Fix literal with empty direction not equaling undefined direction

Author: rubensworks

lib/Literal.ts

@@ -49,7 +49,8 @@ export class Literal implements RDF.Literal {
 
   public equals(other?: RDF.Term | null): boolean {
     return !!other && other.termType === 'Literal' && other.value === this.value &&
-      other.language === this.language && other.direction === this.direction &&
+      other.language === this.language &&
+      ((other.direction === this.direction) || (!other.direction && this.direction === '')) &&
       this.datatype.equals(other.datatype);
   }
 }

test/DataFactory-test.ts

@@ -138,6 +138,11 @@ describe('DataFactory', () => {
 
       expect(factory.literal('a', { language: 'en-us', direction: 'ltr' })
         .equals(factory.literal('a', { language: 'en-us', direction: 'ltr' }))).toEqual(true);
+      // Simulate old data factory before base direction existed
+      const literalNullDirection = factory.literal('a', 'en-us');
+      (<any> literalNullDirection).direction = undefined;
+      expect(factory.literal('a', { language: 'en-us', direction: '' })
+        .equals(literalNullDirection)).toEqual(true);
 
       expect(factory.literal('a')
         .equals(factory.literal('a', 'en-us'))).toEqual(false);