fix(validation): identify invalid types for non terminal optionals

Author: mbroadst

lib/util.js

@@ -1,6 +1,7 @@
 'use strict';
 
-function validateParameter(parameter, spec) {
+function validateParameter(parameter, specs, specIndex) {
+  const spec = specs[specIndex];
   if (parameter == null && spec.required === false) {
     return;
   }
@@ -9,8 +10,13 @@ function validateParameter(parameter, spec) {
     throw new TypeError(`Required parameter \`${spec.name}\` missing`);
   }
 
-  if (spec.type && typeof parameter !== spec.type) {
-    if (spec.required === false) return false;
+  const paramType = typeof parameter;
+  if (spec.type && paramType !== spec.type) {
+    if (spec.required === false) {
+      if (specs.slice(specIndex).some(def => def.type === paramType)) {
+        return false;
+      }
+    }
 
     throw new TypeError(
       `Invalid type for parameter \`${spec.name}\`, expected \`${
@@ -48,7 +54,7 @@ function defineOperation(fn, paramDefs) {
         arg = {};
       }
 
-      if (validateParameter(arg, paramDefs[i])) {
+      if (validateParameter(arg, paramDefs, i)) {
         params.push(arg);
       } else {
         argIdx--;

test/defineOperation_tests.js

@@ -15,6 +15,12 @@ describe('defineOperation', () => {
     expect(() => testMethod(42)).to.throw(/Invalid type for parameter/);
   });
 
+  it('should validate optional parameters, with valid parameters after', function() {
+    expect(() => testMethod('llamas', false, true, () => {})).to.throw(
+      /Invalid type for parameter `optionalString`/
+    );
+  });
+
   it('should support defaults', function(done) {
     expect(() => testMethod('testing')).to.not.throw();
     testMethod('testing', true, err => {