(ec2.Vpc): Vpc.fromLookup should throw if subnet group name tag is explicitly given and does not exist

[1oglop1]

I suspect this may be a bug or I'm missing something.

I have an existing VPC with 6 subnets with a tag subnet_tier

AZ1	AZ2	TAG: subnet_tier
public_subnet_1	public_subnet_2	public
private_subnet_1	private_subnet_2	private
data_subnet_1	data_subnet_2	data

From my understanding of Vpc.from_lookup I can supply subnet_group_name_tag will assign the subnets to the correct group inside cdk.context.json
So I can then create a SubnetSelection expected by multiple resources (eg. Function)
So when I add following code in my stack I get an error.

vpc = Vpc.from_lookup(
                self,
                "VPC",
                vpc_id="vpc-123456",
                subnet_group_name_tag="subnet_tier",
            )
subnets = vpc.select_subnets(subnet_group_name='data').subnets

PythonFunction(
    self,
    "Function",
    ...
    vpc=vpc,
    vpc_subnets=subnets
)

Actual result

cdk.context.json is created with SubnetGroups

"subnetGroups": [
      {
        "name": "Private",
        "type": "Private",
       },
             {
        "name": "public",
        "type": "Public",
        }
]

Error message raised:

jsii.errors.JSIIError: You cannot reference a Subnet's availability zone if it was not supplied. Add the availabilityZone when importing using Subnet.fromSubnetAttributes()

Expected result

"subnetGroups": [
      {
        "name": "private",
        "type": "Private",
       },
      {
        "name": "data",
        "type": "Private",
       },
            {
        "name": "public",
        "type": "Public",
        }
]

No errors.

Environment

• CDK CLI Version: 1.96.0 (build 39f3df8)
• Module Version: ec2
• Node.js Version: N/A python CDK 1.96.0
• OS: macOS
• Language (Version): Python (3.8.6)

[rix0rrr]

subnets = vpc.select_subnets(subnet_group_name='data').subnets

PythonFunction(
    self,
    "Function",
    ...
    vpc=vpc,
    vpc_subnets=SubnetSelection(
        subnets=subnets
    )
)

This code does duplicate work. I wonder if not doing duplicate work will fix it:

PythonFunction(
    self,
    "Function",
    ...
    vpc=vpc,
    vpc_subnets=SubnetSelection(
        subnet_group_name='data'
    )
)

[1oglop1]

@rix0rrr Sorry I made a typo in vpc_subnets=... I tried many variations to make it work.
On top of that I found out that the tags were not properly assigned to all subnets.
data and private had tag subnet-tier while public had subnet_tier.
However I still think there is an undesired behaviour:

I supplied the wrong tag the context was created with Private and Public subnets. And I got error that data subnet is not there instead I'd expect error that tag subnet-tier does not exist

Also this is very confusing:

ec2.SubnetSelection vs ec2.SelectedSubnets

I also updated to 1.97.0 and can confirm it now works as expected!
You can close the issue unless you find it relevant to investigate my report of undesired behaviour

[rix0rrr]

SelectedSubnets is what you get from doing a SubnetSelection.

[github-actions]

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