Magento2: In the admin under Stores Configuration, how can I make changes to an existing field made in the vendor?

Question

So in the Magento2 admin, under Stores > Configuration > Sales > Checkout > Shopping Cart, I would like the "After Adding a Product Redirect to Shopping Cart" dropdown with the Yes/No option to either: -Only have the option to set it to "No". -Have a comment for the field, so that the customer only knows to set it to "No".

I see the field is created in the Magento2 vendor in this file: "vendor/magento/module-checkout/etc/adminhtml/system.xml" (in the code below, see the field tag with the id "redirect_to_cart", in the group tag with the id "cart".

<?xml version="1.0"?>
<!--
/**
 * Copyright © 2016 Magento. All rights reserved.
 * See COPYING.txt for license details.
 */
-->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Config:etc/system_file.xsd">
    <system>
        <section id="checkout" translate="label" type="text" sortOrder="305" showInDefault="1" showInWebsite="1" showInStore="1">
            <label>Checkout</label>
            <tab>sales</tab>
            <resource>Magento_Checkout::checkout</resource>
            <group id="options" translate="label" type="text" sortOrder="1" showInDefault="1" showInWebsite="1" showInStore="1">
                <label>Checkout Options</label>
                <field id="onepage_checkout_enabled" translate="label" type="select" sortOrder="5" showInDefault="1" showInWebsite="1" showInStore="1">
                    <label>Enable Onepage Checkout</label>
                    <source_model>Magento\Config\Model\Config\Source\Yesno</source_model>
                </field>
                <field id="guest_checkout" translate="label" type="select" sortOrder="10" showInDefault="1" showInWebsite="1" showInStore="1">
                    <label>Allow Guest Checkout</label>
                    <source_model>Magento\Config\Model\Config\Source\Yesno</source_model>
                </field>
                <field id="customer_must_be_logged" translate="label" type="select" sortOrder="15" showInDefault="1" showInWebsite="1" showInStore="0">
                    <label>Require Customer To Be Logged In To Checkout</label>
                    <source_model>Magento\Config\Model\Config\Source\Yesno</source_model>
                    <depends>
                        <field id="guest_checkout">0</field>
                    </depends>
                </field>
            </group>
            <group id="cart" translate="label" sortOrder="2" showInDefault="1" showInWebsite="1" showInStore="1">
                <label>Shopping Cart</label>
                <field id="delete_quote_after" translate="label" type="text" sortOrder="1" showInDefault="1" showInWebsite="1" showInStore="0">
                    <label>Quote Lifetime (days)</label>
                </field>
                <field id="redirect_to_cart" translate="label" type="select" sortOrder="2" showInDefault="1" showInWebsite="1" showInStore="1">
                    <label>After Adding a Product Redirect to Shopping Cart</label>
                    <source_model>Magento\Config\Model\Config\Source\Yesno</source_model>
                </field>
            </group>
            <group id="cart_link" translate="label" sortOrder="3" showInDefault="1" showInWebsite="1" showInStore="0">
                <label>My Cart Link</label>
                <field id="use_qty" translate="label" type="select" sortOrder="1" showInDefault="1" showInWebsite="1" showInStore="0">
                    <label>Display Cart Summary</label>
                    <source_model>Magento\Checkout\Model\Config\Source\Cart\Summary</source_model>
                </field>
            </group>
            <group id="sidebar" translate="label" sortOrder="4" showInDefault="1" showInWebsite="1" showInStore="1">
                <label>Shopping Cart Sidebar</label>
                <field id="display" translate="label" type="select" sortOrder="1" showInDefault="1" showInWebsite="1" showInStore="1">
                    <label>Display Shopping Cart Sidebar</label>
                    <source_model>Magento\Config\Model\Config\Source\Yesno</source_model>
                </field>
                <field id="count" translate="label" type="text" sortOrder="2" showInDefault="1" showInWebsite="1" showInStore="1">
                    <label>Maximum Display Recently Added Item(s)</label>
                </field>
            </group>
            <group id="payment_failed" translate="label" type="text" sortOrder="100" showInDefault="1" showInWebsite="1" showInStore="1">
                <label>Payment Failed Emails</label>
                <field id="identity" translate="label" type="select" sortOrder="1" showInDefault="1" showInWebsite="1" showInStore="1">
                    <label>Payment Failed Email Sender</label>
                    <source_model>Magento\Config\Model\Config\Source\Email\Identity</source_model>
                </field>
                <field id="receiver" translate="label" type="select" sortOrder="1" showInDefault="1" showInWebsite="1" showInStore="1">
                    <label>Payment Failed Email Receiver</label>
                    <source_model>Magento\Config\Model\Config\Source\Email\Identity</source_model>
                </field>
                <field id="template" translate="label comment" type="select" sortOrder="2" showInDefault="1" showInWebsite="1" showInStore="1">
                    <label>Payment Failed Template</label>
                    <comment>Email template chosen based on theme fallback when "Default" option is selected.</comment>
                    <source_model>Magento\Config\Model\Config\Source\Email\Template</source_model>
                </field>
                <field id="copy_to" translate="label comment" type="text" sortOrder="4" showInDefault="1" showInWebsite="1" showInStore="1">
                    <label>Send Payment Failed Email Copy To</label>
                    <comment>Separate by ",".</comment>
                </field>
                <field id="copy_method" translate="label" type="select" sortOrder="5" showInDefault="1" showInWebsite="1" showInStore="1">
                    <label>Send Payment Failed Email Copy Method</label>
                    <source_model>Magento\Config\Model\Config\Source\Email\Method</source_model>
                </field>
            </group>
        </section>
    </system>
</config>

Answer 1

I found out how to add a comment to an existing field in Stores Configuration in the Admin! I just created a system.xml file in a new extension, and used the existing section id, group id, and field id. Here is my code in /etc/adminhtml/system.xml :

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Config:etc/system_file.xsd">
    <system>
        <section id="checkout" translate="label" type="text" sortOrder="305" showInDefault="1" showInWebsite="1" showInStore="1">
            <group id="cart" translate="label" sortOrder="2" showInDefault="1" showInWebsite="1" showInStore="1">
                <field id="redirect_to_cart" translate="label" type="select" sortOrder="2" showInDefault="1" showInWebsite="1" showInStore="1">
                    <comment>Please only set value to "No".</comment>
                </field>
            </group>
        </section>
    </system>
</config>

Answer 2

How about setting a different source_model to a custom model like below?

<?php
namespace MyModule\MyExample\Model\Config\Source;

class No implements \Magento\Framework\Option\ArrayInterface
{
    /**
     * Options getter
     *
     * @return array
     */
    public function toOptionArray()
    {
        return [['value' => 0, 'label' => __('No')]];
    }

    /**
     * Get options in "key-value" format
     *
     * @return array
     */
    public function toArray()
    {
        return [0 => __('No')];
    }
}

Answer 3

Steps to Override Vendor Configuration Field:

=> Create a Custom Module:

In your Magento 2 installation, create a new module. You can place it in the app/code directory or use a composer-based approach.

=> Declare Dependency Injection Preference:

In your custom module, declare a preference in the di.xml file to override the vendor class responsible for the configuration.

app/code/YourVendor/YourModule/etc/di.xml

<?xml version="1.0" ?><config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd"><preference for="Vendor\Module\Model\Config" type="YourVendor\YourModule\Model\Config" /></config>

=> Create a Custom Configuration Model:

Now, create a custom configuration model that extends the vendor's configuration model. Override the method where the configuration field is defined.

=> app/code/YourVendor/YourModule/Model/Config.php

<?php namespace YourVendor\YourModule\Model; use Vendor\Module\Model\Config as VendorConfig; class Config extends VendorConfig { public function getYourCustomField() { // Your custom logic to get the value of the field // You can modify or replace the logic from the vendor class } }

=> Update Configuration:

Update your configuration field in your custom model according to your requirements.

=> Clear Cache:

After making changes, clear the Magento cache to apply the configuration overrides.

php bin/magento cache:clean