How to add api-key to google secret-manager - google-cloud-platform

Question

With Terraform GCP provider 4.30.0, I can now create an google maps api key and restrict it.
resource "google_apikeys_key" "maps-api-key" {
provider = google-beta
name = "maps-api-key"
display_name = "google-maps-api-key"
project = local.project_id
restrictions {
api_targets {
service = "static-maps-backend.googleapis.com"
}
api_targets {
service = "maps-backend.googleapis.com"
}
api_targets {
service = "places-backend.googleapis.com"
}
browser_key_restrictions {
allowed_referrers = [
"https://${local.project_id}.ey.r.appspot.com/*", # raw url to the app engine service
"*.example.com/*" # Custom DNS name to access to the app
]
}
}
}
The key is created and appears in the console as expected and I can see the API_KEY value.
When I deploy my app, I want it to read the API_KEY string.
My node.js app already reads secrets from secret manager, so I want to add it as a secret.
Another approach could be for the node client library to read the API credential directly, instead of using secret-manager, but I haven't found a way to do that.
I can't work out how to read the key string and store it in the secret.
The terraform resource describes the output
key_string - Output only. An encrypted and signed value held by this
key. This field can be accessed only through the GetKeyString method.
I don't know how to call this method in Terraform, to pass the value to a secret version.
This doesn't work.
v1 = { enabled = true, data = resource.google_apikeys_key.maps-api-key.GetKeyString }

Answer 1

Referencing attributes and arguments does not work the way you tried it. You did quote the correct attribute though, but just failed to specify it:
v1 = {
enabled = true,
data = resource.google_apikeys_key.maps-api-key.key_string
}
Make sure to understand how referencing attributes in Terraform works [1].
[1] https://www.terraform.io/language/expressions/references#references-to-resource-attributes