Support typed structs inside dynamic iterators

[a0s]

Not sure is it bug or feature

This is not working

const resolverEndpoint = new Route53ResolverEndpoint(this, "resolver_endpoint", <Route53ResolverEndpointConfig>{
      provider: config.provider,
      direction: "INBOUND",
      securityGroupIds: [this.resolverSecurityGroup.id],
      ipAddress: subnetIdsIterator.dynamic(<Route53ResolverEndpointIpAddress>{
        subnetId: subnetIdsIterator.key
      }),
      tags: {
        Name: "vpn-resolver"
      }
    })

│ Error: Extraneous JSON object property
│ 
│   on cdk.tf.json line 1859, in resource.aws_route53_resolver_endpoint.vpn_endpoint_resolver_endpoint_61EF1F6A.dynamic.ip_address.content:
│ 1859:               "subnetId": "${each.key}"
│ 
│ No argument or block type is named "subnetId". Did you mean "subnet_id"?
╵
╷
│ Error: Missing required argument
│ 
│   on cdk.tf.json line 1860, in resource.aws_route53_resolver_endpoint.vpn_endpoint_resolver_endpoint_61EF1F6A.dynamic.ip_address.content:
│ 1860:             },
│ 
│ The argument "subnet_id" is required, but no definition was found.

But this works ok (but my perfectionism suffers at this point due to the use of an untyped struct)

const resolverEndpoint = new Route53ResolverEndpoint(this, "resolver_endpoint", <Route53ResolverEndpointConfig>{
      provider: config.provider,
      direction: "INBOUND",
      securityGroupIds: [this.resolverSecurityGroup.id],
      ipAddress: subnetIdsIterator.dynamic({
        subnet_id: subnetIdsIterator.key
      }),
      tags: {
        Name: "vpn-resolver"
      }
    })

[ansgarm]

Hi @a0s 👋
Yeah, that is intentional at the moment, as we have no type information for the target attribute and we can't guess whether a key should be snake-case as it is part of Terraform config or whether it should stay as is because it may be part of unstructured data passed to e.g. a kubernetes spec.
We want to tackle this in the future (possibly in #1869 but that is currently more about the types of the "input").

If your example is safe enough to be snake cased everywhere, you could do something like this (untested, experimental, uses internal apis that could change):

import { keysToSnakeCase } from 'cdktf/lib/util';

const resolverEndpoint = new Route53ResolverEndpoint(this, "resolver_endpoint", <Route53ResolverEndpointConfig>{
      provider: config.provider,
      direction: "INBOUND",
      securityGroupIds: [this.resolverSecurityGroup.id],
      ipAddress: subnetIdsIterator.dynamic(keysToSnakeCase(<Route53ResolverEndpointIpAddress>{
        subnetId: subnetIdsIterator.key
      })),
      tags: {
        Name: "vpn-resolver"
      }
});

This only works in TypeScript and uses an utility function that CDKTF uses internally.

[a0s]

Thank you for response! This is an interesting trick.