fix(schema): Don't override spec values with undefined jquense#1160

src/schema.ts

@@ -1,33 +1,28 @@
 // @ts-ignore
 import cloneDeep from 'nanoclone';
-
-import { mixed as locale } from './locale';
 import Condition, { ConditionOptions, ResolveOptions } from './Condition';
-import runTests from './util/runTests';
+import { mixed as locale } from './locale';
+import { default as Ref, default as Reference } from './Reference';
+import {
+  AnyObject, Callback,
+
+
+  ExtraParams, InternalOptions,
+  Maybe, Message, TransformFunction, ValidateOptions
+} from './types';
 import createValidation, {
-  TestFunction,
   Test,
-  TestConfig,
+  TestConfig, TestFunction
 } from './util/createValidation';
 import printValue from './util/printValue';
-import Ref from './Reference';
 import { getIn } from './util/reach';
+import ReferenceSet from './util/ReferenceSet';
+import runTests from './util/runTests';
 import toArray from './util/toArray';
-import {
-  ValidateOptions,
-  TransformFunction,
-  Message,
-  Callback,
-  InternalOptions,
-  Maybe,
-  ExtraParams,
-  AnyObject,
-} from './types';
-
-import ValidationError from './ValidationError';
 import type { Asserts, Thunk } from './util/types';
-import ReferenceSet from './util/ReferenceSet';
-import Reference from './Reference';
+import ValidationError from './ValidationError';
+
+
 
 // const UNSET = 'unset' as const;
 
@@ -229,7 +224,14 @@ export default abstract class BaseSchema<
     let base = this;
     let combined = schema.clone();
 
-    const mergedSpec = { ...base.spec, ...combined.spec };
+    const baseSpec = { ...base.spec };
+    // only override with spec values which are not undefine
+    const mergedSpec = Object.keys(combined.spec).reduce((accum, key) => {
+      if (combined.spec[key] !== undefined){
+        accum[key] = combined.spec[key]
+      }
+      return accum;
+    }, baseSpec)
 
     // if (combined.spec.nullable === UNSET)
     //   mergedSpec.nullable = base.spec.nullable;