[Bug]: a property function is not invoked while processing QueryExecution created by QueryExecutionDatasetBuilder

[sszuev]

Version

4.6.0

What happened?

For the query

SELECT ?s WHERE {
    ?s <http://test#fun> ?o .
}

where <http://test#fun> is a custom property function, this code works as expected:

DatasetGraph dg = new DatasetGraphWrapper(DatasetGraphFactory.wrap(data.getGraph()), context);
try (QueryExecution qe = QueryExecutionFactory.create(QueryFactory.create(query), dg)) {
...
}

but this one does not work:

try (QueryExecution qe = QueryExecution.create().query(query).model(data).context(context).build()) {
...
}

from #1374

full test is attached:
TestQueryExecution.java.txt

Which environment is running?

• macOS
• Windows
• Linux
• other

Relevant output and stacktrace

No response

Are you interested in making a pull request?

No response

[sszuev]

One of the possible fix is to replace the line cxt = baseContext; with the line ctx = Context.mergeCopy(ARQ.getContext(), baseContext); in org.apache.jena.sparql.util.ContextAccumulator#buildContext: https://github.com/apache/jena/blob/main/jena-arq/src/main/java/org/apache/jena/sparql/util/ContextAccumulator.java#L145).

Not sure about side effects, but after this change there are no new fails of ARQ tests.

[afs]

I have just found that property functions have to be explicitly enabled whereas custom functions do not which is why functions work and property functions don't in the test case.

Custom functions are part of SPARQL.
Property functions are an ARQ feature.

jena/jena-arq/src/main/java/org/apache/jena/sparql/algebra/optimize/TransformPropertyFunction.java

Line 54 in ebb8b12

doingMagicProperties = context.isTrue(ARQ.enablePropertyFunctions) ;

The DatasetGraphWrapper case merges in ARQ.getContext which has this set.
new Context() does not.

Try this with and without the cxt.put:

    private static Context testContext(int id) {
        Context cxt = new Context() {
            @Override
            public String toString() {
                return "TestContext#" + id;
            }
        };
        cxt.put(ARQ.enablePropertyFunctions, true); 
        return cxt;
    }

That said, the defaults are confusing and silly.

It can be isTrueOrUndef in TransformPropertyFunction.
strictMode turns property functions off explicitly so the system default behaviour does not need to be "off".

It took me a long time to see why even my minimal case based on your test case (thank you!) wasn't working.

Sorry for all the trouble.