variable/expression references in module source attribute

[jan-g]

Terraform Version

All

Use Cases

I'm interested in deployments across multiple cloud providers. By-and-large the TF for these are the same, with some features varying.

I'm particularly interested in being able to write multiple modules that conform to the same interface, with implementations selected on the basis of a variable value.

Attempted Solutions

This is not something that can currently be done within terraform.

Proposal

It'd be great if this would work:

# main.tf
variable "platform" {
  type = string
  default = "p1"
}

module "m" {
  source = "./module/${var.platform}"
  x = 10
}

output "y" {
  value = module.m.y
}

# module/p1/main.tf
variable "x" {
  type = number
}

output "y" {
  value = var.x + 1
}

# module/p2/main.tf
variable "x" {
  type = number
}

output "y" {
  value = var.x * 2
}

I'd be happy with variables / expressions computed from locally-available values (eg, selecting the module to use from a yaml config file).

References

• terraform get: can't use variable in module source parameter? #1439 kind of tapered off. The "fix" was to change an error message. It'd be great to revisit this.

[crw]

Thanks for this feature request! If you are viewing this issue and would like to indicate your interest, please use the 👍 reaction on the issue description to upvote this issue. We also welcome additional use case descriptions. Thanks again!