Fix creation of invalid JSON when serializing functions or symbols (#299) (#300)

Author: MetalMichael

index.js

@@ -475,7 +475,7 @@ function additionalProperty (location) {
   let code = ''
   if (ap === true) {
     return `
-        if (obj[keys[i]] !== undefined) {
+        if (obj[keys[i]] !== undefined && typeof obj[keys[i]] !== 'function' && typeof obj[keys[i]] !== 'symbol') {
           ${addComma}
           json += $asString(keys[i]) + ':' + JSON.stringify(obj[keys[i]])
         }

test/additionalProperties.test.js

@@ -309,3 +309,20 @@ test('property without type but with enum, will acts as additionalProperties wit
   const obj = { ap: { additional: 'field' } }
   t.equal('{"ap":{}}', stringify(obj))
 })
+
+test('function and symbol references are not serialized as undefined', (t) => {
+  t.plan(1)
+  const stringify = build({
+    title: 'additionalProperties',
+    type: 'object',
+    additionalProperties: true,
+    properties: {
+      str: {
+        type: 'string'
+      }
+    }
+  })
+
+  const obj = { str: 'x', test: 'test', meth: () => 'x', sym: Symbol('x') }
+  t.equal('{"str":"x","test":"test"}', stringify(obj))
+})