raw_body property inconsistency

[johntmyers]

When no body is sent, and app.current_request.raw_body is used, there is inconsistent behavior between local Chalice testing and actually how it runs in Lambda.

For local testing, if no body is sent self._body is getting set to a string: {}

However, when no body is provided in an actual call to API gateway, self._body is None and there is an unhandled AttributeError exception when this executes: self._raw_body = self._body.encode('utf-8')

This effectively makes it hard for an app developer to gracefully handle a missing body from a call and will always yield a 500 error back to the user.

I personally see no reason to catch if body is None within local.py this effectively gives a false impression of how a request will be handled by Lambda itself. Instead the None type should be handled within the raw_body property IMO.

Relevant code in app.py:

@property
    def raw_body(self):
        if self._raw_body is None:
            if self._is_base64_encoded:
                self._raw_body = self._base64decode(self._body)
            elif not isinstance(self._body, bytes):
                self._raw_body = self._body.encode('utf-8')
            else:
                self._raw_body = self._body
        return self._raw_body

Relevant code in local.py:

def create_lambda_event(self, method, path, headers, body=None):
        # type: (str, str, Dict[str, str], str) -> EventType
        view_route = self._route_matcher.match_route(path)
        event = {
            'requestContext': {
                'httpMethod': method,
                'resourcePath': view_route.route,
                'identity': {
                    'sourceIp': self.LOCAL_SOURCE_IP
                },
            },
            'headers': dict(headers),
            'queryStringParameters': view_route.query_params,
            'pathParameters': view_route.captured,
            'stageVariables': {},
        }
        # if body is None:
        #    event['body'] = '{}'
        if self._is_binary(headers):
            event['body'] = base64.b64encode(body).decode('ascii')
            event['isBase64Encoded'] = True
        else:
            event['body'] = body
        return event

[johntmyers]

Note that I commented out the setting of body to "{}" here to validate

[jamesls]

Confirmed bug:

@app.route('/')
def index():
    return {'hello': repr(app.current_request.raw_body)}

Traceback (most recent call last):
  File "/var/task/chalice/app.py", line 647, in _get_view_function_response
    response = view_function(**function_args)
  File "/var/task/app.py", line 9, in index
    return {'hello': repr(app.current_request.raw_body)}
  File "/var/task/chalice/app.py", line 284, in raw_body
    self._raw_body = self._body.encode('utf-8')
AttributeError: 'NoneType' object has no attribute 'encode'

I think setting this value to None/empty string makes sense for both chalice local and on actual Lambda.

Thanks for reporting.