Merge pull request #213 from simonvbrae/feature/rdfstar_writer

Extend writer for RDF* Quads

Author: RubenVerborgh

src/N3Writer.js

@@ -1,6 +1,7 @@
 // **N3Writer** writes N3 documents.
 import namespaces from './IRIs';
 import { default as N3DataFactory, Term } from './N3DataFactory';
+import { isDefaultGraph } from './N3Util';
 
 const DEFAULTGRAPH = N3DataFactory.defaultGraph();
 
@@ -98,7 +99,7 @@ export default class N3Writer {
       // Different subject; write the whole quad
       else
         this._write((this._subject === null ? '' : '.\n') +
-                    this._encodeIriOrBlank(this._subject = subject) + ' ' +
+                    this._encodeSubject(this._subject = subject) + ' ' +
                     this._encodePredicate(this._predicate = predicate) + ' ' +
                     this._encodeObject(object), done);
     }
@@ -114,7 +115,7 @@ export default class N3Writer {
 
   // ### `quadToString` serializes a quad as a string
   quadToString(subject, predicate, object, graph) {
-    return  this._encodeIriOrBlank(subject)   + ' ' +
+    return  this._encodeSubject(subject)   + ' ' +
             this._encodeIriOrBlank(predicate) + ' ' +
             this._encodeObject(object) +
             (graph && graph.value ? ' ' + this._encodeIriOrBlank(graph) + ' .\n' : ' .\n');
@@ -127,6 +128,12 @@ export default class N3Writer {
     }, this).join('');
   }
 
+  // ### `_encodeSubject` represents a subject
+  _encodeSubject(entity) {
+    return entity.termType === 'Quad' ?
+      this._encodeQuad(entity) : this._encodeIriOrBlank(entity);
+  }
+
   // ### `_encodeIriOrBlank` represents an IRI or blank node
   _encodeIriOrBlank(entity) {
     // A blank node or list is represented as-is
@@ -168,7 +175,23 @@ export default class N3Writer {
 
   // ### `_encodeObject` represents an object
   _encodeObject(object) {
-    return object.termType === 'Literal' ? this._encodeLiteral(object) : this._encodeIriOrBlank(object);
+    switch (object.termType) {
+    case 'Quad':
+      return this._encodeQuad(object);
+    case 'Literal':
+      return this._encodeLiteral(object);
+    default:
+      return this._encodeIriOrBlank(object);
+    }
+  }
+
+  // ### `_encodeQuad` encodes an RDF* quad
+  _encodeQuad({ subject, predicate, object, graph }) {
+    return `<<${
+      this._encodeSubject(subject)} ${
+      this._encodePredicate(predicate)} ${
+      this._encodeObject(object)}${
+      isDefaultGraph(graph) ? '' : ` ${this._encodeIriOrBlank(graph)}`}>>`;
   }
 
   // ### `_blockedWrite` replaces `_write` after the writer has been closed

test/N3Writer-test.js

@@ -494,7 +494,7 @@ describe('Writer', function () {
       writer.addQuad(new NamedNode('a3'), new NamedNode('b'), new BlankNode('m3'));
       writer.end(function (error, output) {
         output.should.equal('(<c> <d> <e>) <b> ("c" "d" "e").\n' +
-                            '<a3> <b> _:m3.\n');
+          '<a3> <b> _:m3.\n');
         done(error);
       });
     });
@@ -569,6 +569,66 @@ describe('Writer', function () {
         done();
       });
     });
+
+    it('should serialize a triple with a triple with mixed component types as subject', function () {
+      var writer = new Writer();
+      writer.quadToString(new Quad(new BlankNode('b1'), new NamedNode('b'), new Literal('l1')), new NamedNode('b'), new NamedNode('c')).should.equal('<<_:b1 <b> "l">> <b> <c> .\n');
+    });
+
+    it('should serialize a triple with a triple with iris as subject', function () {
+      var writer = new Writer();
+      writer.quadToString(new Quad(new NamedNode('a'), new NamedNode('b'), new NamedNode('c')), new NamedNode('b'), new NamedNode('c')).should.equal('<<<a> <b> <c>>> <b> <c> .\n');
+    });
+
+    it('should serialize a triple with a triple with blanknodes as subject', function () {
+      var writer = new Writer();
+      writer.quadToString(new Quad(new BlankNode('b1'), new BlankNode('b2'), new BlankNode('b3')), new NamedNode('b'), new NamedNode('c')).should.equal('<<_:b1 _:b2 _:b3>> <b> <c> .\n');
+    });
+
+    it('should serialize a triple with a triple as object', function () {
+      var writer = new Writer();
+      writer.quadToString(new NamedNode('a'), new NamedNode('b'), new Quad(new BlankNode('b1'), new NamedNode('b'), new Literal('l1'))).should.equal('<a> <b> <<_:b1 <b> "l">> .\n');
+    });
+
+    it('should serialize a triple with a triple with iris as object', function () {
+      var writer = new Writer();
+      writer.quadToString(new NamedNode('a'), new NamedNode('b'), new Quad(new NamedNode('a'), new NamedNode('b'), new NamedNode('c'))).should.equal('<a> <b> <<<a> <b> <c>>> .\n');
+    });
+
+    it('should serialize a triple with a triple with blanknodes as object', function () {
+      var writer = new Writer();
+      writer.quadToString(new NamedNode('a'), new NamedNode('b'), new Quad(new BlankNode('b1'), new BlankNode('b2'), new BlankNode('b3'))).should.equal('<a> <b> <<_:b1 _:b2 _:b3>> .\n');
+    });
+
+    it('should serialize a quad with a triple with mixed component types as subject', function () {
+      var writer = new Writer();
+      writer.quadToString(new Quad(new NamedNode('a'), new NamedNode('b'), new NamedNode('c')), new NamedNode('b'), new NamedNode('c'), new NamedNode('g')).should.equal('<<<a> <b> <c>>> <b> <c> <g> .\n');
+    });
+
+    it('should serialize a quad with a triple as object', function () {
+      var writer = new Writer();
+      writer.quadToString(new NamedNode('a'), new NamedNode('b'), new Quad(new NamedNode('a'), new NamedNode('b'), new NamedNode('c')), new NamedNode('g')).should.equal('<a> <b> <<<a> <b> <c>>> <g> .\n');
+    });
+
+    it('should serialize a quad with a quad as subject', function () {
+      var writer = new Writer();
+      writer.quadToString(new Quad(new NamedNode('a'), new NamedNode('b'), new NamedNode('c'), new NamedNode('g')), new NamedNode('b'), new NamedNode('c'), new NamedNode('g')).should.equal('<<<a> <b> <c> <g>>> <b> <c> <g> .\n');
+    });
+
+    it('should serialize a quad with a quad as object', function () {
+      var writer = new Writer();
+      writer.quadToString(new NamedNode('a'), new NamedNode('b'), new Quad(new NamedNode('a'), new NamedNode('b'), new NamedNode('c'), new NamedNode('g')), new NamedNode('g')).should.equal('<a> <b> <<<a> <b> <c> <g>>> <g> .\n');
+    });
+
+    it('should serialize a triple with a quad as subject', function () {
+      var writer = new Writer();
+      writer.quadToString(new Quad(new NamedNode('a'), new NamedNode('b'), new NamedNode('c'), new NamedNode('g')), new NamedNode('b'), new NamedNode('c')).should.equal('<<<a> <b> <c> <g>>> <b> <c> .\n');
+    });
+
+    it('should serialize a triple with a quad as object', function () {
+      var writer = new Writer();
+      writer.quadToString(new NamedNode('a'), new NamedNode('b'), new Quad(new NamedNode('a'), new NamedNode('b'), new NamedNode('c'), new NamedNode('g'))).should.equal('<a> <b> <<<a> <b> <c> <g>>> .\n');
+    });
   });
 });