Circular references lead to "too much recursion"

[s-tittel]

Hi and thanks for your great library!

When validating a data graph that contains circular references (e.g. hasPart / isPartOf relations) , I get:

Uncaught (in promise) InternalError: too much recursion

Here is an example to reproduce:

import N3 from 'n3'
import { Validator } from 'shacl-engine'

const dataset = new N3.Store()
const parser = new N3.Parser()
parser.parse(
`
@prefix sh:      <http://www.w3.org/ns/shacl#> .
@prefix rdfs:    <http://www.w3.org/2000/01/rdf-schema#> .
@prefix ex: <http://example.org/> .

ex:Thing
    a sh:NodeShape, rdfs:Class ;
    sh:property [ 
	          sh:path ex:hasPart ;
	          sh:node ex:ThingPart
	        ] .

ex:ThingPart
    a sh:NodeShape ;
    sh:property [ 
	          sh:path ex:isPartOf ;
	          sh:node ex:Thing ;
	        ] .        

ex:thing
    a ex:Thing ;
    ex:hasPart ex:part .

ex:part
    ex:isPartOf ex:thing .
`,
async (error, quad) => {
    if(error) throw error
    if (quad)
        dataset.addQuad(quad)
    else {
        // create a validator instance for the shapes in the given dataset
        const validator = new Validator(dataset, { factory: N3.DataFactory })

        // run the validation process
        const report = await validator.validate({ dataset })
        console.log(`conforms: ${report.conforms}`)
    }
})

Edit: I think this directly relates to rdf-ext/grapoi#13

[bergos]

@s-tittel Thanks for reporting! Sorry that it took a bit longer, but I was on vacation. I had a brief look, could reproduce the problem, and already have a solution in mind. It's similar to the grapoi problem but a bit different. Besides the visited focus node, we also need to keep the term of the shape in memory, as multiple shapes will visit the same focus node. And grapoi handles only a single sh:path walk and doesn't have the shape content. The check needs to be implemented in the shacl-engine. I will have a closer look in the next few days and implement a fix.

[s-tittel]

Hi, thanks! Just fyi, the rdf-validate-shacl library had the same issue which had been fixed by this PR. I am curious about your solution since I would like to switch to your library because of its ~200 KB smaller bundle size :-)

[bergos]

I have a working solution, but I want to double-check if it is correct and works for some edge cases. A report edge case is mentioned here. That was easy to solve as grapoi keeps track of the path and it only requires adding the path to the id of the processed shapes/focus nodes. I will get back to you once I finish my further tests.

[bergos]

I merged my changes and released a new patch version. No parameter like maxNodeChecks was required. The test was adapted a bit. Some names have been changed, making it clearer what is a shape and what is a class. Also, blank nodes have been changed to named nodes, which makes it easier to compare the expected results. And one sh:node has been replaced with a sh:or. A separate report is generated internal for logical shapes (or, and, ...). That use case should also be covered by the test.

[s-tittel]

Perfect, thanks! I am now using your library.