hclsyntax: Recovery of incomplete parenthesis

[radeksimko]

Context

Similar to some earlier issues, we ran into an edge case while implementing support for operators and parenthesis (ParenthesesExpr) in the Terraform language server.

attr = (

This is parsed as following:

hclsyntax.Attribute{
  Name: "attr",
  Expr: &hclsyntax.LiteralValueExpr{
    SrcRange: hcl.Range{
      Start: hcl.Pos {Line: 2, Column: 1, Byte: 9},
      End:   hcl.Pos {Line: 2, Column: 1, Byte: 9}
    }
  },
  SrcRange: hcl.Range{
    Start: hcl.Pos {Line: 1, Column: 1, Byte: 0},
    End:   hcl.Pos {Line: 2, Column: 1, Byte: 9}
  }
}

So while we can tell we are inside of an attribute and that the expression is part of the attribute - i.e. within its range, it remains awkward/difficult to figure out whether we are inside of the expression.

As with other reports related to recovery from incomplete configuration, the context is - again - enabling completion. Users would reasonably expect to be offered relevant completion in the above context, because it is exactly the nature of completion to complete the incomplete configuration.

Proposal

Report/parse the above incomplete expression with the following range:

hcl.Range{
     Start: hcl.Pos {Line: 1, Column: 8, Byte: 7},
     End:   hcl.Pos {Line: 2, Column: 1, Byte: 9}
}