Formatting can change code semantics for literal strings

[NiklasRosenstein]

The following code:

  dynamic "rule" {
    for_each = concat(local.default_firewall_rules.open_tcp_ports, var.extra_firewall_rules.open_tcp_ports)
    content {
      direction  = "in"
      protocol   = "tcp"
      port       = "${rule.value}"
      source_ips = ["0.0.0.0/0"]
    }
  }

Is formatted to the following by the plugin:

  dynamic "rule" {
    for_each = concat(local.default_firewall_rules.open_tcp_ports, var.extra_firewall_rules.open_tcp_ports)
    content {
      direction  = "in"
      protocol   = "tcp"
      port       = rule.value
      source_ips = ["0.0.0.0/0"]
    }
  }

Note that "${rule.value}" got unpacked into just rule.value. The resulting code however has different semantics as here it is intended to be used as an alternative for tostring().

Arguments made that one should use tostrings() instead, but it is fundamentally important property of a formatter to not change the semantics of the code.

If one would want such a change to be done automatically in some fashion, it would be a linter's job, behind an --unsafe-fixes (or vice-versa) option.