Correct string literal constructor.

Fixes #189.

Author: RubenVerborgh

src/N3DataFactory.js

@@ -290,30 +290,28 @@ function literal(value, languageOrDataType) {
   if (typeof languageOrDataType === 'string')
     return new Literal('"' + value + '"@' + languageOrDataType.toLowerCase());
 
-  // Create a datatyped literal
-  var datatype = languageOrDataType && languageOrDataType.value || '';
-  if (!datatype) {
-    switch (typeof value) {
+  // Automatically determine datatype for booleans and numbers
+  let datatype = languageOrDataType ? languageOrDataType.value : '';
+  if (datatype === '') {
     // Convert a boolean
-    case 'boolean':
+    if (typeof value === 'boolean')
       datatype = xsd.boolean;
-      break;
     // Convert an integer or double
-    case 'number':
+    else if (typeof value === 'number') {
       if (Number.isFinite(value))
         datatype = Number.isInteger(value) ? xsd.integer : xsd.double;
       else {
         datatype = xsd.double;
         if (!Number.isNaN(value))
           value = value > 0 ? 'INF' : '-INF';
       }
-      break;
-    // No datatype, so convert a plain string
-    default:
-      return new Literal('"' + value + '"');
     }
   }
-  return new Literal('"' + value + '"^^' + datatype);
+
+  // Create a datatyped literal
+  return (datatype === '' || datatype === xsd.string) ?
+    new Literal('"' + value + '"') :
+    new Literal('"' + value + '"^^' + datatype);
 }
 
 // ### Creates a variable

test/N3DataFactory-test.js

@@ -49,6 +49,10 @@ describe('DataFactory', function () {
       DataFactory.literal('abc', new NamedNode('http://ex.org/type')).should.deep.equal(new Literal('"abc"^^http://ex.org/type'));
     });
 
+    it('converts a non-empty string with an xsd:string type', function () {
+      DataFactory.literal('abc', new NamedNode('http://www.w3.org/2001/XMLSchema#string')).should.deep.equal(new Literal('"abc"'));
+    });
+
     it('converts an integer', function () {
       DataFactory.literal(123).should.deep.equal(new Literal('"123"^^http://www.w3.org/2001/XMLSchema#integer'));
     });