Handle missing object property in exactShape predicate (#142)

source/utils/match-shape.ts

@@ -57,6 +57,10 @@ export function exact(object: {[key: string]: any}, shape: Shape, parent?: strin
 			if (isPredicate(shape[key])) {
 				test(object[key], label, shape[key] as BasePredicate);
 			} else if (is.plainObject(shape[key])) {
+				if (!Object.prototype.hasOwnProperty.call(object, key)) {
+					return `Expected \`${label}\` to exist`;
+				}
+
 				const result = exact(object[key], shape[key] as Shape, label);
 
 				if (result !== true) {

test/object.ts

@@ -253,6 +253,15 @@ test('object.exactShape', t => {
 			}
 		}));
 	}, 'Did not expect property `rainbow.value` to exist, got `🌈` in object `foo`');
+
+	t.throws(() => {
+		ow({unicorn: '🦄'}, ow.object.exactShape({
+			unicorn: ow.string,
+			rainbow: {
+				valid: ow.boolean
+			}
+		}));
+	}, 'Expected property `rainbow` to exist in object');
 });
 
 test('object.partialShape', t => {