Completion/hover/highlighting for variable default

[radeksimko]

Will likely depend on #50 or at least on some parts of it.

Use-cases

Completion

Given a config

variable "test" {
  type = object({
    port = number
    protocol = string
  })
  default = {
    # HERE
  }
}

when user triggers completion in the highlighted position, they are presented with two candidates:

• port number
• protocol string

Hover

When user hovers over the expression after default = , they will be provided with a relevant popup describing type of the expression. For example

variable "test" {
  type = map(string)
  default = {
    alpha = "A"
    beta = "B"
  }
}

when hovering over { alpha ... } they would be presented with map(string).

In most cases this would basically be just whatever is in type, but if type = any, type = list(any) and similar, the hover popup should reflect the real type inferred from the value (as long as it is compatible).

Semantic Tokens

Given a config

variable "test" {
  type = string
  default = "blah"
}
variable "foo" {
  type = list(number)
  default = [ 1, 3, 5 ]
}
variable "bar" {
  type = object({
    foo = string
  })
  default = {
    foo = "test"
  }
}

• "blah" will be reported as string
• 1, 3 and 5 will be reported as number
• foo will be reported as attribute name
• "test" will be reported as string

Proposal

• (assuming Support variable files (*.tfvars) #50 is implemented as per Proposal section)
• Introduce SetVariables(map[string]module.Variable) to terraform-schema/schema.SchemaMerger
• Set relevant schema.LiteralTypeExpr to default attribute of a variable block via label-driven DependentBody. Set IsDepKey: true for the variable block label as part of SchemaMerger.SchemaForModule
• Bump terraform-schema

[github-actions]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.
If you have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.