Features

• allow mixed schema to specify type check (3923039)
• concat() is shallow and does not merge (#1541) (a2f99d9)
• simplify base class hierarchy (#1543) (c184dcf)
• stricter when types and API (#1542) (da74254)

BREAKING CHANGES

• mixed schema are no longer treated as the base class for other schema types. It hasn't been for a while, but we've done some nasty prototype slinging to make it behave like it was. Now typescript types should be 1 to 1 with the actual classes yup exposes.

In general this should not affect anything unless you are extending (via addMethod or otherwise) mixed prototype.

import {
-  mixed,
+  Schema,
} from 'yup';

- addMethod(mixed, 'method', impl)
+ addMethod(Schema, 'method', impl)

• concat works shallowly now. Previously concat functioned like a deep merge for object, which produced confusing behavior with incompatible concat'ed schema. Now concat for objects works similar to how it works for other types, the provided schema is applied on top of the existing schema, producing a new schema that is the same as calling each builder method in order
• The function version of when() has been changed to make it easier to type. values are always passed as an array and schema, and options always the second and third argument. this is no longer set to the schema instance. and all functions must return a schema to be type safe

 string()
-   .when('other', function (other) => {
-      if (other) return this.required()
+   .when('other', ([other], schema) => {
+     return other ? schema.required() : schema
  })