Report on mutually-exclusive count and for_each attributes

[dbanck]

Context

While it's possible to declare count and for_each in a resource (and other) block, the configuration is not valid. We can catch this early in the enhanced validation.

resource "aws_instance" "name" {
  for_each = {
    "key" = "value"
  }
  count = 3
}

Trying to run the above configuration does not work. terraform validate will report this as an error:

╷
│ Error: Invalid combination of "count" and "for_each"
│ 
│   on main.tf line 25, in resource "aws_instance" "name":
│   25:   for_each = {
│ 
│ The "count" and "for_each" meta-arguments are mutually-exclusive, only one should be used to be explicit about the number of resources to be created.
╵

Proposal

• Add a new validator in terraform-ls that checks if both attributes are present and raises a diagnostic