[Quantity] Fix .unit returns null if there is valid unit (#449)

Fixes #445.

Signed-off-by: Florian Hotze <dev@florianhotze.com>

Author: florian-h05

src/quantity.js

@@ -124,16 +124,17 @@ class Quantity {
   }
 
   /**
-   * Unit of this Quantity, e.g. `Metre`, or `null` if not available
+   * Unit name of this Quantity, e.g. `Metre`, `kWh`, or `null` if not available
    * @type {string|null}
    */
   get unit () {
-    const unit = this.rawQtyType.getUnit().getName();
+    const rawUnit = this.rawQtyType.getUnit();
+    const unit = rawUnit.getName() ?? rawUnit;
     return (unit === null) ? null : unit.toString();
   }
 
   /**
-   * Unit symbol of this Quantity, e.g. `m`, or `null` if not available
+   * Unit symbol of this Quantity, e.g. `m`, `kWh`, or `null` if not available
    * @type {string|null}
    */
   get symbol () {

test/javax-measure.mock.js

@@ -1,6 +1,7 @@
 // javax.measure.Unit (https://unitsofmeasurement.github.io/unit-api/site/apidocs/javax/measure/Unit.html)
 class Unit {
   getName = jest.fn()
+  toString = jest.fn()
 }
 
 module.exports = { Unit };

test/quantity.spec.js

@@ -39,13 +39,14 @@ describe('quantity.js', () => {
     });
 
     it('unit delegates & returns', () => {
-      unitSpy.getName.mockImplementation(() => 'Metres');
+      unitSpy.getName.mockImplementation(() => 'Metre');
       let unit = getQuantity('5 m').unit;
-      expect(unit).toBe('Metres');
+      expect(unit).toBe('Metre');
 
       unitSpy.getName.mockImplementation(() => null);
+      unitSpy.toString.mockImplementation(() => 'Metre');
       unit = getQuantity('5 m').unit;
-      expect(unit).toBe(null);
+      expect(unit).toBe('Metre');
 
       expect(unitSpy.getName).toHaveBeenCalledTimes(2);
       expect(quantityTypeSpy.getUnit).toHaveBeenCalledTimes(2);

types/quantity.d.ts

@@ -94,12 +94,12 @@ export class Quantity {
      */
     get dimension(): string;
     /**
-     * Unit of this Quantity, e.g. `Metre`, or `null` if not available
+     * Unit name of this Quantity, e.g. `Metre`, `kWh`, or `null` if not available
      * @type {string|null}
      */
     get unit(): string;
     /**
-     * Unit symbol of this Quantity, e.g. `m`, or `null` if not available
+     * Unit symbol of this Quantity, e.g. `m`, `kWh`, or `null` if not available
      * @type {string|null}
      */
     get symbol(): string;