Error: Inconsistent dependency lock file when extract resource into a module - terraform

Question

I am new to terraform and as I extracted one of the resources into a module I got this:
Error: Inconsistent dependency lock file
│
│ The following dependency selections recorded in the lock file are inconsistent with the current
│ configuration:
│ - provider registry.terraform.io/hashicorp/heroku: required by this configuration but no version is selected
│
│ To update the locked dependency selections to match a changed configuration, run:
│ terraform init -upgrade
How I did?
First I had this:
provider "heroku" {}
resource "heroku_app" "example" {
name = "learn-terraform-heroku-ob"
region = "us"
}
resource "heroku_addon" "redis" {
app = heroku_app.example.id
plan = "rediscloud:30"
}
after that terraform init was runing without error also terraform plan was successfull.
Then I extracted the redis resource declaration into a module:
provider "heroku" {}
resource "heroku_app" "example" {
name = "learn-terraform-heroku-ob"
region = "us"
}
module "key-value-store" {
source = "./modules/key-value-store"
app = heroku_app.example.id
plan = "30"
}
And the content of modules/key-value-store/main.tf is this:
terraform {
required_providers {
mycloud = {
source = "heroku/heroku"
version = "~> 4.6"
}
}
}
resource "heroku_addon" "redis" {
app = var.app
plan = "rediscloud:${var.plan}"
}
terraform get went well. but terraform plan showed me the above error!

Answer 1

For this code to work, you have to have the required_providers blocks in both the root and child modules. So, the following needs to happen:
Add the required_providers block to the root module (this is what you have already)
Add the required_providers block to the child module and name it properly (currently you have set it to mycloud, and provider "heroku" {} block is missing)
The code that needs to be added in the root module is:
terraform {
required_providers {
heroku = {
source = "heroku/heroku"
version = "~> 4.6"
}
}
}
provider "heroku" {}
resource "heroku_app" "example" {
name = "learn-terraform-heroku-ob"
region = "us"
}
module "key-value-store" {
source = "./modules/key-value-store"
app = heroku_app.example.id
plan = "30"
}
In the child module (i.e., ./modules/key-value-store) the following needs to be present:
terraform {
required_providers {
heroku = { ### not mycloud
source = "heroku/heroku"
version = "~> 4.6"
}
}
}
provider "heroku" {} ### this was missing as well
resource "heroku_addon" "redis" {
app = var.app
plan = "rediscloud:${var.plan}"
}
This stopped working when the second resource was moved to the module as Heroku is not an official Terraform provider hence the provider settings are not propagated to the modules. For the unofficial providers (e.g., marked with verified), corresponding blocks of required_providers and provider <name> {} have to be defined. Also, make sure to remove the .terraform directory and re-run terraform init.