How to override magento-checkout CustomerData/Cart.php?

Question

I need some changes in CustomerData/Cart.php to have child products added to cart displayed in minicart. Can I make this overrides inside my Theme Folder.

I would not like to have my changes smashed on core updates.

This changes reflecting the idea behind this post: Display of "Not visible individually" for a simple product in mini cart in Magento 2

Answer 1

registration.php file,

filepath app/code/Package/Modulename/registration.php

<?php
\Magento\Framework\Component\ComponentRegistrar::register(
    \Magento\Framework\Component\ComponentRegistrar::MODULE,
    'Package_Modulename',
    __DIR__
);

composer.json file,

app/code/Package/Modulename/composer.json

{
    "name": "package/magento2-modulename",
    "description": "module desctiption",
    "require": {
        "php": "~5.5.0|~5.6.0"
    },
    "type": "magento2-module",
    "version": "1.4.0",
    "license": [
        "OSL-3.0",
        "AFL-3.0"
    ],
    "extra": {
        "map": [
            [
                "*",
                "Package/Modulename"
            ]
        ]
    }
}

module.xml file,

filepath app/code/Package/Modulename/etc/module.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd">
    <module name="Package_Modulename" setup_version="1.0.0">
    <sequence>
            <module name="Magento_Checkout"/>
        </sequence>
    </module>
</config>

di.xml file, filepath app/code/Package/Modulename/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="Magento\Checkout\CustomerData\Cart"
                 type="Package\Modulename\CustomerData\Cart" />
</config>

Cart.php file, file path, app/code/Package/Modulename/CustomerData/Cart.php

<?php


namespace Package\Modulename\CustomerData;

use Magento\Customer\CustomerData\SectionSourceInterface;

/**
 * Cart source
 */
class Cart extends \Magento\Checkout\CustomerData\Cart
{   

    /**
     * {@inheritdoc}
     */
    public function getSectionData()
    {
        $totals = $this->getQuote()->getTotals();
        return [
            'summary_count' => $this->getSummaryCount(),
            'subtotal' => isset($totals['subtotal'])
                ? $this->checkoutHelper->formatPrice($totals['subtotal']->getValue())
                : 0,
            'possible_onepage_checkout' => $this->isPossibleOnepageCheckout(),
            'items' => $this->getRecentItems(),
            'extra_actions' => $this->layout->createBlock('Magento\Catalog\Block\ShortcutButtons')->toHtml(),
            'isGuestCheckoutAllowed' => $this->isGuestCheckoutAllowed(),
        ];
    }

    /**
     * Get active quote
     *
     * @return \Magento\Quote\Model\Quote
     */
    protected function getQuote()
    {
        if (null === $this->quote) {
            $this->quote = $this->checkoutSession->getQuote();
        }
        return $this->quote;
    }

    /**
     * Get shopping cart items qty based on configuration (summary qty or items qty)
     *
     * @return int|float
     */
    protected function getSummaryCount()
    {
        if (!$this->summeryCount) {
            $this->summeryCount = $this->checkoutCart->getSummaryQty() ?: 0;
        }
        return $this->summeryCount;
    }

    /**
     * Check if one page checkout is available
     *
     * @return bool
     */
    protected function isPossibleOnepageCheckout()
    {
        return $this->checkoutHelper->canOnepageCheckout() && !$this->getQuote()->getHasError();
    }

    /**
     * Get array of last added items
     *
     * @return \Magento\Quote\Model\Quote\Item[]
     */
    protected function getRecentItems()
    {
        $items = [];
        if (!$this->getSummaryCount()) {
            return $items;
        }

        foreach (array_reverse($this->getAllQuoteItems()) as $item) {

            if (!$item->getProduct()->isVisibleInSiteVisibility()) {
                $productId = $item->getProduct()->getId();
                $products = $this->catalogUrl->getRewriteByProductStore([$productId => $item->getStoreId()]);
                if (!isset($products[$productId])) {
                    continue;
                }
                $urlDataObject = new \Magento\Framework\DataObject($products[$productId]);
                $item->getProduct()->setUrlDataObject($urlDataObject);
            }
            $items[] = $this->itemPoolInterface->getItemData($item);
        }
        return $items;
    }

    /**
     * Return customer quote items
     *
     * @return \Magento\Quote\Model\Quote\Item[]
     */
    protected function getAllQuoteItems()
    {
        if ($this->getCustomQuote()) {
            return $this->getCustomQuote()->getAllItems();
        }
        return $this->getQuote()->getAllVisibleItems();
    }

    /**
     * Check if guest checkout is allowed
     *
     * @return bool
     */
    public function isGuestCheckoutAllowed()
    {
        return $this->checkoutHelper->isAllowedGuestCheckout($this->checkoutSession->getQuote());
    }
}

you can changes funciton code inside file function.