FIX Ensure value is in the correct format after save

composer.json

@@ -26,6 +26,7 @@
         "silverstripe/recipe-testing": "^3",
         "silverstripe/standards": "^1",
         "silverstripe/documentation-lint": "^1",
+        "silverstripe/siteconfig": "^5",
         "squizlabs/php_codesniffer": "^3",
         "phpstan/extension-installer": "^1.3"
     },

src/Form/MultiLinkField.php

@@ -26,6 +26,14 @@ public function setValue(mixed $value, $data = null): static
         return parent::setValue($ids, $data);
     }
 
+    public function setSubmittedValue($value, $data = null)
+    {
+        if (is_string($value)) {
+            $value = rtrim(ltrim($value, '['), ']');
+        }
+        return $this->setValue($value, $data);
+    }
+
     public function getSchemaDataDefaults(): array
     {
         $data = parent::getSchemaDataDefaults();

tests/behat/features/linkfield-siteconfig.feature

@@ -0,0 +1,49 @@
+@retry @job2
+Feature: Create Links in LinkField and MultiLinkField on SiteConfig
+As a content editor
+I want to add links to SiteConfig which has a slightly different EditForm to SiteTree
+
+  Background:
+    Given I add an extension "SilverStripe\FrameworkTest\LinkField\Extensions\LinkPageExtension" to the "SilverStripe\SiteConfig\SiteConfig" class
+    And I go to "/dev/build?flush"
+    And I am logged in with "ADMIN" permissions
+    And I go to "/admin/settings"
+
+  Scenario: I can update and save single and multi link fields
+
+    Given I should see the "#Form_EditForm_HasOneLink" element
+    And I should see the "#Form_EditForm_HasManyLinks" element
+
+    # Saving empty fields works
+    When I press the "Save" button
+    And I wait for 2 seconds
+    Then I should see a "Saved" success toast
+
+    # Saving populated fields works
+    When I click on the "[data-field-id='Form_EditForm_HasOneLink'] button" element
+    Then I should see "Phone number" in the "[data-field-id='Form_EditForm_HasOneLink'] .dropdown-item:nth-of-type(3)" element
+    When I click on the "[data-field-id='Form_EditForm_HasOneLink'] .dropdown-item:nth-of-type(3)" element
+    And I wait for 5 seconds
+    Then I should see "Phone number" in the ".modal-header" element
+    Then I fill in "LinkText" with "Phone"
+    Then I fill in "Phone" with "12345678"
+    And I should not see "Open in new window" in the ".modal-content" element
+    And I press the "Create link" button
+    And I wait for 2 seconds
+
+    When I click on the "[data-field-id='Form_EditForm_HasManyLinks'] button" element
+    Then I should see "Phone number" in the "[data-field-id='Form_EditForm_HasManyLinks'] .dropdown-item:nth-of-type(5)" element
+    When I click on the "[data-field-id='Form_EditForm_HasManyLinks'] .dropdown-item:nth-of-type(5)" element
+    And I wait for 5 seconds
+    Then I should see "Phone number" in the ".modal-header" element
+    Then I fill in "LinkText" with "Phone"
+    Then I fill in "Phone" with "87654321"
+    And I should not see "Open in new window" in the ".modal-content" element
+    And I press the "Create link" button
+    And I wait for 2 seconds
+
+    When I press the "Save" button
+    And I wait for 2 seconds
+    Then I should see a "Saved" success toast
+    And I should see "12345678"
+    And I should see "87654321"

tests/php/Form/MultiLinkFieldTest.php

@@ -10,14 +10,14 @@
 
 class MultiLinkFieldTest extends SapphireTest
 {
-    public function provideConvertValueToArray(): array
+    private static function getDataForProvider(): array
     {
         return [
             'empty string' => [
                 'value' => '',
                 'expected' => [],
             ],
-            'non-comma-separated numeric string' => [
+            'non-comma-separated string' => [
                 'value' => 'this is a string',
                 'expected' => ['this is a string'],
             ],
@@ -29,8 +29,8 @@ public function provideConvertValueToArray(): array
                 'value' => '1,2,3,4',
                 'expected' => [1, 2, 3, 4],
             ],
-            'comma-separated string with spaces' => [
-                'value' => ' 1,2 , 3, 4  ',
+            'comma-separated string with whitesapce' => [
+                'value' => " 1,2 , 3, 4 \n ",
                 'expected' => [1, 2, 3, 4],
             ],
             'number' => [
@@ -56,6 +56,11 @@ public function provideConvertValueToArray(): array
         ];
     }
 
+    public static function provideConvertValueToArray(): array
+    {
+        return MultiLinkFieldTest::getDataForProvider();
+    }
+
     /**
      * @dataProvider provideConvertValueToArray
      */
@@ -66,4 +71,24 @@ public function testConvertValueToArray(mixed $value, array $expected): void
         $reflectionMethod->setAccessible(true);
         $this->assertSame($expected, $reflectionMethod->invoke($field, $value));
     }
+
+    public static function provideSetSubmittedValue(): array
+    {
+        return array_merge(MultiLinkFieldTest::getDataForProvider(), [
+            'comma-separated string with brackets' => [
+                'value' => '[1,2,3,4]',
+                'expected' => [1, 2, 3, 4],
+            ],
+        ]);
+    }
+
+    /**
+     * @dataProvider provideSetSubmittedValue
+     */
+    public function testSetSubmittedValue(mixed $value, array $expected): void
+    {
+        $field = new MultiLinkField('');
+        $field->setSubmittedValue($value);
+        $this->assertSame($expected, $field->Value($value));
+    }
 }