Prevent form data from being consumed by Flask

[sohtsuka]

Event data unexpectedly becomes empty when invoking an API request with content types
multipart/form-data, application/x-www-form-urlencoded or application-x-url-encoded.

$ cat template.yaml
AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Resources:
    HelloWorldFunction:
        Type: AWS::Serverless::Function
        Properties:
            CodeUri: hello_world/build/
            Handler: app.lambda_handler
            Runtime: python2.7
            Events:
                HelloWorld:
                    Type: Api
                    Properties:
                        Path: /hello
                        Method: post

$ cat hello_world/build/app.py
import json

def lambda_handler(event, context):
    return {
        "statusCode": 200,
        "body": event['body']
    }

$ # sam local start-api

$ cat test.txt
TEST

$ curl -d @test.txt http://localhost:3000/hello
no data 

The cause is that Flask request's data property does not contain the data comes with these content types. get_data() method always returns raw data and seems to be more relevant.

After the changes:

$ # samdev local start-api

$ curl -d @test.txt http://localhost:3000/hello
TEST

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[billyshambrook]

This is needed to test slack commands.

[jfuss]

What you have here looks great! My only ask would be for both a functional and integration test, so that way we can catch regressions in this area. I would pick one of the headers (multipart/form-data, application/x-www-form-urlencoded or application-x-url-encoded) and check the data in the event. The tests can go into the TestService_EventSerialization Functional test class and in the TestServiceRequests Integration test class. You can follow this integ test as an example.

[sanathkr]

@sohtsuka Any chance you can add the functional & integration tests that @jfuss requested? These tests will greatly improve the value of your change by ensuring this behavior is never broken in future :)

[sohtsuka]

@jfuss @sanathkr Thanks for reviewing this. I'll try to add the tests.

[jfuss]

One small comment on the integ tests. It is strictly for readability but feel it is important to request a change for.

[jfuss]

I know this endpoint echoes the Event back but the path is specific to base64. For this case it wont affect the outcome but to keep things clean and readable, can you create a new path on the EchoEventFunction and update the path here.

[sanathkr]

LGTM

[jfuss]

:)

[sanathkr]

@sohtsuka I noticed this was your first PR. Congrats 🎉. Merged!