Am I trying to do something that is not possible?

https://www.pulumi.com/docs/intro/concepts/resources/options/transformations/ You probably want to check

args.type

is a type that can have tags, and you need to manually merge the existing properties with the new ones, the transform doesn't do that automatically.

looking at this now, looks like this is what I need right? https://www.pulumi.com/blog/automatically-enforcing-aws-resource-tagging-policies/#automatically-applying-tags

yup full codes at https://github.com/joeduffy/aws-tags-example/tree/master/autotag-ts

then, is it need to maintain that taggableresourcetypes array?

yeh I don't think there's any way to work that automatically at the moment

what if I'm sure that all resources that I'm using supports tags? I can skip that if taggable, right?

Yeh probably

works well, I ended doing this

const notTaggable = [
  "aws:iam/rolePolicyAttachment:RolePolicyAttachment",
  "aws:ec2/securityGroupRule:SecurityGroupRule",
  "aws:ec2/routeTableAssociation:RouteTableAssociation",
];