MultiLinkField on SiteConfig returns "Failed to load link(s)" on Save

[TheSceneman]

Module version(s) affected

4.2.3

Description

When a MultiLinkField is added to SiteConfig via extension and updateCMSFields() it says "Failed to load link(s)" after the SiteConfig is saved. The links are saved, it is the retrieval of the updated list of links which is failing. See screenshot below from Network tab of Chrome dev tools. Subsequent requests add more square brackets:

How to reproduce

Add extension to siteconfig

SilverStripe\SiteConfig\SiteConfig:
  extensions:
    - App\Extensions\SiteConfigExtension

<?php

namespace App\Extensions;

use SilverStripe\Core\Extension;
use SilverStripe\Forms\FieldList;
use SilverStripe\LinkField\Form\MultiLinkField;
use SilverStripe\LinkField\Models\Link;

class SiteConfigExtension extends Extension
{

    private static array $has_many = [
        'ConfigLinks' => Link::class . '.Owner',
    ];

    private static array $owns = [
        'ConfigLinks',
    ];

    public function updateCMSFields(FieldList $fields)
    {
        $fields->addFieldToTab('Root.Main', MultiLinkField::create('ConfigLinks'));
    }
    
}

Then navigate to siteconfig via {yourdomain}/admin/settings. Add a new link of any type via the Configlinks field.
Click save, you should see the error message. If you refresh the page you will see the links have been saved OK.

Possible Solution

I rolled the silverstripe/linkfield version back to 4.0.0 and this fixed the issue, so the breaking change has been introduced between 4.0.0 and 4.2.3

Validations

• Check that there isn't already an issue that reports the same bug
• Double check that your reproduction steps work in a fresh installation of silverstripe/installer (with any code examples you've provided)

PRs

• FIX Ensure value is in the correct format after save #386

[GuySartorelli]

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[TheSceneman]

If the internal slack conversation is relevant, please include it here in plain text. Not everyone who can see this issue has access to our internal slack.

Theres nothing in there that adds anything tbh, I'll remove the link