fix: Content-Length header automatically filled if it's not exists

AWS API Gateway doesn't pass content-length header to lambda function.
As a result of this body-parser can not parse body. This fix calculates
Content-Length with the size of body if there is no content-length
header and if there is a body.

Author: muratcorlu

README.md

@@ -128,9 +128,3 @@ Every contribution is very welcome. Keep these in your mind when you want to mak
 2. Keep code coverage 100% with your updated tests.
 3. Check your changes with a Lambda environment. You can use [SAM-CLI](https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/what-is-sam.html) to test on your local.
 4. Don't forget to update documentation(this readme file) about your changes.
-
-## Troubleshooting
-
-### I'm making a POST request with JSON by using bodyParser as middleware but `req.body` is always `{}`
-
-Please check your `Content-Type` and `Content-Length` request headers. For JSON requests `Content-Type` should be `application/json` and `Content-Length` should be size(in bytes) of JSON string in body.

src/request.js

@@ -30,6 +30,10 @@ class Request extends ReadableStream {
     this.path = event.path;
     this.params = event.pathParameters;
 
+    if (!this.get('Content-Length') && 'body' in event && event.body !== null) {
+      this.headers['content-length'] = event.body.length;
+    }
+
     this.protocol = this.get('X-Forwarded-Proto')
     this.secure = this.protocol === 'https';
     this.ips = (this.get('X-Forwarded-For') || '').split(', ');

src/request.spec.js

@@ -69,6 +69,7 @@ describe('Request object', () => {
 
   it('should read headers as empty object if there is no headers', () => {
     delete event.multiValueHeaders;
+    delete event.body;
     const request = new Request(event);
 
     expect(request.headers).toEqual({});
@@ -136,4 +137,13 @@ describe('Request object', () => {
     expect(request.acceptsLanguages('tr', 'en')).toBe('tr');
 
   });
+
+  it('should handle content-length header if its not provided', () => {
+    delete event.headers['content-length'];
+    delete event.multiValueHeaders['content-length'];
+
+    const request = new Request(event);
+    const body = JSON.stringify(requestObject);
+    expect(request.get('content-length')).toBe(body.length);
+  })
 });