Support passing NamedNode to prefix function.

Closes #247.

Author: MPvHarmelen

src/N3Util.js

@@ -34,7 +34,7 @@ export function inDefaultGraph(quad) {
 
 // Creates a function that prepends the given IRI to a local name
 export function prefix(iri, factory) {
-  return prefixes({ '': iri }, factory)('');
+  return prefixes({ '': iri.value || iri }, factory)('');
 }
 
 // Creates a function that allows registering and expanding prefixes

test/N3Util-test.js

@@ -190,6 +190,16 @@ describe('Util', () => {
         expect(rdfs('label')).to.deep.equal(namedNode('http://www.w3.org/2000/01/rdf-schema#label'));
       });
 
+      it('should expand a NamedNode prefix', () => {
+        const rdfs = Util.prefix(namedNode('http://www.w3.org/2000/01/rdf-schema#'));
+        expect(rdfs('label')).to.deep.equal(namedNode('http://www.w3.org/2000/01/rdf-schema#label'));
+      });
+
+      it('should expand a Literal prefix', () => {
+        const rdfs = Util.prefix(literal('http://www.w3.org/2000/01/rdf-schema#'));
+        expect(rdfs('label')).to.deep.equal(namedNode('http://www.w3.org/2000/01/rdf-schema#label'));
+      });
+
       it('should use a custom factory when specified', () => {
         const factory = { namedNode: function (s) { return `n-${s}`; } };
         const rdfs = Util.prefix('http://www.w3.org/2000/01/rdf-schema#', factory);