list() does not always return an iterator

[LaurensRietveld]

The function description of list() says that it always returns an iterator. In reality, it does not:

 if (this.term) {
      if (this.term.termType !== 'NamedNode' && this.term.termType !== 'BlankNode') {
        return null
      }

      if (!this.term.equals(this.namespace.nil) && !this.out(this.namespace.first).term) {
        return null
      }
    }

This causes issues in e.g. the shacl validator where a spread operator is applied to the list() result (see here)

Depending on the structure of your data, this leads to obscure errors such as listNode.list is not a function or its return value is not iterable

[l00mi]

Thank you for pointing this out.

clownface/lib/Clownface.js

Line 138 in 479607f

* @returns {Iterable | null}

states that it can return null. Do you refer to something else?

@bergos do you remember why we went for null over an empty list?

@martinmaillard can https://github.com/zazuko/rdf-validate-shacl deal with this?

[LaurensRietveld]

Ah, I mistakenly added links to files instead of lines. I wanted to refer to this line. You're right in that the @returns tag is correct here.

Let me know if the validate-shacl library is a better place for ticket and I'll make an issue there

[tpluscode]

This is by design, IIRC to distinguish between an empty list ( ) and a non-list

[LaurensRietveld]

thanks! I'll report this in the validate-shacl repo then

[LaurensRietveld]

see zazuko/rdf-validate-shacl#73