elasticloadbalancingv2:Cannot construct AlbListenerTarget using lookUp

[gratinierer]

Describe the bug

Constructing AlbListenerTarget with Listener fromLookup fails:

alb = aws_cdk.aws_elasticloadbalancingv2.ApplicationLoadBalancer.from_lookup(
            self,
            'ApplicationBalancer',
            load_balancer_tags={
                'elasticbeanstalk:environment-name': 'myenv'})
logging.info(f'found alb with arn <{alb.load_balancer_arn}>')
aws_elasticloadbalancingv2_targets.AlbTarget(alb=alb, port=80) 
listener = ApplicationListener.from_lookup(self, 'ApplicationListener',
                                                   load_balancer_arn=alb.load_balancer_arn, listener_port=80)
logging.info(f'found listener with arn <{listener.listener_arn}>')
alb_target = aws_elasticloadbalancingv2_targets.AlbListenerTarget(listener)

==>

2025-01-29 05:32:38 INFO     found alb with arn <arn:aws:elasticloadbalancing:us-west-2:123456789012:loadbalancer/application/my-load-balancer/50dc6c495c0c9188>
2025-01-29 05:32:38 INFO     found listener with arn <arn:aws:elasticloadbalancing:us-west-2:123456789012:listener/application/my-load-balancer/50dc6c495c0c9188/f2f7dc8efc522ab2>
(....)py", line 62, in get_alb_listener
    alb_target = aws_elasticloadbalancingv2_targets.AlbListenerTarget(listener)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/root/.pyenv/versions/3.11.11/lib/python3.11/site-packages/jsii/_runtime.py", line 118, in __call__
    inst = super(JSIIMeta, cast(JSIIMeta, cls)).__call__(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/root/.pyenv/versions/3.11.11/lib/python3.11/site-packages/aws_cdk/aws_elasticloadbalancingv2_targets/__init__.py", line 157, in __init__
    check_type(argname="argument alb_listener", value=alb_listener, expected_type=type_hints["alb_listener"])
  File "/root/.pyenv/versions/3.11.11/lib/python3.11/site-packages/aws_cdk/aws_elasticloadbalancingv2_targets/__init__.py", line 25, in check_type
    return typeguard.check_type(argname=argname, value=value, expected_type=expected_type) # type:ignore
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/root/.pyenv/versions/3.11.11/lib/python3.11/site-packages/typeguard/__init__.py", line 785, in check_type
    raise TypeError(
TypeError: type of argument alb_listener must be aws_cdk.aws_elasticloadbalancingv2.ApplicationListener; got jsii._reference_map.InterfaceDynamicProxy instead

Regression Issue

• Select this option if this issue appears to be a regression.

Last Known Working CDK Version

No response

Expected Behavior

it should be possible to construct the listener.

Current Behavior

cosntruction fails due to type-problems.

Reproduction Steps

it should be possible to reproduce with the code above.
we have to switch wo AlbListenerTarget because of deprecation of AlbTarget.
As you can see in the code AlbTarget works (in production here) fine with the 'ApplicationLoadBalancer.from_lookup', so the ALB and also the listeners are in place.

Possible Solution

No response

Additional Information/Context

No response

CDK CLI Version

2.166.0

Framework Version

No response

Node.js Version

20.15.0

OS

Linux

Language

Python

Language Version

No response

Other information

No response

[pahud]

reproducible in 2.177.0

from aws_cdk import (
    Stack,
    aws_ec2 as ec2,
    aws_elasticloadbalancingv2 as elbv2,
    aws_elasticloadbalancingv2_targets as elbv2_targets,
)
from constructs import Construct
import logging

class IssueTriagePyStack(Stack):

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

        # Get the default VPC
        vpc = ec2.Vpc.from_lookup(self, "VPC", is_default=True)

        # Create Application Load Balancer
        alb = elbv2.ApplicationLoadBalancer(
            self, "MyALB",
            vpc=vpc,
            internet_facing=True
        )

        # Create Target Group
        target_group = elbv2.ApplicationTargetGroup(
            self, "MyTargetGroup",
            vpc=vpc,
            port=80,
            protocol=elbv2.ApplicationProtocol.HTTP,
            target_type=elbv2.TargetType.INSTANCE
        )

        # Add Listener
        listener = alb.add_listener(
            "MyListener",
            port=80,
            default_target_groups=[target_group]
        )

        # add import statements below
        alb = elbv2.ApplicationLoadBalancer.from_lookup(
            self, 'ApplicationBalancer',
            load_balancer_tags={'elasticbeanstalk:environment-name': 'myenv'}
        )
        logging.info(f'found alb with arn <{alb.load_balancer_arn}>')

        elbv2_targets.AlbTarget(alb=alb, port=80)

        listener = elbv2.ApplicationListener.from_lookup(
            self, 'ApplicationListener',
            load_balancer_arn=alb.load_balancer_arn,
            listener_port=80
        )
        logging.info(f'found listener with arn <{listener.listener_arn}>')

        alb_target = elbv2_targets.AlbListenerTarget(listener)

% cdk diff
[WARNING] aws-cdk-lib.aws_elasticloadbalancingv2_targets.AlbTarget is deprecated.
  Use `AlbListenerTarget` instead or
`AlbArnTarget` for an imported load balancer. This target does not automatically
add a dependency between the ALB listener and resulting NLB target group,
without which may cause stack deployments to fail if the NLB target group is provisioned
before the listener has been fully created.
  This API will be removed in the next major release.
Traceback (most recent call last):
  File "/Users/hunhsieh/repos/issue-triage-py/app.py", line 10, in <module>
    IssueTriagePyStack(app, "IssueTriagePyStack",
    ~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^
        # If you don't specify 'env', this stack will be environment-agnostic.
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    ...<13 lines>...
        # For more information, see https://docs.aws.amazon.com/cdk/latest/guide/environments.html
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        )
        ^
  File "/Users/hunhsieh/repos/issue-triage-py/.venv/lib/python3.13/site-packages/jsii/_runtime.py", line 118, in __call__
    inst = super(JSIIMeta, cast(JSIIMeta, cls)).__call__(*args, **kwargs)
  File "/Users/hunhsieh/repos/issue-triage-py/issue_triage_py/issue_triage_py_stack.py", line 57, in __init__
    alb_target = elbv2_targets.AlbListenerTarget(listener)
  File "/Users/hunhsieh/repos/issue-triage-py/.venv/lib/python3.13/site-packages/jsii/_runtime.py", line 118, in __call__
    inst = super(JSIIMeta, cast(JSIIMeta, cls)).__call__(*args, **kwargs)
  File "/Users/hunhsieh/repos/issue-triage-py/.venv/lib/python3.13/site-packages/aws_cdk/aws_elasticloadbalancingv2_targets/__init__.py", line 157, in __init__
    check_type(argname="argument alb_listener", value=alb_listener, expected_type=type_hints["alb_listener"])
    ~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/hunhsieh/repos/issue-triage-py/.venv/lib/python3.13/site-packages/aws_cdk/aws_elasticloadbalancingv2_targets/__init__.py", line 25, in check_type
    return typeguard.check_type(argname=argname, value=value, expected_type=expected_type) # type:ignore
           ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/hunhsieh/repos/issue-triage-py/.venv/lib/python3.13/site-packages/typeguard/__init__.py", line 785, in check_type
    raise TypeError(
        'type of {} must be {}; got {} instead'.
        format(argname, qualified_name(expected_type), qualified_name(value)))
TypeError: type of argument alb_listener must be aws_cdk.aws_elasticloadbalancingv2.ApplicationListener; got jsii._reference_map.InterfaceDynamicProxy instead
Subprocess exited with error 1

I'll check if this issue exists in TS later.

[pahud]

OK I see the gap here.

If we check the TS doc, AlbListenerTarget requires a ApplicationListener typed argument while elbv2.ApplicationListener.fromLookup() essentially returns the interface, not a concrete ApplicationListener. I can see this error in TypeScript

Now, looking at CDK in python on AlbListenerTarget, it requires

Parameters
:
alb_listener (ApplicationListener) – The application load balancer listener to target.

but if you check the from_lookup method:

Return type
:
IApplicationListener

So I think you can't simply create an AlbListenerTarget() using an imported listener like that.

[gratinierer]

Thanks for checking, pahud.
It may be technically true, that I can‘t do that at the moment, but with the deprecation of AlbTaget we will be forced to use AlbListenerTarget to keep our code running.
What would be the migation-path for that?