ENH Allow a parent field to manage its child field state.

Author: GuySartorelli

src/Forms/Schema/FormSchema.php

@@ -207,7 +207,18 @@ protected function getFieldStates($fields)
     {
         $states = [];
         foreach ($fields as $field) {
-            $states[] = $field->getSchemaState();
+            $fieldState = $field->getSchemaState();
+
+            // getSchema() allows fields to contain nested schema for their children.
+            // The PHPDoc for getState says it should too - but it doesn't, and there are
+            // backwards compatibility concerns with allowing that with the "children" array key.
+            // Allow a special "child-state-to-fold-in" for nested data instead.
+            if (isset($fieldState['child-state-to-fold-in'])) {
+                $states = array_merge($states, $fieldState['child-state-to-fold-in']);
+                unset($fieldState['child-state-to-fold-in']);
+            }
+
+            $states[] = $fieldState;
 
             if ($field instanceof CompositeField) {
                 $subFields = $field->FieldList();