Support setting parent error from child

Author: CodeStix

example/src/App.tsx

@@ -288,7 +288,7 @@ export function Form() {
                     <hr />
                     <h3>Togglable object field</h3>
                     <label>
-                        <FormInput form={form} name="author" type="checkbox" setNullOnUncheck value={{ name: "", age: 0 }} />
+                        <FormInput form={form} name="author" type="checkbox" setUndefinedOnUncheck value={{ name: "", age: 0 }} />
                         Enable author
                     </label>
                     <ChildForm
@@ -301,6 +301,10 @@ export function Form() {
                                     <FormInput form={form} name="name" />
                                     <p>Age</p>
                                     <FormInput form={form} name="age" type="number" />
+                                    <button type="button" onClick={() => form.setErrors("This is a parent error")}>
+                                        Set parent error
+                                    </button>
+                                    j
                                 </div>
                             </VisualRender>
                         )}

example/src/index.tsx

@@ -7,6 +7,7 @@ import OneOfObjectArrayForm from "./OneOfObjectArrayForm";
 import { BrowserRouter, Route, Switch } from "react-router-dom";
 import { StyledForm } from "./StyledForm";
 import { ExampleForm } from "./ExampleForm";
+import App from "./App";
 
 function Router() {
     return (
@@ -15,6 +16,7 @@ function Router() {
                 <Route path="/object-types" component={OneOfObjectForm} />
                 <Route path="/object-types-array" component={OneOfObjectArrayForm} />
                 <Route path="/styled-form" component={StyledForm} />
+                <Route path="/test" component={App} />
                 <Route path="/" component={ExampleForm} />
             </Switch>
         </BrowserRouter>

src/form.ts

@@ -1,6 +1,6 @@
 export type ListenerCallback = () => void;
 export type ListenerMap = { [T in string]?: ListenerCallback };
-export type Validator<T, Error> = (values: T) => ErrorMap<T, Error> | Promise<ErrorMap<T, Error>>;
+export type Validator<T, Error> = (values: T) => ErrorType<T, Error> | Promise<ErrorType<T, Error>>;
 
 export type ChildFormMap<T, State, Error extends string> = {
     [Key in keyof T]?: ChildFormState<T, Key, State, Error>;
@@ -10,7 +10,7 @@ export type DirtyMap<T> = {
     [Key in keyof T]?: boolean;
 };
 
-export type ErrorType<T, Error> = T extends object ? ErrorMap<T, Error> | Error : Error;
+export type ErrorType<T, Error> = Error | (T extends {} ? ErrorMap<T, Error> : never);
 
 export type ErrorMap<T, Error> = {
     [Key in keyof T]?: ErrorType<T[Key], Error>;
@@ -329,7 +329,7 @@ export class FormState<T, State = DefaultState, Error extends string = DefaultEr
                 let changed = this.childMap[key]!.setErrors((error as any) ?? {}, true, false);
                 if (!changed) return false;
             } else {
-                this.childMap[key]!.setErrors({}, true, false);
+                this.childMap[key]!.setErrors({} as any, true, false);
             }
         }
 
@@ -345,7 +345,13 @@ export class FormState<T, State = DefaultState, Error extends string = DefaultEr
      * @param notifyChild Should this form notify the child form about this change?
      * @param notifyParent Should this form notify the parent form about this change?
      */
-    public setErrors(errors: ErrorMap<T, Error>, notifyChild: boolean = true, notifyParent: boolean = true) {
+    public setErrors(errors: ErrorType<T, Error>, notifyChild: boolean = true, notifyParent: boolean = true) {
+        if (typeof errors === "string") {
+            if (notifyParent && this instanceof ChildFormState) {
+                this.parent.setError(this.name, errors, false, true);
+            }
+            return;
+        }
         let keys = Object.keys(this.errorMap);
         let newKeys = Object.keys(errors);
         for (let i = 0; i < newKeys.length; i++) {