Comments in native SPARQL queries are not ignored by SPARQL parser

[ledsoft]

The query parser that is responsible for finding variables in SPARQL queries should ignore SPARQL comments.

The following query contains only a single parameter (x), but the parser will treat y as another variable, even though it appears in a comment.

# Selects ?y that have label "Test" - variables name is different to test ignoring variables in comments
SELECT ?x WHERE {
  ?x <http://www.w3.org/2000/01/rdf-schema#label> "Test" .
}