update existing infrastructure on heroku using terraform - heroku

Question

I've got this infrastructure description
variable "HEROKU_API_KEY" {}
provider "heroku" {
email = "sebastrident#gmail.com"
api_key = "${var.HEROKU_API_KEY}"
}
resource "heroku_app" "default" {
name = "judge-re"
region = "us"
}
Originally I forgot to specify buildpack. It created the application on heroku. I decided to add it to resource entry
buildpacks = [
"heroku/java"
]
But when I try to apply the plan in terraform I get this error
Error: Error applying plan:
1 error(s) occurred:
* heroku_app.default: 1 error(s) occurred:
* heroku_app.default: Post https://api.heroku.com/apps: Name is already taken
Terraform does not automatically rollback in the face of errors.
Instead, your Terraform state file has been partially updated with
any resources that successfully completed. Please address the error
above and apply again to incrementally change your infrastructure.
Terraform plan looks like this
Refreshing Terraform state in-memory prior to plan...
The refreshed state will be used to calculate this plan, but will not be
persisted to local or remote state storage.
------------------------------------------------------------------------
An execution plan has been generated and is shown below.
Resource actions are indicated with the following symbols:
+ create
Terraform will perform the following actions:
+ heroku_app.judge_re
id: <computed>
all_config_vars.%: <computed>
buildpacks.#: "1"
buildpacks.0: "heroku/java"
config_vars.#: <computed>
git_url: <computed>
heroku_hostname: <computed>
name: "judge-re"
region: "us"
stack: <computed>
web_url: <computed>
Plan: 1 to add, 0 to change, 0 to destroy.
------------------------------------------------------------------------
Note: You didn't specify an "-out" parameter to save this plan, so Terraform
can't guarantee that exactly these actions will be performed if
"terraform apply" is subsequently run.
As a workaround I tried to add destroy in my deploy.sh script
terraform init
terraform plan
terraform destroy -force
terraform apply -auto-approve
But it does not destroy the resource as I get the message Destroy complete! Resources: 0 destroyed.
What is the problem?
Link to build

Answer 1

It looks like you also changed the name of the resource. Your original example has the resource name heroku_app.default while your plan has heroku_app.judge_re.
To point your state to the remote resource, so Terraform knows you are editing and not trying to recreate the resource, use terraform import:
terraform import heroku_app.judge_re judge-re

Answer 2

In terraform, normally you needn't destroy the whole stack, which you just want to re-build one or several resources in it.
terraform taint does this trick. The terraform taint command manually marks a Terraform-managed resource as tainted, forcing it to be destroyed and recreated on the next apply.
terraform taint heroku_app.default
Second, when you troubleshooting why the resource isn't list in destroy resource, please make sure you point to the right terraform tfstate file.
when you run terraform plan, did you see any resources which already was created?