Aws-cdk: Unused route table created when creating a subnet

[Kent1]

• I'm submitting a ...

  • [x] :beetle: bug report
  • [ ] :rocket: feature request
  • [ ] :books: construct library gap
  • [ ] :phone: security issue or vulnerability => Please see policy
  • [ ] :question: support request => Please see note at the top of this template.

• What is the current behavior?
  When i create a Subnet, and change the RouteTableAssociation to an existing route table, an unused route table is created along with the subnet.

• What is the expected behavior (or behavior of feature suggested)?
  I would like to be able to remove this route table or that cdk is smart enough to not create it

• Please tell us about your environment:

  • CDK CLI Version: 1.3.0
  • Module Version: 1.3.0
  • OS: [OSX Mojave]
  • Language: [Java]

• Other information (e.g. detailed explanation, stacktraces, related issues, suggestions how to fix, links for us to have context, eg. associated pull-request, stackoverflow, gitter, etc)

Subnet Subnet = new Subnet(this, "Subnet", SubnetProps.builder()
        .withVpcId(vpc.getVpcId())
        .withAvailabilityZone("eu-west-1b")
        .withCidrBlock(String.format("10.%d.43.128/25", environmentId))
        .build());

CfnSubnetRouteTableAssociation routeTableAssociation = (CfnSubnetRouteTableAssociation) subnet.getNode().tryFindChild("RouteTableAssociation");
routeTableAssociation.setRouteTableId(Fn.importValue(String.format("%s-nat-nat000", environment)));

CfnRouteTable cfnRouteTable = (CfnRouteTable) subnet.getNode().tryFindChild("RouteTable");

[rix0rrr]

I'm not sure this counts as a bug.

Unfortunately, the Subnet construct right now is heavily tied to the Vpc construct, and supports exactly the features it needs.

This sounds like a feature request for an optional RouteTable input parameter to Subnet.

[konstantinj]

4308 RouteTable input would be appreciated.

Not only in SubnetProps but also in subnetConfiguration so it can be used directly in the VPC construct.

[rix0rrr]

Related to https://github.com/aws/aws-cdk/issues/5927