Support splat expressions (*)

[radeksimko]

Depends on #492

This should most likely be implemented after #527

---

Background

Terraform supports splat expressions. For example:

• var.list[*].id
• var.list[*].interfaces[0].name
• var.website[*]

Language server currently doesn't support these, which means that e.g.

• we don't provide completion within a splat expression
• we don't display any details (such as type or description) on hover over splat expressions
• valid splat expressions are not highlighted via semantic tokens

Proposal

Completion

Relevant suggestions are provided via completion after . or when explicitly requested within a splat expression.

For example, given a variable

variable "list" {
  type = list(object({
    id = string
    name = string
  }))
}

user can type

var.list[*].

at which point two suggestions would come up:

• id string
• name string

Hover

Details (type, description) about a splat expression are displayed on hover.

For example, given this config

variable "list" {
  type = list(object({
    id = string
    name = string
  }))
}

output "example" {
  value = var.list[*].id
}

we display var.list[*] list of string.

Semantic Tokens

The splat operator * is recognized as such and reported as a semantic token to be highlighted accordingly.

For example in this config

output "example" {
  value = var.list[*].id
}

(the value part is already reported as attribute),var, list and id will be reported as traversal steps, and * as splat operator.