Reflect nullable variables in Terraform 1.1.0+

[radeksimko]

Background

See hashicorp/terraform#29832 (landed in 1.1.0)

Proposal

hcl-lang

• Recognize individual expressions when nested #496
  • This may not be strictly a pre-requisite but it would likely make implementation easier if it was done before
• Ensure that null is generally recognized as semantic token type https://github.com/hashicorp/hcl-lang/blob/da78bbc8e7307ce6a4d4785821e9677769ef3efe/decoder/semantic_tokens.go#L443-L473

terraform-schema

• Add nullable as a valid attribute within variable for the relevant Terraform versions
• Ensure that we provide null as default = HERE in completion (probably via schema.LiteralValue), in addition to whatever we inferred from type
• Ensure that module input completion also provides null as option

terraform-ls

• Ensure that null is generally recognized as semantic token type

  terraform-ls/internal/lsp/token_encoder.go

  Lines 110 to 151 in 22acbc1

  	func (te *TokenEncoder) resolveTokenType(token lang.SemanticToken) (semtok.TokenType, bool) {
  	switch token.Type {
  	case lang.TokenBlockType:
  	return te.firstSupportedTokenType(
  	semtok.TokenType(lang.TokenBlockType), semtok.TokenTypeType)
  	case lang.TokenBlockLabel:
  	return te.firstSupportedTokenType(
  	semtok.TokenType(lang.TokenBlockLabel), semtok.TokenTypeEnumMember)
  	case lang.TokenAttrName:
  	return te.firstSupportedTokenType(
  	semtok.TokenType(lang.TokenAttrName), semtok.TokenTypeProperty)
  	case lang.TokenBool:
  	return te.firstSupportedTokenType(
  	semtok.TokenType(lang.TokenBool), semtok.TokenTypeKeyword)
  	case lang.TokenNumber:
  	return te.firstSupportedTokenType(
  	semtok.TokenType(lang.TokenNumber), semtok.TokenTypeNumber)
  	case lang.TokenString:
  	return te.firstSupportedTokenType(
  	semtok.TokenType(lang.TokenString), semtok.TokenTypeString)
  	case lang.TokenObjectKey:
  	return te.firstSupportedTokenType(
  	semtok.TokenType(lang.TokenObjectKey), semtok.TokenTypeParameter)
  	case lang.TokenMapKey:
  	return te.firstSupportedTokenType(
  	semtok.TokenType(lang.TokenMapKey), semtok.TokenTypeParameter)
  	case lang.TokenKeyword:
  	return te.firstSupportedTokenType(
  	semtok.TokenType(lang.TokenKeyword), semtok.TokenTypeVariable)
  	case lang.TokenTraversalStep:
  	return te.firstSupportedTokenType(
  	semtok.TokenType(lang.TokenTraversalStep), semtok.TokenTypeVariable)
  	case lang.TokenTypeCapsule:
  	return te.firstSupportedTokenType(
  	semtok.TokenType(lang.TokenTypeCapsule), semtok.TokenTypeFunction)
  	case lang.TokenTypePrimitive:
  	return te.firstSupportedTokenType(
  	semtok.TokenType(lang.TokenTypePrimitive), semtok.TokenTypeKeyword)
  	}
  	return "", false
  	}

Implementation Notes

This snippet demonstrates how HCL parser parses null: https://go.dev/play/p/GfwVLgpCsWe

[radeksimko]

This may or may not be related: hashicorp/terraform-plugin-framework#604 as I don't know how exactly are nulls represented in all the different places (e.g. whether they're still "typed" nulls).