If I have the following astro config

---

modules:
  - name: foo
    path: ./foo 
    remote:
      backend: local
      backend_config:
        path: /tmp/terraform-tests/foo.tfstate

  - name: bar
    path: ./bar
    remote:
      backend: local
      backend_config:
        path: /tmp/terraform-tests/bar.tfstate
    variables:
      - name: region

and run astro plan --region us-west-1 I'll get an error in Terraform 0.12 saying Error: Value for undeclared variable, because region variables will be passed to the foo module that doesn't declare it.

This is related to hashicorp/terraform#19424. Passing undeclared variables through -var arguments is no longer allowed in Terraform 0.12.