(ec2): Subnet and ISubnet variable naming causes Pylance type error

[jakestambaugh]

Describe the bug

The L2 construct Subnet doesn't use the same method parameter names as ISubnet in associate_network_acl. This makes Pylance believe that Subnet does not implement the interface ISubnet, causing it to raise warnings.

Expected Behavior

Pylance would understand that "Subnet" implements "ISubnet" and not raise errors.

Current Behavior

(variable) subnet: Subnet
Argument of type "list[Subnet]" cannot be assigned to parameter "subnets" of type "Sequence[ISubnet] | None" in function "__init__"
  Type "list[Subnet]" cannot be assigned to type "Sequence[ISubnet] | None"
    TypeVar "_T_co@Sequence" is covariant
      "Subnet" is incompatible with protocol "ISubnet"
        "associate_network_acl" is an incompatible type
          Type "(id: str, network_acl: INetworkAcl) -> None" cannot be assigned to type "(id: str, acl: INetworkAcl) -> None"

Reproduction Steps

In VS Code with the "Pylance" language server extension enabled, add this stack to a CDK project and look for the red squiggly lines in the SubnetSelection constructor.

from aws_cdk import (
    # Duration,
    Stack,
    aws_ec2 as ec2,
)
from constructs import Construct


class ReproStack(Stack):
    def __init__(self, scope: Construct, construct_id: str, **kwargs) -> None:
        super().__init__(scope, construct_id, **kwargs)

        vpc = ec2.Vpc(self, "vpc")
        subnet = ec2.Subnet(
            self,
            "subnet",
            availability_zone="us-east-1a",
            vpc_id=vpc.vpc_id,
            cidr_block="10.0.0.0/16",
        )

        subnet_filter = ec2.SubnetSelection(subnets=[subnet])

Possible Solution

Change the parameter name for the INetworkAcl type to be consistent across Subnet and ISubnet.

aws-cdk/packages/@aws-cdk/aws-ec2/lib/vpc.ts

Line 61 in f199fad

associateNetworkAcl(id: string, acl: INetworkAcl): void;

aws-cdk/packages/@aws-cdk/aws-ec2/lib/vpc.ts

Line 1757 in f199fad

public associateNetworkAcl(id: string, networkAcl: INetworkAcl) {

Additional Information/Context

No response

CDK CLI Version

2.22.0 (build 1db4b16)

Framework Version

Pylance v2022.4.3

Node.js Version

v16.14.2

OS

Ubuntu 20.04.4 LTS (WSL 2)

Language

Python

Language Version

3.10.4

Other information

No response

[corymhall]

@jakestambaugh I was not able to reproduce this issue. I created a new project with

npx cdk init --language=python app

I then opened VSCode and installed the
Pylance extension
and used the code that you provided in the description.

Is there anything else about your setup that could be causing the issue?

[jakestambaugh]

I think that I installed Pylance as a dependency of the "Python" package (https://marketplace.visualstudio.com/items?itemName=ms-python.python). It could be that the default Pylance extension settings don't configure linting.

FWIW, I was able to reproduce this on a fresh Ubuntu installation with the Python extension.

If you want to add this to the .vscode/extensions.json file it will suggest the Python plugin:

{
    "recommendations": [
        "ms-python.python"
    ]
}

[gshpychka]

This happens in a lot of constructs and is being tracked here: aws/jsii#4541 and aws/jsii#2927

[skalinets]

Are there any workarounds available? Like muting pyright warnings etc. The issues from previous comment are more than one year old :) Just wondering how people work with python CDK.

[gshpychka]

Are there any workarounds available? Like muting pyright warnings etc. The issues from previous comment are more than one year old :) Just wondering how people work with python CDK.

yes, the current workaround is to use typing.cast to satisfy the type checker.

[MrArnoldPalmer]

Closing this as a duplicate of aws/jsii#4541 track there for updates/comments.

[github-actions]

⚠️COMMENT VISIBILITY WARNING⚠️

Comments on closed issues are hard for our team to see.
If you need more assistance, please either tag a team member or open a new issue that references this one.
If you wish to keep having a conversation with other community members under this issue feel free to do so.