GH-4921 Turtle writer does not respect namespaces in IRIs

- SimpleValueFactory.createIRI(String, String) how actually properly respects the specified namespace and localname
- TurtleWriter tries to use the namespace encoded in the IRI unless the localname contains characters which are not valid in prefixed notation
- Added test

Author: reckart

core/model/src/main/java/org/eclipse/rdf4j/model/impl/SimpleIRI.java

@@ -67,10 +67,28 @@ protected SimpleIRI(String iriString) {
 		setIRIString(iriString);
 	}
 
+	protected SimpleIRI(String namespace, String localname) {
+		setIRIString(namespace, localname);
+	}
+
 	/*---------*
 	 * Methods *
 	 *---------*/
 
+	protected void setIRIString(String namespace, String localname) {
+		Objects.requireNonNull(namespace, "namespace must not be null");
+		Objects.requireNonNull(localname, "localname must not be null");
+
+		String joinedIriString = namespace + localname;
+
+		if (joinedIriString.indexOf(':') < 0) {
+			throw new IllegalArgumentException("Not a valid (absolute) IRI: " + joinedIriString);
+		}
+
+		this.iriString = joinedIriString;
+		this.localNameIdx = namespace.length();
+	}
+
 	protected void setIRIString(String iriString) {
 		Objects.requireNonNull(iriString, "iriString must not be null");
 

core/model/src/main/java/org/eclipse/rdf4j/model/impl/SimpleValueFactory.java

@@ -85,7 +85,7 @@ public IRI createIRI(String iri) {
 
 	@Override
 	public IRI createIRI(String namespace, String localName) {
-		return createIRI(namespace + localName);
+		return new SimpleIRI(namespace, localName);
 	}
 
 	@Override

core/rio/turtle/src/main/java/org/eclipse/rdf4j/rio/turtle/TurtleUtil.java

@@ -459,6 +459,17 @@ public static String encodeURIString(String s) {
 		return s;
 	}
 
+	public static boolean isValidPrefixedName(String s) {
+		final int numberOfCodePoints = s.codePointCount(0, s.length());
+		for (int i = 1; i < numberOfCodePoints; i++) {
+			final int codePoint = s.codePointAt(i);
+			if (!isPN_CHARS(codePoint)) {
+				return false;
+			}
+		}
+		return true;
+	}
+
 	/**
 	 * Decodes an encoded Turtle string. Any \-escape sequences are substituted with their decoded value.
 	 *

core/rio/turtle/src/main/java/org/eclipse/rdf4j/rio/turtle/TurtleWriter.java

@@ -537,11 +537,20 @@ protected void writeResource(Resource res, boolean canShorten) throws IOExceptio
 	}
 
 	protected void writeURI(IRI uri) throws IOException {
-		String uriString = uri.toString();
-
-		// Try to find a prefix for the URI's namespace
 		String prefix = null;
+		if (TurtleUtil.isValidPrefixedName(uri.getLocalName())) {
+			prefix = namespaceTable.get(uri.getNamespace());
+			if (prefix != null) {
+				// Namespace is mapped to a prefix; write abbreviated URI
+				writer.write(prefix);
+				writer.write(":");
+				writer.write(uri.getLocalName());
+				return;
+			}
+		}
 
+		// Try to find a prefix for the URI's namespace
+		String uriString = uri.toString();
 		int splitIdx = TurtleUtil.findURISplitIndex(uriString);
 		if (splitIdx > 0) {
 			String namespace = uriString.substring(0, splitIdx);

core/rio/turtle/src/test/java/org/eclipse/rdf4j/rio/turtle/TurtleWriterTest.java

@@ -10,13 +10,15 @@
  *******************************************************************************/
 package org.eclipse.rdf4j.rio.turtle;
 
+import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.io.StringReader;
 import java.io.StringWriter;
 
 import org.eclipse.rdf4j.model.IRI;
 import org.eclipse.rdf4j.model.Model;
+import org.eclipse.rdf4j.model.impl.DynamicModelFactory;
 import org.eclipse.rdf4j.model.util.Models;
 import org.eclipse.rdf4j.rio.RDFFormat;
 import org.eclipse.rdf4j.rio.Rio;
@@ -672,6 +674,20 @@ public void testBlankNodeInlining_indirectCircularReferenceWithIRI() throws Exce
 		assertTrue(Models.isomorphic(expected, actual));
 	}
 
+	@Test
+	public void testIriNamespace() throws Exception {
+		Model model = new DynamicModelFactory().createEmptyModel();
+		String prefix = "foo-bar";
+		String ns = "foo:this.is.my.bar.";
+		model.setNamespace(prefix, ns);
+		model.add(vf.createIRI(ns, "lala"), vf.createIRI(ns, "lulu"), vf.createIRI(ns, "lolo"));
+
+		StringWriter stringWriter = new StringWriter();
+		Rio.write(model, stringWriter, RDFFormat.TURTLE);
+
+		assertThat(stringWriter.toString()).contains("foo-bar:lala foo-bar:lulu foo-bar:lolo .");
+	}
+
 	@Test
 	public void testIgnoreAbbreviateNumbers() throws Exception {
 		StringWriter sw = new StringWriter();