APIGateway Event Router using Regex

[seed-good]

I'm using Powertools for AWS Lambda with Python 3.10 and Powertools layer version 52 (but I can replicate this issue in layer version 71 as well). My lambda event router (APIGatewayRestResolver) uses regex because I need the same method to handle both /v1/foo as well as just /foo. My decorator for this looks like: @app.get("/v[0-9]/foo|/foo") (the [0-9] is just for future possibilities). This works fine except when I have a nested resource with a similar regex. If my nested resource is "bar", my method decorator for the method that needs to handle /foo/bar as well as /v1/foo/bar looks like @app.get("/v[0-9]/foo/bar|/foo/bar"). Attached is a simple lambda func to demo this.

The issue is that calls with path "/v1/foo/bar" get handled by the method for foo instead of the method for foo/bar.

To summarize:
The following work correctly (i.e. get routed to the right method):
/foo, /v1/foo, /foo/bar
The only path that does not get routed correctly is /v1/foo/bar

You can use the following API gateway URLs to see this. The response is either "got foo" or "got foo bar" depending on which of the 2 methods got invoked:

https://8viuioi1oe.execute-api.us-east-1.amazonaws.com/v1/foo
https://8viuioi1oe.execute-api.us-east-1.amazonaws.com/v1/foo/bar
https://8viuioi1oe.execute-api.us-east-1.amazonaws.com/v1/v1/foo
https://8viuioi1oe.execute-api.us-east-1.amazonaws.com/v1/v1/foo/bar

I am perplexed how /foo/bar gets routed correctly but the regex version /v1/foo/bar does not.
Any help/explanation will be appreciated!
test-regex-lambda.zip

[leandrodamascena]

Hey @seed-good! I was unable to reproduce this error here. I deployed the exactly Lambda you sent and I can access the resource correctly. I'm not saying it's not a possible bug or some other issue because I see this is failing in your case, but do you have anything additional to add here to help me reproduce the issue?

[seed-good]

Thanks for trying to re-produce the issue. It is interesting that it works for you. There's nothing special about my API gateway config - for this test it is public-facing API (while my real production issue is with a private API) with Lambda integration. I am attaching the OAS3 with API GW extensions export of my test API GW. If you don't mind, could you import the same and try again?
Also, did you use python 3.10 for your lambda runtime?
test-regex-api-v1-oas30-apigateway.zip

[seed-good]

@leandrodamascena Another interesting finding is that if I move the order of the 2 handler methods in the lambda func, putting the /foo/bar handler before the /foo handler, it works fine! This is how I have it now, so if you hit https://8viuioi1oe.execute-api.us-east-1.amazonaws.com/v1/v1/foo/bar now you should get the correct response ("got foo bar!"). I'm attaching the modified lambda here for your inspection. Why would the sequence matter?
test-regex-lambda-v2.zip

[leandrodamascena]

Hey @seed-good! I'll check tomorrow what's happening with this example you sent. I'm really curious to know what happens.