[fixed] array().concat() incorrectly cleared the sub-schema

src/array.js

@@ -1,5 +1,8 @@
+import typeOf from 'type-name';
+
 import inherits from './util/inherits';
 import isAbsent from './util/isAbsent';
+import isSchema from './util/isSchema';
 import MixedSchema from './mixed';
 import { mixed, array as locale } from './locale.js';
 import runValidations, { propagateErrors } from './util/runValidations';
@@ -15,7 +18,9 @@ function ArraySchema(type) {
 
   MixedSchema.call(this, { type: 'array'})
 
-  this._subType = null;
+  // `undefined` specifically means uninitialized, as opposed to
+  // "no subtype"
+  this._subType = undefined;
 
   this.withMutation(() => {
     this.transform(function(values) {
@@ -91,9 +96,27 @@ inherits(ArraySchema, MixedSchema, {
       })
   },
 
-  of(schema){
+  // concat(schema) {
+  //   var next = MixedSchema.prototype.concat.call(this, schema)
+  //
+  //   next._subType = schema._subType === undefined
+  //     ? this._subType
+  //     : schema._subType;
+  //
+  //   return next
+  // },
+
+  of(schema) {
     var next = this.clone()
-    next._subType = schema
+
+    if (schema !== false && !isSchema(schema))
+      throw new TypeError(
+        '`array.of()` sub-schema must be a valid yup schema, or `false` to negate a current sub-schema. ' +
+        'got: ' + typeOf(schema) + ' instead'
+      )
+
+    next._subType = schema;
+
     return next
   },
 

src/util/reach.js

@@ -12,18 +12,19 @@ module.exports = function (obj, path, value, context) {
   forEach(path, (_part, isBracket, isArray) => {
     let part = isBracket ? trim(_part) : _part;
 
-    if (isArray || has(obj, '_subType')) { // we skipped an array
-      let idx = isArray ? parseInt(part, 10) : 0
+    if (isArray || has(obj, '_subType')) { // we skipped an array: foo[].bar
+      let idx = isArray ? parseInt(part, 10) : 0;
+
       obj = obj.resolve({ context, parent, value })._subType;
 
       if (value) {
-
         if (isArray && idx >= value.length) {
           throw new Error(
             `Yup.reach cannot resolve an array item at index: ${_part}, in the path: ${path}. ` +
             `because there is no value at that index. `
           )
         }
+
         value = value[idx]
       }
     }
@@ -45,5 +46,9 @@ module.exports = function (obj, path, value, context) {
     }
   })
 
-  return obj && obj.resolve({ context, parent, value })
+  if (obj) {
+    obj = obj.resolve({ context, parent, value });
+  }
+
+  return obj
 }

test/array.js

@@ -63,6 +63,22 @@ describe('Array types', function(){
       .cast(['1', '3']).should.eql([1, 3])
   })
 
+  it('should concat subType correctly', function(){
+    expect(
+      array()
+        .of(number())
+        .concat(array())
+        ._subType
+    ).to.exist
+
+    expect(
+      array()
+        .of(number())
+        .concat(array().of(false))
+        ._subType
+    ).to.equal(false)
+  })
+
   it('should pass options to children', function(){
     array(
       object({ name: string() })