* Module variable type constraints now support an `optional()` modifier for object attribute types. Optional attributes may be omitted from the variable value, and will be replaced by a default value (or `null` if no default is specified). For example:
```terraform
variable "with_optional_attribute" {
type = object({
a = string # a required attribute
b = optional(string) # an optional attribute
c = optional(number, 127) # an optional attribute with default value
})
}
```
Assigning `{ a = "foo" }` to this variable will result in the value `{ a = "foo", b = null, c = 127 }`.
This functionality was introduced as an experiment in Terraform 0.14. This release removes the experimental `defaults` function. [GH-31154]
