fix: Use PassThrough instead of stubbing (#306)

Author: matthew-plusprogramming

lib/request.js

@@ -1,17 +1,17 @@
 'use strict';
 
 const http = require('http');
+const { PassThrough } = require('stream');
 
 module.exports = class ServerlessRequest extends http.IncomingMessage {
   constructor({ method, url, headers, body, remoteAddress }) {
-    super({
-      encrypted: true,
-      readable: false,
-      remoteAddress,
-      address: () => ({ port: 443 }),
-      end: Function.prototype,
-      destroy: Function.prototype
-    });
+    // Create a real readable socket for IncomingMessage instead of a stub.
+    const socket = new PassThrough();
+    socket.encrypted = true;
+    socket.remoteAddress = remoteAddress;
+    socket.address = () => ({ port: 443 });
+
+    super(socket);
 
     if (typeof headers['content-length'] === 'undefined') {
       headers['content-length'] = Buffer.byteLength(body);
@@ -29,10 +29,18 @@ module.exports = class ServerlessRequest extends http.IncomingMessage {
       url,
     });
 
+    // Make the request stream readable by pushing the body when consumed.
     this._read = () => {
-      this.push(body);
+      if (typeof body !== 'undefined' && body !== null) {
+        this.push(body);
+      }
       this.push(null);
     };
-  }
 
-}
+    // If there's no body, emit 'end' on next tick so on-finished(req) fires
+    // even when no one consumes the stream.
+    if (!body || Buffer.byteLength(body) === 0) {
+      setImmediate(() => this.emit('end'));
+    }
+  }
+};