Variable prefixes and crossref

[lou1306]

I am writing a Langium grammar for a DSL where some variables ("properties") need to be prefixed with an @ when referenced. (Something similar to Bash or Php, where $var is a reference to var).

My desiderata are:

1. The grammar should accept @var but reject @ var
2. Langium should be able to cross-ref var to its declaration.

Right now I have

{infer PropRef} '@' variable=[Prop]

This satisfies 2. but not 1 (we can put whitespace after the @ sign and the parser will not complain). If I instead write a terminal rule, such as

terminal PROPREF: /@([_a-zA-Z][\w_]*)/;

Then I can achieve 1. but not 2. because Langium looks for @var instead of var.

Is there an easy way to make it work? Ideally I would like to have a terminal rule that only returns part of the whole match (e.g., a group).

[msujew]

Hey @lou1306,

you're already doing well by using PROPREF as part of the reference. I.e. by using variable=[Prop:PROPREF].

For the second part, this becomes a bit less trivial. Langium exposes an AST element always by its canonical name. By default, this is the name that you assign using the name AST property. I.e. if you name an element var, it will only be addressable by the name var. If you want to give it a different (or even multiple) canonical names, you will need to modify the ScopeComputation service. We have a guide on how to do that here. The guide uses fully qualified name scoping, but that is also just another way of exposing an element using a different name (a fully qualified one).

[lou1306]

That worked! Thank you for pointing me in the right direction.