Terraform child module does not inherit provider from root module - terraform

Question

My problem
I am having trouble defining the provider for my module.
Terraform fails to find the provider's plugin when I run terraform init and it shows the wrong provider for my module when I run terraform providers.
Setup
I am using Terraform version 1.3.7 on Debian 11.
Here's an example of what I am trying to do.
I have a main.tf where is my main configuration and modules. In this example I use a single module for creating a docker container.
.
├── main.tf
└── modules/
└── container_module/
└── main.tf
In the root module project/main.tf file, I define the provider and call the module:
terraform {
required_providers {
docker = {
source = "kreuzwerker/docker"
version = "3.0.1"
}
}
}
provider "docker" {
host = "unix:///var/run/docker.sock"
}
module "container" {
source = "./modules/container_module"
}
In the modules/container_module/main.tf, I create the docker container resource:
resource "docker_image" "debian" {
name = "debian:latest"
}
resource "docker_container" "foo" {
image = docker_image.debian.image_id
name = "foo"
}
What I expect to happen
When I run terraform init, it should download the provider's plugin from kreuzwerker/docker.
What actually happens
Instead, terraform downloads the plugin from kreuzwerker/docker once, then attempt to download it again from hashicorp/docker.
Here's the command's output:
terraform init
Initializing modules...
- container in modules/container_module
Initializing the backend...
Initializing provider plugins...
- Finding latest version of hashicorp/docker...
- Finding kreuzwerker/docker versions matching "3.0.1"...
- Installing kreuzwerker/docker v3.0.1...
- Installed kreuzwerker/docker v3.0.1 (self-signed, key ID BD080C4571C6104C)
Partner and community providers are signed by their developers.
If you'd like to know more about provider signing, you can read about it here:
https://www.terraform.io/docs/cli/plugins/signing.html
╷
│ Error: Failed to query available provider packages
│
│ Could not retrieve the list of available versions for provider hashicorp/docker: provider registry registry.terraform.io does not have a provider named
│ registry.terraform.io/hashicorp/docker
│
│ Did you intend to use kreuzwerker/docker? If so, you must specify that source address in each module which requires that provider. To see which modules are currently depending on
│ hashicorp/docker, run the following command:
│ terraform providers
╵
When I run terraform providers I get two different sources depending on the file:
terraform providers
Providers required by configuration:
.
├── provider[registry.terraform.io/kreuzwerker/docker] 3.0.1
└── module.container
└── provider[registry.terraform.io/hashicorp/docker]
According to the documentation, the child modules should inherit the provider from their parent:
Default Behavior: Inherit Default Providers:
If the child module does not declare any configuration aliases, the providers argument is optional. If you omit it, a child module inherits all of the default provider configurations from its parent module. (Default provider configurations are ones that don't use the alias argument.)
I have already checked this
Do terraform modules need required_providers?
This answer confirms the provider inheritence.
Terraform provider's resources not available in other tf files:
This question didn't help.
Terraform, providers miss inherits on module
This answer to this similar question says that I should add required_providers in the child module, but it is for an older version and it contradicts what I saw elsewhere.
I have the same issue when I create a providers.tf file in the root directory.
My question
How should I declare my provider so that the child module can inherit the provider from the root module?

Answer 1

kreuzwerker/docker is not a hashicorp provider. Thus as explained here, you have to explicitly define required_providers in each module, as such providers are not inherited.