fix(manager): allow to use onChange in formSpy

Author: rvsia

packages/form-state-manager/src/files/form-spy.ts

@@ -3,7 +3,7 @@ import FormManagerContext from './form-manager-context';
 import generateId from '../utils/generate-id';
 import FormSpyProps from '../types/form-spy';
 
-const FormSpy: React.FunctionComponent<FormSpyProps> = ({ children, subscription = { all: true } }) => {
+const FormSpy: React.FunctionComponent<FormSpyProps> = ({ children, onChange, subscription = { all: true } }) => {
   const { subscribe, unsubscribe, getState, formOptions } = useContext(FormManagerContext);
   const [, rerender] = useReducer((prev) => prev + 1, 0);
 
@@ -23,7 +23,14 @@ const FormSpy: React.FunctionComponent<FormSpyProps> = ({ children, subscription
     []
   );
 
-  return children({ ...getState(), form: formOptions });
+  const newState = { ...getState(), form: formOptions };
+
+  if (onChange) {
+    onChange(newState);
+    return null;
+  }
+
+  return children(newState);
 };
 
 export default FormSpy;