Implement block-level iterators

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Description

To support dynamic list iterations on the block / resource level we will introduce a new API, called Iterator.

In this issue we are building the block-level Iterator API. To create dynamic blocks one can use iterator.dynamic([…]) and the block will be repeated for each item in the list.

import { TerraformStack, Iterator } from "cdktf";
import { S3Bucket, DataAwsSubnets, DataAwsAllowedOrigins } from "./.gen/providers/aws-ficticious";
import { Construct } from "constructs";

export class MyStack extends TerraformStack {
 constructor(scope: Construct, id: string) {
   super(scope, id);

  // Fictitious data source that returns [{method, origin}]
   const allowedOrigins = new DataAwsAllowedOrigins(
     this,
     "possibleOrigins",
     {}
   );
   const allowedOriginsIterator = Iterator.fromList(allowedOrigins.origins);
   new S3Bucket(this, "my-bucket", {
     corsRule: allowedOriginsIterator.dynamic(
       {
         allowedMethods: [allowedOriginsIterator.getStringProperty("method")],
         allowedOrigins: [allowedOriginsIterator.getStringProperty("origin")],
         maxAgeSeconds: 42,
       },
     ),
   });
 }
}

References

• Part of #1094
• Depends on #1797

[ansgarm]

Hi @RichiCoder1, yeah, I thought about that, too. However, as we’re constrained by JSII (which translates our TypeScript bindings to the other languages we support), we can’t directly use callbacks, but rather need to pass what would for example be the equivalent of an anonymous inner class in Java. So it would need to look like this:

new S3Bucket(this, "my-bucket", {
  corsRule: allowedOriginsIterator.forEach(
    { callback: it =>
      {
        allowedMethods: [it.getStringProperty("method")],
        allowedOrigins: [it.getStringProperty("origin")],
        maxAgeSeconds: 42,
        someOtherAttribute: index++
      },
    }
  ),
});

I’m unsure whether this would still simplify things compared to .dynamic({ ... }) or even .forEach({ ... }).

[RichiCoder1]

@ansgarm that’s fair, JSII strikes again. dynamic seems fine then, considering constraints