Added check if gawked object has a property setter to prevent deletion.

Fixes #5.

src/index.js

@@ -56,30 +56,34 @@ export default function gawk(value, parent) {
 	} else {
 		// gawk it!
 		gawked = new Proxy(value, {
-			set: (target, prop, value) => {
+			set: (target, prop, newValue) => {
 				if (prop === '__gawk__') {
 					throw new Error('Cannot override property \'__gawk__\'');
 				}
 
-				// console.log('setting', prop, value);
+				// console.log('setting', prop, newValue);
 
 				let changed = true;
+				const desc = Object.getOwnPropertyDescriptor(target, prop);
 
-				if (Object.prototype.hasOwnProperty.call(target, prop)) {
-					changed = target[prop] !== value;
+				if (desc) {
+					changed = target[prop] !== newValue;
 					const parents = isGawked(target[prop]) && target[prop].__gawk__.parents;
 					if (parents) {
 						parents.delete(gawked);
 						if (!parents.size) {
 							target[prop].__gawk__.parents = null;
 						}
 					}
-					if (!Array.isArray(target) || prop !== 'length') {
+
+					// if the destination property has a setter, then we can't assume we need to
+					// fire a delete
+					if (typeof desc.set !== 'function' && (!Array.isArray(target) || prop !== 'length')) {
 						delete target[prop];
 					}
 				}
 
-				target[prop] = gawk(value, gawked);
+				target[prop] = gawk(newValue, gawked);
 
 				if (changed) {
 					notify(gawked);

test/test-watch.js

@@ -644,4 +644,29 @@ describe('gawk.unwatch()', () => {
 
 		expect(gobj.__gawk__.previous).to.be.null;
 	});
+
+	it('should notify when a getter/setter property is changed', () => {
+		const obj = Object.defineProperty({}, 'foo', {
+			configurable: true,
+			enumerable: true,
+			get() {
+				return this._foo;
+			},
+			set(value) {
+				this._foo = value.toUpperCase();
+			}
+		});
+
+		obj.foo = 'bar';
+
+		const gobj = gawk(obj);
+		expect(gobj.foo).to.equal('BAR');
+
+		const callback = spy();
+		gawk.watch(gobj, callback);
+
+		gobj.foo = 'baz';
+		expect(callback).to.be.calledOnce;
+		expect(gobj.foo).to.equal('BAZ');
+	});
 });