shawnsmith opened a new issue, #3622:
URL: https://github.com/apache/jena/issues/3622
### Version
5.6.0
### What happened?
Simple code to reproduce the NullPointerException:
```java
class DescribeTest {
@Test
void testDescribeSubstitution() {
QueryExec.graph(Graph.emptyGraph)
.query("DESCRIBE ?item")
.substitution("item",
NodeFactory.createURI("https://example.com/item";))
.build();
}
}
```
The problem is that `Query.getQueryPattern() == null` which isn't expected
by `QuerySyntaxSubstituteScope.scopeCheck()`.
There's a simple workaround:
```
# This query throws NPE
DESCRIBE ?item
# This query works
DESCRIBE ?item WHERE {}
# This approach also works
ParameterizedSparqlString sparql = new ParameterizedSparqlString("DESCRIBE
?item");
sparql.setParam("item", NodeFactory.createURI("https://example.com/item";));
Query query = sparql.asQuery();
...
```
### Relevant output and stacktrace
```shell
java.lang.NullPointerException: Cannot invoke
"org.apache.jena.sparql.syntax.Element.visit(org.apache.jena.sparql.syntax.ElementVisitor)"
because "el" is null
at
org.apache.jena.sparql.syntax.ElementWalker.walk(ElementWalker.java:37)
at
org.apache.jena.sparql.syntax.ElementWalker.walk(ElementWalker.java:32)
at
org.apache.jena.sparql.syntax.syntaxtransform.QuerySyntaxSubstituteScope.checkPattern(QuerySyntaxSubstituteScope.java:44)
at
org.apache.jena.sparql.syntax.syntaxtransform.QuerySyntaxSubstituteScope.scopeCheck(QuerySyntaxSubstituteScope.java:39)
at
org.apache.jena.sparql.syntax.syntaxtransform.QueryTransformOps.transformSubstitute(QueryTransformOps.java:113)
at
org.apache.jena.sparql.syntax.syntaxtransform.QueryTransformOps.replaceVars(QueryTransformOps.java:86)
at
org.apache.jena.sparql.exec.QueryExecDatasetBuilder.build(QueryExecDatasetBuilder.java:207)
at
org.apache.jena.arq.junit.sparql.tests.DescribeTest.testDescribeSubstitution(DescribeTest.java:16)
```
### Are you interested in making a pull request?
None
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