Check for optional first before running validator (#125)

source/lib/predicates/predicate.ts

@@ -70,9 +70,13 @@ export class Predicate<T = any> implements BasePredicate<T> {
 	// tslint:disable completed-docs
 	[testSymbol](value: T, main: Main, label: string | Function) {
 		for (const {validator, message} of this.context.validators) {
+			if (this.options.optional === true && value === undefined) {
+				continue;
+			}
+
 			const result = validator(value);
 
-			if (result === true || (this.options.optional === true && value === undefined)) {
+			if (result === true) {
 				continue;
 			}
 

source/test/optional.ts

@@ -4,6 +4,7 @@ import ow from '..';
 test('optional', t => {
 	t.notThrows(() => ow(1, ow.optional.number));
 	t.notThrows(() => ow(undefined, ow.optional.number));
+	t.notThrows(() => ow(undefined, ow.optional.string.minLength(3)));
 	t.notThrows(() => ow(undefined, ow.optional.any(ow.string, ow.number)));
 	t.throws(() => ow(null, ow.optional.number), 'Expected argument to be of type `number` but received type `null`');
 	t.throws(() => ow('1' as any, ow.optional.number), 'Expected argument to be of type `number` but received type `string`');