Where descriptions for variables and outputs spans multiple lines. The description MAY provide variable input examples for each variable using the HEREDOC format and embedded markdown.

Example:

variable "my_complex_input" {
  type = map(object({
    param1 = string
    param2 = optional(number, null)
  }))
  description = <<DESCRIPTION
A complex input variable that is a map of objects.
Each object has two attributes:

- `param1`: A required string parameter.
- `param2`: (Optional) An optional number parameter.

Example Input:

```terraform
my_complex_input = {
  "object1" = {
    param1 = "value1"
    param2 = 2
  }
  "object2" = {
    param1 = "value2"
  }
}
```
DESCRIPTION
}

The ignore_changes attribute MUST NOT be enclosed in double quotes.

Good example:

lifecycle {
    ignore_changes = [
      tags,
    ]
}

Bad example:

Sometimes we need to ensure that the resources created are compliant to some rules at a minimum extent, for example a subnet has to be connected to at least one network_security_group. The user SHOULD pass in a security_group_id and ask us to make a connection to an existing security_group, or want us to create a new security group.

An example from the community:

resource "azurerm_kubernetes_cluster" "main" {
  ...
  dynamic "identity" {
    for_each = var.client_id == "" || var.client_secret == "" ? [1] : []

    content {
      type                      = var.identity_type
      user_assigned_identity_id = var.user_assigned_identity_id
    }
  }
  ...
}

Please refer to the coding style in the example. Nested blocks under conditions, MUST be declared as:

The following example shows how "${var.subnet_name}-nsg" SHOULD be used when var.new_network_security_group_name is null or ""

Good examples:

coalesce(var.new_network_security_group_name, "${var.subnet_name}-nsg")

try(coalesce(var.new_network_security_group.name, "${var.subnet_name}-nsg"), "${var.subnet_name}-nsg")

Bad examples:

var.new_network_security_group_name == null ? "${var.subnet_name}-nsg" : var.new_network_security_group_name)

Since Terraform 0.13, count, for_each and depends_on are introduced for modules, module development is significantly simplified. Module’s owners MUST NOT add variables like enabled or module_depends_on to control the entire module’s operation. Boolean feature toggles are acceptable however.

Input variables SHOULD follow this order:

1. All required fields, in alphabetical order
2. All optional fields, in alphabetical order

A variable without default value is a required field, otherwise it’s an optional one.

The naming of a variable SHOULD follow HashiCorp’s naming rule .

variable used as feature switches SHOULD apply a positive statement, use xxx_enabled instead of xxx_disabled. Avoid double negatives like !xxx_disabled.

The target audience of description is the module users.

For a newly created variable (Eg. variable for switching dynamic block on-off), it’s description SHOULD precisely describe the input parameter’s purpose and the expected data type. description SHOULD NOT contain any information for module developers, this kind of information can only exist in code comments.

type MUST be defined for every variable. type SHOULD be as precise as possible, any MAY only be defined with adequate reasons.

• Use bool instead of string or number for true/false
• Use string for text
• Use concrete object instead of map(any)