ENH Pass form validation result to client

client/src/legacy/LeftAndMain.js

@@ -489,13 +489,12 @@ $.entwine('ss', function($) {
       // Save tab selections so we can restore them later
       this.saveTabState();
 
-
       // Standard Pjax behaviour is to replace the submitted form with new content.
       // The returned view isn't always decided upon when the request
       // is fired, so the server might decide to change it based on its own logic,
       // sending back different `X-Pjax` headers and content
       jQuery.ajax(jQuery.extend({
-        headers: {"X-Pjax" : "CurrentForm,Breadcrumbs"},
+        headers: {"X-Pjax" : "CurrentForm,Breadcrumbs,ValidationResult"},
         url: form.attr('action'),
         data: formData,
         type: 'POST',

code/LeftAndMain.php

@@ -1044,6 +1044,12 @@ public function getResponseNegotiator()
                             'SilverStripe\\Admin\\CMSBreadcrumbs'
                         ]);
                     },
+                    'ValidationResult' => function () {
+                        return $this->prepareDataForPjax([
+                            'isValid' => true,
+                            'messages' => []
+                        ]);
+                    },
                     'default' => function () {
                         return $this->renderWith($this->getViewer('show'));
                     }
@@ -1492,6 +1498,12 @@ public function getEditForm($id = null, $fields = null)
                 return $negotiator->respond($request, [
                     'CurrentForm' => function () use ($result) {
                         return $result;
+                    },
+                    'ValidationResult' => function () use ($errors) {
+                        return $this->prepareDataForPjax([
+                            'isValid' => $errors->isValid(),
+                            'messages' => $errors->getMessages()
+                        ]);
                     }
                 ]);
             }
@@ -1530,6 +1542,20 @@ public function getEditForm($id = null, $fields = null)
         return $form;
     }
 
+    /**
+     * Convert an array of data to JSON and wrap it in an HTML tag as pjax is used and jQuery will parse this
+     * as an element on the client side in LeftAndMain.js handleAjaxResponse()
+     * The attribute type="application/json" denotes this is a data block and won't be processed by a browser
+     * https://html.spec.whatwg.org/#the-script-element
+     *
+     * @param array $data
+     * @return string
+     */
+    private function prepareDataForPjax(array $data): string
+    {
+        return '<script type="application/json">' . json_encode($data) . '</script>';
+    }
+
     /**
      * Returns a placeholder form, used by {@link getEditForm()} if no record is selected.
      * Our javascript logic always requires a form to be present in the CMS interface.

tests/php/LeftAndMainTest.php

@@ -14,11 +14,22 @@
 use SilverStripe\View\Requirements;
 use SilverStripe\Core\Manifest\VersionedProvider;
 use SilverStripe\Dev\Deprecation;
+use SilverStripe\Admin\Tests\LeftAndMainTest\MyTree;
+use SilverStripe\Admin\Tests\LeftAndMainTest\MyTreeController;
+use stdClass;
 
 class LeftAndMainTest extends FunctionalTest
 {
     protected static $fixture_file = 'LeftAndMainTest.yml';
 
+    protected static $extra_dataobjects = [
+        MyTree::class
+    ];
+
+    protected static $extra_controllers = [
+        MyTreeController::class
+    ];
+
     protected $backupCombined;
 
     protected function setUp(): void
@@ -238,4 +249,41 @@ public function provideTestCMSVersionNumber()
             ['myfork', 'myfork'],
         ];
     }
+
+    public function testValidationResult()
+    {
+        $this->logInAs('admin');
+
+        $obj = MyTree::create();
+        $obj->write();
+
+        $getValidationResult = function ($content) use ($obj): stdClass {
+            $response = $this->post(
+                "admin/mytree/edit/EditForm/{$obj->ID}/",
+                [
+                    'ID' => $obj->ID,
+                    'Content' => $content,
+                    'ajax' => 1,
+                    'action_save' => 1
+                ],
+                [
+                    'X-Pjax' => 'ValidationResult',
+                ]
+            );
+            $validationResultPjax = json_decode($response->getBody())->ValidationResult;
+            return json_decode(preg_replace('#</?script[^>]*?>#', '', $validationResultPjax));
+        };
+
+        // Test valid content
+        $result = $getValidationResult('Valid content');
+        $this->assertTrue($result->isValid);
+        $this->assertSame(0, count($result->messages));
+
+        // Test invalid content
+        $result = $getValidationResult(MyTree::INVALID_CONTENT);
+        $this->assertFalse($result->isValid);
+        $this->assertSame(1, count($result->messages));
+        $this->assertSame($result->messages[0]->fieldName, 'Content');
+        $this->assertSame($result->messages[0]->message, MyTree::INVALID_CONTENT_MESSAGE);
+    }
 }

tests/php/LeftAndMainTest/MyTree.php

@@ -0,0 +1,26 @@
+<?php
+
+namespace SilverStripe\Admin\Tests\LeftAndMainTest;
+
+use SilverStripe\ORM\DataObject;
+use SilverStripe\Dev\TestOnly;
+
+class MyTree extends DataObject implements TestOnly
+{
+    public const INVALID_CONTENT = 'INVALID_CONTENT';
+
+    public const INVALID_CONTENT_MESSAGE = 'INVALID_CONTENT_MESSAGE';
+
+    private static $db = [
+        'Content' => 'Varchar'
+    ];
+
+    public function validate()
+    {
+        $validationResult = parent::validate();
+        if ($this->Content === static::INVALID_CONTENT) {
+            $validationResult->addFieldError('Content', static::INVALID_CONTENT_MESSAGE);
+        }
+        return $validationResult;
+    }
+}

tests/php/LeftAndMainTest/MyTreeController.php

@@ -0,0 +1,21 @@
+<?php
+
+namespace SilverStripe\Admin\Tests\LeftAndMainTest;
+
+use SilverStripe\Admin\LeftAndMain;
+use SilverStripe\Dev\TestOnly;
+
+class MyTreeController extends LeftAndMain implements TestOnly
+{
+    private static $url_segment = 'mytree/edit';
+
+    private static $tree_class = MyTree::class;
+
+    private static $allowed_actions = [
+        'EditForm'
+    ];
+
+    private static $url_handlers = [
+        'EditForm/$ID' => 'EditForm',
+    ];
+}