FIX Two CMSField fixes:

- Fields that are also request handlers are now supported
- Fields that have submitted values different from saved values are now supported

src/Controllers/ElementalAreaController.php

@@ -29,12 +29,14 @@ class ElementalAreaController extends CMSMain
     private static $url_handlers = [
         // API access points with structured data
         'POST api/saveForm/$ID' => 'apiSaveForm',
+        'POST $FormName/field/$FieldName' => 'formAction',
     ];
 
     private static $allowed_actions = [
         'elementForm',
         'schema',
         'apiSaveForm',
+        'formAction',
     ];
 
     public function getClientConfig()
@@ -163,6 +165,19 @@ public function apiSaveForm(HTTPRequest $request)
         return HTTPResponse::create($body)->addHeader('Content-Type', 'application/json');
     }
 
+    public function formAction(HTTPRequest $request)
+    {
+        $formName = $request->param('FormName');
+
+        // Get the element ID from the form name
+        $id = substr($formName, strlen(sprintf(self::FORM_NAME_TEMPLATE, '')));
+        $form = $this->getElementForm($id);
+
+        $field = $form->getRequestHandler()->handleField($request);
+
+        return $field->handleRequest($request);
+    }
+
     /**
      * Remove the pseudo namespaces that were added to form fields by the form factory
      *

src/Forms/ElementalAreaField.php

@@ -241,21 +241,27 @@ public function saveInto(DataObjectInterface $dataObject)
                 continue;
             }
 
-            $fields = [];
-
             $fieldNamePrefix = sprintf(EditFormFactory::FIELD_NAMESPACE_TEMPLATE, $elementId, '');
             $prefixLength = strlen($fieldNamePrefix);
 
+            $cmsFields = $element->getCMSFields();
+
             foreach ($data as $field => $datum) {
                 // Check that the field starts with a valid name
                 if (strpos($field, $fieldNamePrefix) !== 0) {
                     continue;
                 }
 
-                $fields[substr($field, $prefixLength)] = $datum;
+                $field = $cmsFields->dataFieldByName(substr($field, $prefixLength));
+
+                if (!$field) {
+                    continue;
+                }
+
+                $field->setSubmittedValue($datum);
+                $field->saveInto($element);
             }
 
-            $element->update($fields);
             $element->write();
         }
     }