fix: array.ensure

closes #343

src/array.js

@@ -158,17 +158,18 @@ inherits(ArraySchema, MixedSchema, {
   },
 
   ensure() {
-    return this.default(() => []).transform(val => {
-      if (this.isType(val)) return val;
-      return val === null ? [] : [].concat(val);
+    return this.default(() => []).transform((val, original) => {
+      // We don't want to return `null` for nullable schema
+      if (this._typeCheck(val)) return val;
+      return original == null ? [] : [].concat(original);
     });
   },
 
   compact(rejector) {
     let reject = !rejector ? v => !!v : (v, i, a) => !rejector(v, i, a);
 
-    return this.transform(
-      values => (values != null ? values.filter(reject) : values),
+    return this.transform(values =>
+      values != null ? values.filter(reject) : values,
     );
   },
 

test/array.js

@@ -174,6 +174,18 @@ describe('Array types', () => {
     inst.cast(a).should.equal(a);
 
     inst.cast(null).should.eql([]);
+    // nullable is redundant since this should always produce an array
+    // but we want to ensure that null is actually turned into an array
+    inst
+      .nullable()
+      .cast(null)
+      .should.eql([]);
+
+    inst.cast(1).should.eql([1]);
+    inst
+      .nullable()
+      .cast(1)
+      .should.eql([1]);
   });
 
   it('should pass resolved path to descendants', async () => {