GH-5573: support to refine the @context of a JSON-LD document

This change introduces a new setting for the JSONLDWriter, that allows
to configure a JSON-LD Context as Hasmac JsonDocument.

Author: aschwarte10

core/rio/jsonld/src/main/java/org/eclipse/rdf4j/rio/jsonld/JSONLDSettings.java

@@ -63,6 +63,11 @@ public class JSONLDSettings {
 	public static final RioSetting<Document> FRAME = new ClassRioSetting<>(
 			"org.eclipse.rdf4j.rio.jsonld.frame_document",
 			"A no.hasmac.jsonld.document.Document that contains the frame used for framing as specified in https://www.w3.org/TR/json-ld11-framing/",
+			null);
+
+	public static final RioSetting<Document> CONTEXT = new ClassRioSetting<>(
+			"org.eclipse.rdf4j.rio.jsonld.context_document",
+			"A no.hasmac.jsonld.document.Document that contains the JSON-LD context as specified in https://www.w3.org/TR/json-ld11/#the-context. If not defined, the context is created using the namespaces defined in the model",
 			null);;
 
 	/**

core/rio/jsonld/src/main/java/org/eclipse/rdf4j/rio/jsonld/JSONLDWriter.java

@@ -267,15 +267,24 @@ public int size() {
 				jsonld = JsonLd.flatten(JsonDocument.of(jsonld)).options(opts).get();
 				break;
 			case COMPACT:
-				JsonObjectBuilder context = Json.createObjectBuilder();
-				for (Namespace namespace : model.getNamespaces()) {
-					if (namespace.getPrefix().isEmpty()) {
-						context.add("@vocab", namespace.getName());
-					} else {
-						context.add(namespace.getPrefix(), namespace.getName());
+				Document context = writerConfig.get(JSONLDSettings.CONTEXT);
+				if (context == null) {
+
+					// define a default context using namespaces provided in the
+					// model if none is provided to the writer settings
+					JsonObjectBuilder contextBuilder = Json.createObjectBuilder();
+					for (Namespace namespace : model.getNamespaces()) {
+						if (namespace.getPrefix().isEmpty()) {
+							contextBuilder.add("@vocab", namespace.getName());
+						} else {
+							contextBuilder.add(namespace.getPrefix(), namespace.getName());
+						}
 					}
+
+					context = JsonDocument.of(contextBuilder.build());
 				}
-				jsonld = JsonLd.compact(JsonDocument.of(jsonld), JsonDocument.of(context.build())).options(opts).get();
+
+				jsonld = JsonLd.compact(JsonDocument.of(jsonld), context).options(opts).get();
 				break;
 			}
 

core/rio/jsonld/src/test/java/org/eclipse/rdf4j/rio/jsonld/JSONLDWriterTest.java

@@ -22,9 +22,15 @@
 import org.eclipse.rdf4j.model.IRI;
 import org.eclipse.rdf4j.model.Literal;
 import org.eclipse.rdf4j.model.Model;
+import org.eclipse.rdf4j.model.Namespace;
 import org.eclipse.rdf4j.model.Statement;
 import org.eclipse.rdf4j.model.impl.LinkedHashModel;
+import org.eclipse.rdf4j.model.util.ModelBuilder;
+import org.eclipse.rdf4j.model.util.Values;
 import org.eclipse.rdf4j.model.vocabulary.DCTERMS;
+import org.eclipse.rdf4j.model.vocabulary.FOAF;
+import org.eclipse.rdf4j.model.vocabulary.RDF;
+import org.eclipse.rdf4j.model.vocabulary.RDFS;
 import org.eclipse.rdf4j.model.vocabulary.XSD;
 import org.eclipse.rdf4j.rio.ParserConfig;
 import org.eclipse.rdf4j.rio.RDFFormat;
@@ -39,9 +45,12 @@
 import org.eclipse.rdf4j.rio.helpers.BasicParserSettings;
 import org.eclipse.rdf4j.rio.helpers.BasicWriterSettings;
 import org.eclipse.rdf4j.rio.helpers.StatementCollector;
+import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Disabled;
 import org.junit.jupiter.api.Test;
 
+import jakarta.json.Json;
+import jakarta.json.JsonObjectBuilder;
 import no.hasmac.jsonld.JsonLdError;
 import no.hasmac.jsonld.document.Document;
 import no.hasmac.jsonld.document.JsonDocument;
@@ -238,6 +247,69 @@ public void testFraming() throws IOException, JsonLdError {
 
 	}
 
+	@Test
+	public void testContextRefine() throws Exception {
+
+		Model model = new ModelBuilder()
+				.subject(Values.iri("https://example.com/bob"))
+				.add(RDF.TYPE, FOAF.PERSON)
+				.add(RDFS.LABEL, Values.literal("Bob", "en"))
+				.add(FOAF.NAME, Values.literal("Bob"))
+				.build();
+
+		model.setNamespace("rdfs", RDFS.NAMESPACE);
+		model.setNamespace("foaf", FOAF.NAMESPACE);
+		model.setNamespace("", "https://example.com/");
+
+		JsonDocument context = JsonDocument.of(new StringReader(""
+				+ "{\n"
+				+ "    \"rdfs\": \"http://www.w3.org/2000/01/rdf-schema#\",\n"
+				+ "    \"foaf\": \"http://xmlns.com/foaf/0.1/\",\n"
+				+ "    \"@vocab\": \"https://example.com/\",\n"
+				+ "    \"label\": {\n"
+				+ "        \"@id\": \"rdfs:label\",\n"
+				+ "        \"@container\": \"@language\"\n"
+				+ "    },\n"
+				+ "    \"name\": \"foaf:name\",\n"
+				+ "    \"Person\": \"foaf:Person\"\n"
+				+ "}"));
+
+		StringWriter sw = new StringWriter();
+
+		JSONLDWriter mpJsonLd = new JSONLDWriter(sw);
+		mpJsonLd.set(JSONLDSettings.JSONLD_MODE, JSONLDMode.COMPACT);
+		mpJsonLd.set(BasicWriterSettings.PRETTY_PRINT, true);
+		mpJsonLd.set(JSONLDSettings.CONTEXT, context);
+
+		Rio.write(model, mpJsonLd);
+
+		Assertions.assertEquals(
+				"{\n"
+						+ "    \"@id\": \"https://example.com/bob\",\n"
+						+ "    \"@type\": \"Person\",\n"
+						+ "    \"label\": {\n"
+						+ "        \"en\": \"Bob\"\n"
+						+ "    },\n"
+						+ "    \"name\": \"Bob\",\n"
+						+ "    \"@context\": {\n"
+						+ "        \"rdfs\": \"http://www.w3.org/2000/01/rdf-schema#\",\n"
+						+ "        \"foaf\": \"http://xmlns.com/foaf/0.1/\",\n"
+						+ "        \"@vocab\": \"https://example.com/\",\n"
+						+ "        \"label\": {\n"
+						+ "            \"@id\": \"rdfs:label\",\n"
+						+ "            \"@container\": \"@language\"\n"
+						+ "        },\n"
+						+ "        \"name\": \"foaf:name\",\n"
+						+ "        \"Person\": \"foaf:Person\"\n"
+						+ "    }\n"
+						+ "}",
+				sw.toString());
+
+		// test round-trip
+		Model parsed = Rio.parse(new StringReader(sw.toString()), RDFFormat.JSONLD);
+		Assertions.assertEquals(model, parsed);
+	}
+
 	@Override
 	protected RioSetting<?>[] getExpectedSupportedSettings() {
 		return new RioSetting[] {