Magento2: How to stop a product from getting added to cart programmatically?

If youn want to stop a product from getting addded to cart programmatically, add below files to your module:

Vendor_Module\etc\di.xml

	<?xml version="1.0"?>
	<!--
	/**
	* @author Reena Parekh <reena1.parekh@gmail.com>
	*/
	-->
	<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
	<type name="Magento\Checkout\Model\Cart">
	<plugin name="interceptAddingProductToCart"
	type="Vendor\Module\Model\Checkout\Cart\AddProduct"
	sortOrder="10"
	disabled="false" />
	</type>
	</config>

view raw di.xml hosted with ❤ by GitHub

Vendor_Module\Model\Checkout\Cart\AddProduct.php

	<?php
	/**
	* @author Reena Parekh <reena1.parekh@gmail.com>
	*/
	namespace Vendor\Module\Model\Checkout\Cart;
	use Magento\Framework\Exception\LocalizedException;
	/**
	* Class AddProduct
	*/
	class AddProduct
	{
	/**
	* @var \Magento\Quote\Model\Quote
	*/
	protected $quote;
	/**
	* Plugin constructor.
	*
	* @param \Magento\Checkout\Model\Session $checkoutSession
	*/
	public function __construct(
	\Magento\Checkout\Model\Session $checkoutSession
	) {
	$this->quote = $checkoutSession->getQuote();
	}
	/**
	* beforeAddProduct
	*
	* @param $subject
	* @param $productInfo
	* @param null $requestInfo
	*
	* @return array
	* @throws LocalizedException
	*/
	public function beforeAddProduct($subject, $productInfo, $requestInfo = null)
	{
	if ($this->quote->hasData('custom_attribute')) {
	throw new LocalizedException(__('Could not add Product to Cart'));
	}
	return [$productInfo, $requestInfo];
	}
	}

view raw AddProduct.php hosted with ❤ by GitHub