Bug: APIGatewayRestResolver does not capture path segment with + sign

[nejcskofic]

Expected Behaviour

If handler is registered for dynamic path, I would expect that segment containing plus sign is captured.

Example:

@app.get("/dummy/<value>")
def handler(value: str): ...

Resolver is invoked with: GET /dummy/a+b

Current Behaviour

Resolver returns 404 error.

Code snippet

from dataclasses import dataclass

import pytest
from aws_lambda_powertools.event_handler import APIGatewayRestResolver


@pytest.fixture
def lambda_context():
    @dataclass
    class LambdaContext:
        function_name: str = "test"
        memory_limit_in_mb: int = 128
        invoked_function_arn: str = "arn:aws:lambda:eu-west-1:123456789012:function:test"
        aws_request_id: str = "da658bd3-2d6f-4e7b-8ec2-937234644fdc"

    return LambdaContext()


def test_api_gateway_plus_path_capturing(lambda_context):
    app = APIGatewayRestResolver()

    @app.get("/dummy/<value>")
    def handler(value: str):
        assert value == "a+b"
        return {}

    response = app.resolve(
        {
            "path": "/dummy/a+b",
            "httpMethod": "GET",
            "requestContext": {"requestId": "227b78aa-779d-47d4-a48e-ce62120393b8"}
        },
        lambda_context
    )

    assert response["statusCode"] == 200

Possible Solution

api_gateway.pyL44 contains definition of safe characters. This list is incomplete. By rfc3986 Section 3.3 path is built from segments where segments can contain sub-delims which are defined as:

sub-delims  = "!" / "$" / "&" / "'" / "(" / ")"
                  / "*" / "+" / "," / ";" / "="

API Gateway resolver is using this list of characters when building route regex:

_SAFE_URI = "-._~()'!*:@,;="

Plus sign (+), dollar sign ($) and ampersand sign (&) are missing from that list. Adding them would resolve this issue.

Steps to Reproduce

Run above code snippet as pytest test.

Powertools for AWS Lambda (Python) version

latest

AWS Lambda function runtime

3.10

Packaging format used

PyPi

Debugging logs

No response

[leandrodamascena]

Looking at this now.

[leandrodamascena]

Hello @nejcskofic! I can confirm that this is indeed a bug and we need to fix it. Our Resolver must be able to handle these additional characters: $/&.

Do you want to submit a fix + tests for this issue? We plan to launch a release on Friday and we'd love it if you would send in a PR to contribute to Powertools for AWS Lambda.

Don't worry if you can't, We know everyone's been very busy and I can fix that.

[nejcskofic]

Hello @leandrodamascena. Thanks for the response. I can take a look at it later today. One question though: in your response you mention only $ and &. What about + (which was my original issue)?

[leandrodamascena]

Sorry, I made a mistake! Yes, include + as well. 😑.

Thanks and let me know if you need any help.