Fix parsing of empty relative IRIs.

Author: RubenVerborgh

lib/N3Parser.js

@@ -222,7 +222,7 @@ N3Parser.prototype = {
       return this._readQuantifierList;
     default:
       // Read the subject entity
-      if (!(this._subject = this._readEntity(token)))
+      if ((this._subject = this._readEntity(token)) === undefined)
         return;
       // In N3 mode, the subject might be a path
       if (this._n3Mode)
@@ -258,7 +258,7 @@ N3Parser.prototype = {
       if (!this._n3Mode)
         return this._error('Disallowed blank node as predicate', token);
     default:
-      if (!(this._predicate = this._readEntity(token)))
+      if ((this._predicate = this._readEntity(token)) === undefined)
         return;
     }
     // The next token must be an object.
@@ -290,7 +290,7 @@ N3Parser.prototype = {
       return this._readSubject;
     default:
       // Read the object entity
-      if (!(this._object = this._readEntity(token)))
+      if ((this._object = this._readEntity(token)) === undefined)
         return;
       // In N3 mode, the object might be a path
       if (this._n3Mode)
@@ -433,7 +433,7 @@ N3Parser.prototype = {
       next = this._readDataTypeOrLang;
       break;
     default:
-      if (!(item = this._readEntity(token)))
+      if ((item = this._readEntity(token)) === undefined)
         return;
     }
 
@@ -513,7 +513,7 @@ N3Parser.prototype = {
       break;
     default:
       // An entity means this is a quad (only allowed if not already inside a graph).
-      if (this._supportsQuads && this._graph === null && (graph = this._readEntity(token))) {
+      if (this._supportsQuads && this._graph === null && (graph = this._readEntity(token)) !== undefined) {
         next = this._readQuadPunctuation;
         break;
       }
@@ -625,7 +625,7 @@ N3Parser.prototype = {
     switch (token.type) {
     case 'IRI':
     case 'prefixed':
-      if (entity = this._readEntity(token, true))
+      if ((entity = this._readEntity(token, true)) !== undefined)
         break;
     default:
       return this._error('Unexpected ' + token.type, token);
@@ -700,7 +700,7 @@ N3Parser.prototype = {
   _readForwardPath: function (token) {
     var subject, predicate, object = '_:b' + blankNodeCount++;
     // The next token is the predicate
-    if (!(predicate = this._readEntity(token)))
+    if ((predicate = this._readEntity(token)) === undefined)
       return;
     // If we were reading a subject, replace the subject by the path's object
     if (this._predicate === null)
@@ -717,7 +717,7 @@ N3Parser.prototype = {
   _readBackwardPath: function (token) {
     var subject = '_:b' + blankNodeCount++, predicate, object;
     // The next token is the predicate
-    if (!(predicate = this._readEntity(token)))
+    if ((predicate = this._readEntity(token)) === undefined)
       return;
     // If we were reading a subject, replace the subject by the path's subject
     if (this._predicate === null)

test/N3Parser-test.js

@@ -176,6 +176,15 @@ describe('N3Parser', function () {
                   ['a', 'b', 'c'],
                   ['a', 'b', 'd']));
 
+    it('should parse diamonds',
+      shouldParse('<> <> <> <>.\n(<>) <> (<>) <>.',
+                  ['', '', '', ''],
+                  ['_:b0', '', '_:b1', ''],
+                  ['_:b0', 'http://www.w3.org/1999/02/22-rdf-syntax-ns#first', ''],
+                  ['_:b0', 'http://www.w3.org/1999/02/22-rdf-syntax-ns#rest', 'http://www.w3.org/1999/02/22-rdf-syntax-ns#nil'],
+                  ['_:b1', 'http://www.w3.org/1999/02/22-rdf-syntax-ns#first', ''],
+                  ['_:b1', 'http://www.w3.org/1999/02/22-rdf-syntax-ns#rest', 'http://www.w3.org/1999/02/22-rdf-syntax-ns#nil']));
+
     it('should parse statements with named blank nodes',
       shouldParse('_:a <b> _:c.',
                   ['_:b0_a', 'b', '_:b0_c']));