp(function from (fastify, opts, next) {
       if (this.request.body instanceof Stream) {
         body = this.request.body
       } else {
-        body = JSON.stringify(this.request.body)
+        // Per RFC 7231 §3.1.1.5 if this header is not present we MAY assume application/octet-stream
+        const contentType = req.headers['content-type'] || 'application/octet-stream'
+        body = contentType.toLowerCase() === 'application/json' ? JSON.stringify(this.request.body) : this.request.body
         headers['content-length'] = Buffer.byteLength(body)
-        headers['content-type'] = 'application/json'
+        headers['content-type'] = contentType
       }
     }
 

test/post-plain-text.js

@@ -0,0 +1,56 @@
+'use strict'
+
+const t = require('tap')
+const Fastify = require('fastify')
+const From = require('..')
+const http = require('http')
+const get = require('simple-get').concat
+
+const instance = Fastify()
+instance.register(From)
+
+t.plan(9)
+t.tearDown(instance.close.bind(instance))
+
+const target = http.createServer((req, res) => {
+  t.pass('request proxied')
+  t.equal(req.method, 'POST')
+  t.equal(req.headers['content-type'], 'text/plain')
+  var data = ''
+  req.setEncoding('utf8')
+  req.on('data', (d) => {
+    data += d
+  })
+  req.on('end', () => {
+    const str = data.toString()
+    t.deepEqual(str, 'this is plain text')
+    res.statusCode = 200
+    res.setHeader('content-type', 'text/plain')
+    res.end(str)
+  })
+})
+
+instance.post('/', (request, reply) => {
+  reply.from(`http://localhost:${target.address().port}`)
+})
+
+t.tearDown(target.close.bind(target))
+
+instance.listen(0, (err) => {
+  t.error(err)
+
+  target.listen(0, (err) => {
+    t.error(err)
+
+    get({
+      url: `http://localhost:${instance.server.address().port}`,
+      method: 'POST',
+      headers: { 'content-type': 'text/plain' },
+      body: 'this is plain text'
+    }, (err, res, data) => {
+      t.error(err)
+      t.equal(res.headers['content-type'], 'text/plain')
+      t.deepEqual(data.toString(), 'this is plain text')
+    })
+  })
+})