Link Multiple field with Primary

Sometimes you have hasMany relationship and need to have an ability to select primary record among related ones. As example, Contacts field of Case entity.

Need to create contacts linkMultiple field with a primary for our custom entity Stock.

Step 1

custom/Espo/Custom/Resources/metadata/entityDefs/Stock.json

{
  "fields": {
     ...
     "contacts": {
        "type": "linkMultiple",
        "view": "custom:views/stock/fields/contacts"
     },
     "contact": {
        "type": "link"
     },
     ...
  },
  "links": {
     ...
        "contact": {
            "type": "belongsTo",
            "entity": "Contact",
            "foreign": "stocksPrimary"
        },
        "contacts": {
            "type": "hasMany",
            "entity": "Contact",
            "foreign": "stocks",
            "layoutRelationshipsDisabled": true
        },
     ...
  }
}

Step 2

custom/Espo/Custom/Resources/metadata/entityDefs/Contact.json

{
  "links": {
     ...
        "stocksPrimary": {
            "type": "hasMany",
            "entity": "Stock",
            "foreign": "contact",
            "layoutRelationshipsDisabled": true
        },
        "stocks": {
            "type": "hasMany",
            "entity": "Stock",
            "foreign": "contacts"
        }
     ...
  }
}

Step 3

custom/Espo/Custom/Repositories/Stock.php

<?php

namespace Espo\Custom\Repositories;

class Stock extends \Espo\Core\ORM\Repositories\RDB
{
    public function afterSave(Entity $entity, array $options)
    {
        $result = parent::afterSave($entity, $options);
        $this->handleAfterSaveContacts($entity, $options);
        return $result;
    }
    protected function handleAfterSaveContacts(Entity $entity, array $options)
    {
        $contactIdChanged = $entity->has('contactId') && $entity->get('contactId') != $entity->getFetched('contactId');
        if ($contactIdChanged) {
            $contactId = $entity->get('contactId');
            if (empty($contactId)) {
                $this->unrelate($entity, 'contacts', $entity->getFetched('contactId'));
                return;
            }
        }
        if ($contactIdChanged) {
            $pdo = $this->getEntityManager()->getPDO();
            $sql = "
                SELECT id FROM contact_stock
                WHERE
                    contact_id = ".$pdo->quote($contactId)." AND
                    stock_id = ".$pdo->quote($entity->id)." AND
                    deleted = 0
            ";
            $sth = $pdo->prepare($sql);
            $sth->execute();
            if (!$sth->fetch()) {
                $this->relate($entity, 'contacts', $contactId);
            }
        }
    }
}

Step 4

client/custom/src/views/stock/fields/contacts.js

Espo.define('custom:views/stock/fields/contacts', 'views/fields/link-multiple-with-primary', function (Dep) {   
    return Dep.extend({
        primaryLink: 'contact'
    });
});

Step 5

Run Rebuild

Step 6

Execute SQL query

UPDATE stock
JOIN contact_stock
ON contact_stock.stock_id = stock.id AND contact_stock.deleted = 0
SET stock.contact_id = contact_stock.contact_id