Bug: Event handler does not accept null header for compression

[tbuatois]

Expected Behaviour

As the documentation stated:
The client must send the Accept-Encoding header, otherwise a normal response will be sent.

When testing my API Gateway integration with lambda from the AWS Console, without specifying header, this send a null header.

Current Behaviour

Throw an error for a request with empty/null headers to a method with compress=True:
'NoneType' object has no attribute 'items'", "errorType": "AttributeError"

That was due to an error from api_gateway.py at line 212:

 if self.route.compress and "gzip" in (event.get_header_value("accept-encoding", "") or ""):

Code snippet

@tracer.capture_method
@app.post("/query/execute", compress=True)
def execute_query():

    query: dict = app.current_event.json_body
     .....
    return {"message": "OK"}


@tracer.capture_lambda_handler
@logger.inject_lambda_context(correlation_id_path=correlation_paths.API_GATEWAY_REST, log_event=True)
def lambda_handler(event, context):
    return app.resolve(event, context)

Possible Solution

No response

Steps to Reproduce

1. Create a AWS API Gateway type REST
2. Add a Lambda with routing
3. Enable compression for method, with compress=True
4. Test from API Gateway the method from AWS Console and do not specify headers

AWS Lambda Powertools for Python version

latest

AWS Lambda function runtime

3.9

Packaging format used

Lambda Layers

Debugging logs

....
Wed Jul 20 09:18:47 UTC 2022 : HTTP Method: POST, Resource Path: /query/execute
Wed Jul 20 09:18:47 UTC 2022 : Method request path: {}
Wed Jul 20 09:18:47 UTC 2022 : Method request query string: {}
Wed Jul 20 09:18:47 UTC 2022 : Method request headers: {}
Wed Jul 20 09:18:47 UTC 2022 : Method request body before transformations: {
.....
.....
Wed Jul 20 09:18:50 UTC 2022 : Endpoint response body before transformations: {"errorMessage": "'NoneType' object has no attribute 'items'", "errorType": "AttributeError", "requestId": "REDACTED", "stackTrace": ["  File \"/opt/python/aws_lambda_powertools/tracing/tracer.py\", line 315, in decorate\n    response = lambda_handler(event, context, **kwargs)\n", "  File \"/opt/python/aws_lambda_powertools/logging/logger.py\", line 354, in decorate\n    return lambda_handler(event, context, *args, **kwargs)\n", "  File \"/var/task/app.py\", line 59, in lambda_handler\n    return app.resolve(event, context)\n", "  File \"/opt/python/aws_lambda_powertools/event_handler/api_gateway.py\", line 503, in resolve\n    return self._resolve().build(self.current_event, self._cors)\n", "  File \"/opt/python/aws_lambda_powertools/event_handler/api_gateway.py\", line 217, in build\n    self._route(event, cors)\n", "  File \"/opt/python/aws_lambda_powertools/event_handler/api_gateway.py\", line 212, in _route\n    if self.route.comp [TRUNCATED]
Wed Jul 20 09:18:50 UTC 2022 : Lambda execution failed with status 200 due to customer function error: 'NoneType' object has no attribute 'items'. Lambda request id: REDACTED
Wed Jul 20 09:18:50 UTC 2022 : Method completed with status: 502

[boring-cyborg]

Thanks for opening your first issue here! We'll come back to you as soon as we can.

[heitorlessa]

hey @tbuatois thank you for flagging this and even for taking the time to solve it, much appreciated! Question for you: can this wait until our next release this Friday or is that impacting you now?

I suspect it's the former

[tbuatois]

hey @tbuatois thank you for flagging this and even for taking the time to solve it, much appreciated! Question for you: can this wait until our next release this Friday or is that impacting you now?

I suspect it's the former

Hey @heitorlessa,

It can surely wait for the next release ! Thanks for asking.

[github-actions]

This is now released under 1.26.6 version!