Stack Dependencies

stack-dependencies — Cross-stack dependency support and autoinclude improvements

The stack-dependencies experiment now supports cross-stack and nested-stack dependency patterns, expanding the autoinclude block capabilities in terragrunt.stack.hcl files.

New features:

• stack.<name>.path references for depending on an entire stack. The DAG expands the stack into its constituent units so that all units in the stack complete before the dependent unit runs
• stack.<name>.<unit_name>.path references for depending on a specific unit within a nested stack (fine-grained cross-stack dependencies)
• dependency blocks targeting stack directories — aggregated outputs from all units in the stack are accessible as dependency.stack_name.outputs.unit_name.output_key
• Partial evaluation of local.* in autoinclude — expressions mixing local.* and dependency.* are partially evaluated during stack generation: locals resolve to literals while dependency references are preserved for evaluation when the unit is applied

Dependency on an entire stack:

stack "infra" {
  source = "../catalog/stacks/infra"
  path   = "infra"
}

unit "app" {
  source = "../catalog/units/app"
  path   = "app"

  autoinclude {
    dependency "infra" {
      config_path = stack.infra.path
    }

    inputs = {
      vpc_id = dependency.infra.outputs.vpc.vpc_id
    }
  }
}

Dependency on a unit within a nested stack:

stack "networking" {
  source = "../catalog/stacks/networking"
  path   = "networking"
}

unit "app" {
  source = "../catalog/units/app"
  path   = "app"

  autoinclude {
    dependency "vpc" {
      config_path = stack.networking.vpc.path
    }

    inputs = {
      vpc_id = dependency.vpc.outputs.vpc_id
    }
  }
}

terragrunt run --all --experiment stack-dependencies -- plan

To learn more, see the experiment documentation.