Feature: Autoload submodules.

[ryan-roemer]

• [ ] Check if something like this already exists
• [ ] Figure out how to handle differing options.
• [ ] Consider how outputs of submodules work.
• [ ] Update doc examples to show both.
• [ ] Experiment if a map within a list can work or like a map of nested maps.

Idea:

module "serverless" {
  source = "FormidableLabs/serverless/aws"

  region       = "us-east-1"
  service_name = "sparklepants"
  stage        = "${var.stage}"

  modules = [
    "xray" # submodules/xray/
  ]

  plugins = [
    "serverless-s3-sync" # submodules/plugin-serverless-s3-sync/
  ]
}

[ryan-roemer]

Research

I’ve been trying to wrangle a seemingly simple idea: I want to conditionally include a sub-module based on a variable.

Things I’ve tried that failed:

count: Idea - set count to 0 if not using.

module "foo" {
  count  = "${var.use_foo ? 1 : 0}"
  source = "./modules/foo"
}

source: Idea - swap real submodule for a completely empty one.

module "foo" {
  source = "${var.use_foo ? "./modules/foo" : "./modules/empty"}"
}

[CumpsD]

These things seem related to this:

• https://github.com/hashicorp/terraform/issues/1439
• http://bensnape.com/2016/01/14/terraform-design-patterns-the-terrafile/

[ryan-roemer]

0.12 Update

module.count is now a reserved word. When implemented in the future, will presumably get us there. See https://www.hashicorp.com/blog/hashicorp-terraform-0-12-preview-for-and-for-each/#module-count-and-for_each

For a long time, users have wished to be able to use the count meta-argument within module blocks, allowing multiple instances of the same module to be created more easily.

Again, we have been laying the groundwork for this during Terraform 0.12 development and expect to complete this work in a later release. Along with count, module blocks will also accept the new for_each argument described for resources above, with similar results.

This feature is particularly complicated to implement within Terraform's existing architecture, so some more work will certainly be required before we can support this. To avoid further breaking changes in later releases, 0.12 will reserve the module input variable names count and for_each in preparation for the completion of this feature.