Author: m@g3m@nk3y$

When you get error like: Item (MagentoCatalogModelProductInterceptor) with the same ID “<id>” already exists.

Then you can use below module to resolve above error.

1. Create new folders Magemonkey/DuplicateEntry in app/code magento folder.
2. add new file registration.php in DuplicateEntry folder and put below code.

<?php

MagentoFrameworkComponentComponentRegistrar::register(
 MagentoFrameworkComponentComponentRegistrar::MODULE,
 'Magemonkey_DuplicateEntry',
 __DIR__
);

3. add new file etc/module.xml in DuplicateEntry folder and put below code.

<?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="Magemonkey_DuplicateEntry" setup_version="1.0.1"></module>
</config>

4. add new file etc/di.xml in DuplicateEntry folder and put below code.

<?xml version="1.0"?>

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
 <type name="MagentoEavModelEntityCollectionAbstractCollection">
    <plugin name="find_duplicate_entry" type="MagemonkeyDuplicateEntrypluginCollection" sortOrder="20"/>
 </type>
</config>

5. add new file plugin/Collection.php in DuplicateEntry folder and put below code.

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 */
namespace MagemonkeyDuplicateEntryplugin;
use MagentoFrameworkDataCollectionEntityFactoryInterface;
use MagentoFrameworkOptionArrayInterface;

class Collection
{
    /**
     * @param MagentoEavModelEntityCollectionAbstractCollection $subject
     * @param Closure $process
     * @param MagentoFrameworkDataObject $dataObject
     * @return $this
     */
    public function aroundAddItem(MagentoEavModelEntityCollectionAbstractCollection $subject, Closure $process, MagentoFrameworkDataObject $dataObject)
    {
        try{
            return $process($dataObject);
        }catch ( Exception $e){
            return $this;
        }
    }
}

Add module.xml file in app/code/Magemonkeys/ShippingHide/etc and copy the following code in it:

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
	xsi:noNamespaceSchemaLocation="../../../../../lib/internal/Magento/Framework/Module/etc/module.xsd">
    <module name="Magemonkeys_ShippingHide" setup_version="2.0.10">
        <sequence>
            <module name="Magento_Shipping"/>
        </sequence>
    </module>	
</config>

Add registration.php in app/code/Magemonkeys/ShippingHide and copy the following code in it:

<?php
MagentoFrameworkComponentComponentRegistrar::register(
    MagentoFrameworkComponentComponentRegistrar::MODULE,
    'Magemonkeys_ShippingHide',
    __DIR__
);

Add Uninstall.php file in app/code/Magemonkeys/ShippingHide/Setup and copy the following code in it:

<?php

namespace MagemonkeysShippingHideSetup;

use MagentoFrameworkSetupUninstallInterface;
use MagentoFrameworkSetupModuleContextInterface;
use MagentoFrameworkSetupSchemaSetupInterface;
use MagentoConfigModelResourceModelConfigDataCollectionFactory as ConfigCollectionFactory;

/**
 * ShippingHide Uninstall
 */
class Uninstall implements UninstallInterface
{
    /**
     * Config Collection Factory
     *
     * @var MagentoConfigModelResourceModelConfigDataCollectionFactory
     */
    private $_configCollectionFactory;

    /**
     * Initialize Setup
     *
     * @param ConfigCollectionFactory $configCollectionFactory
     */
    public function __construct(
		ConfigCollectionFactory $configCollectionFactory
	) {
        $this->_configCollectionFactory = $configCollectionFactory;
    }
    
    /**
     * Uninstall DB Schema
     *
     * @param SchemaSetupInterface $setup
     * @param ModuleContextInterface $context
     * @return void
     */
    public function uninstall(SchemaSetupInterface $setup, ModuleContextInterface $context)
    {
        $setup->startSetup();
        $this->removeConfig();	
        $setup->endSetup();
    }

    /**
     * Remove Config
     *
     * @return void
     */
    private function removeConfig()
    {
        $path = 'shipping/behavior';
        /** @var MagentoConfigModelResourceModelConfigDataCollection $collection */
        $collection = $this->_configCollectionFactory->create(); 
        $collection->addPathFilter($path);

        foreach ($collection as $config) {
			$config->delete(); 	
        }
    }    
}

Add config.xml file in app/code/Magemonkeys/ShippingHide/etc and copy the following code in it:

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
	xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Store:etc/config.xsd">
    <default>
        <shipping>
            <behavior>
                <hide>1</hide>
            </behavior>
        </shipping>		
    </default>
</config>

Add di.xml file in app/code/Magemonkeys/ShippingHide/etc and copy the following code in it:

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
	xsi:noNamespaceSchemaLocation="../../../../../lib/internal/Magento/Framework/ObjectManager/etc/config.xsd">
	<!-- plugin -->		
    <type name="MagentoShippingModelRateResult">
        <plugin name="Magemonkeys_ShippingHide" type="MagemonkeysShippingHidePluginShippingModelRateResult" />
    </type>
</config>

Add system.xml file in app/code/Magemonkeys/ShippingHide/etc/adminhtml and copy the following code in it:

<?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="shipping">
	   <group id="behavior" translate="label" showInDefault="1" showInWebsite="1" showInStore="1" sortOrder="310">
                <label>Behavior of Methods</label>
                <field id="hide" translate="label comment" type="select" sortOrder="10" showInDefault="1" showInWebsite="1" showInStore="1" canRestore="1">
                    <label>Hide Mode</label>
                    <comment>Hides any other shipping methods if free shipping is available.</comment>
                    <source_model>MagentoConfigModelConfigSourceYesno</source_model>
                </field>
            </group>
        </section>
    </system>
</config>

Add Data.php file in app/code/Magemonkeys/ShippingHide/Helper and copy the following code in it:

<?php

namespace MagemonkeysShippingHideHelper;

use MagentoStoreModelScopeInterface;
use MagentoFrameworkAppHelperAbstractHelper;

/**
 * Shipping Hide Helper
 */
class Data extends AbstractHelper
{
    /**
     * Enabled Config Path
     */
    const XML_CONFIG_ENABLED = 'shipping/behavior/hide';
 	
    /**
     * Check Hide mode Functionality Should be Enabled
     *
     * @return bool
     */
    public function isEnabled()
    {
        return $this->_getConfig(self::XML_CONFIG_ENABLED);
    } 

    /**
     * Retrieve Store Configuration Data
     *
     * @param   string $path
     * @return  string|null
     */
    protected function _getConfig($path)
    {
        return $this->scopeConfig->getValue($path, ScopeInterface::SCOPE_STORE);
    }      
}

Add Result.php file in app/code/Magemonkeys/ShippingHide/Plugin/Shipping/Model/Rate and copy the following code in it:

<?php

namespace MagemonkeysShippingHidePluginShippingModelRate; 

use MagemonkeysShippingHideHelperData as ShippingHideHelper;

/**
 * Shipping Result Plugin
 */
class Result
{   
    /**
     * Helper
     *
     * @var MagemonkeysShippingHideHelperData
     */
    protected $_helper;
    
    /**
     * Initialize Plugin
     * 
     * @param ShippingHideHelper $helper
     */
    public function __construct(
        ShippingHideHelper $helper
    ) {
        $this->_helper = $helper;
    }
        	
    /**
     * Return all Rates in the Result
     *
     * @param Result $subject
     * @param Method[] $result
     * @return Method[]
     */	
    public function afterGetAllRates($subject, $result) 
    {
        if (!$this->_helper->isEnabled()) {
            return $result;
        }       		
		$rates = $this->getAllFreeRates($result);              
        return (count($rates) > 0) ? $rates : $result;
    }	
        	
    /**
     * Return all free Rates in the Result
     *
     * @param Method[] $result
     * @return Method[]
     */	
    public function getAllFreeRates($result) 
    {	
		$rates = [];
        foreach ($result ?: [] as $rate) {
            if ($rate->getPrice() < 0.0001) {
                $rates[] = $rate;
            }
        }               
        return $rates;
    }	    
}

Run CLI Commands

rm -rf var/di/* var/generation/* var/cache/* var/log/* var/page_cache/* var/session/* var/view_preprocessed/* pub/static/*
php bin/magento setup:upgrade
php bin/magento setup:upgrade
php bin/magento setup:static-content:deploy -f
php bin/magento cache:clean
php bin/magento cache:flush

Result

No method of free shipping

There is a method of free shipping

If you want to save simple product using programming use below code

1. Create file in magento 2 root named saveproduct.php

2. Put below code in saveproduct.php file

<?php

	use MagentoFrameworkAppBootstrap;
	include('app/bootstrap.php');

	// add bootstrap
	$bootstraps = Bootstrap::create(BP, $_SERVER);
	$object_Manager = $bootstraps->getObjectManager();

	$app_state = $object_Manager->get('MagentoFrameworkAppState');
	$app_state->setAreaCode('frontend');

	// get date 
	$today_date = date("m/d/Y");
	$added_date = date('m/d/Y',strtotime("+17 day"));

	$set_product = $object_Manager->create('MagentoCatalogModelProduct');

    $set_product->setWebsiteIds(array(1));
    $set_product->setAttributeSetId(9);
    $set_product->setTypeId('simple');
    $set_product->setCreatedAt(strtotime('now')); 
    // time of product creation
    $set_product->setName('Test Sample Product 2'); 
    // add Name of Product
    $set_product->setSku('add-sku-2');
    // add sku hear
    $set_product->setWeight(1.0000);
    // add weight of product
    $set_product->setStatus(1);
    $category_id = array(4,5);
    // add your catagory id
    $set_product->setCategoryIds($category_id); 
    // Product Category
    $set_product->setTaxClassId(0); 
    // type of tax class 
    // (0 - none, 1 - default, 2 - taxable, 4 - shipping)
    $set_product->setVisibility(4); 
    // catalog and search visibility
    $set_product->setManufacturer(28); 
    // manufacturer id
    $set_product->setColor(24);
    //print_r($_product);die;
    $set_product->setNewsFromDate($today_date); 
    // product set as new from
    $set_product->setNewsToDate($added_date); 
    // add image path hear
    $imagePath = "img/sony.png"; // path of the image (e.g pub/media/<image folder>)
    $set_product->addImageToMediaGallery($imagePath, array('image', 'small_image', 'thumbnail'), false, false);
    // product set as new to    
    $set_product->setCountryOfManufacture('IN'); 
    // country of manufacture (2-letter country code)
    $set_product->setPrice(100.99) ;
    // price in form 100.99
    $set_product->setCost(88.33); 
    // price in form 88.33
    $set_product->setSpecialPrice(99.85); 
    // special price in form 99.85
    $set_product->setSpecialFromDate('06/1/2016'); 
    // special price from (MM-DD-YYYY)
    $set_product->setSpecialToDate('06/30/2018'); 
    // special price to (MM-DD-YYYY)
    $set_product->setMsrpEnabled(1); 
    // enable MAP
    $set_product->setMsrpDisplayActualPriceType(1); 
    // display actual price 
    // (1 - on gesture, 2 - in cart, 3 - before order confirmation, 4 - use config)
    $set_product->setMsrp(99.99); 
    // Manufacturer's Suggested Retail Price
    $set_product->setMetaTitle('test meta title 2');
    $set_product->setMetaKeyword('test meta keyword 2');
    $set_product->setMetaDescription('test meta description 2');
    $set_product->setDescription('This is a long description');
    $set_product->setShortDescription('This is a short description');
    $set_product->setStockData(
        array(
        'use_config_manage_stock' => 0, 
        // checkbox for 'Use config settings' 
        'manage_stock' => 1, // manage stock
        'min_sale_qty' => 1, // Shopping Cart Minimum Qty Allowed 
        'max_sale_qty' => 2, // Shopping Cart Maximum Qty Allowed
        'is_in_stock' => 1, // Stock Availability of product
        'qty' => 100 // qty of product
        )
    );

    $attr1 = $set_product->getResource()->getAttribute('manufacturer');
    $avid1 = $attr1->getSource()->getOptionId('Sony'); //name in Default Store View
    $set_product->setData('manufacturer', $avid1);

    $attr2 = $set_product->getResource()->getAttribute('color');
    $avid2 = $attr2->getSource()->getOptionId('White'); //name in Default Store View
    $set_product->setData('color', $avid2);
    
    $years = array('India','Dubai','London', 'America', 'Indonesia');
    $attr3 = $set_product->getResource()->getAttribute('available_in')->getSource();
    $valuesIds = array_map(array($attr3, 'getOptionId'), $years);
    $set_product->setData('available_in', $valuesIds);


    $set_product->save();
    // get id of product
    $get_product_id = $set_product->getId();
    echo "Upload simple product id :: ".$get_product_id."n";

?>

Here I have used attributes and category as per my requirement, So you should use attributes and category as per your requirements.

If you want to Enable COD Payment Method for Particular Products, Follow below steps

You need to create an extension for this,

Here I have created extension : Magemonkeys_CodRestrict

1. Add new YES/NO product attribute i.e enable_cod_payment and set in Attribute Set which you are using for products

2. Create registration.php file in app/code/Magemonkeys/CodRestrict and add below code

<?php
MagentoFrameworkComponentComponentRegistrar::register(
MagentoFrameworkComponentComponentRegistrar::MODULE,
'Magemonkeys_CodRestrict',
__DIR__
);

3. Create module.xml file in app/code/Magemonkeys/CodRestrict/etc and add below code

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../../lib/internal/Magento/Framework/Module/etc/module.xsd">
	<module name="Magemonkeys_CodRestrict" setup_version="1.0">
	</module>
</config>

3. Create module.xml file in app/code/Magemonkeys/CodRestrict/etc and add below code

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../../lib/internal/Magento/Framework/Module/etc/module.xsd">
	<module name="Magemonkeys_CodRestrict" setup_version="1.0">
	</module>
</config>

4. Create events.xml file in app/code/Magemonkeys/CodRestrict/etc and add below code

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
    <event name="payment_method_is_active">
        <observer name="codpayment" instance="MagemonkeysCodRestrictObserverCodAvailable" />
    </event>
</config>

5. Create CodAvailable.php file in app/code/Magemonkeys/CodRestrict/Observer and add below code

<?php
 
namespace MagemonkeysCodRestrictObserver;
 
use MagentoFrameworkEventObserverInterface;
 
class CodAvailable implements ObserverInterface
{
	/**
     * payment_method_is_active event handler.
     *
     * @param MagentoFrameworkEventObserver $observer
     */
    public function execute(MagentoFrameworkEventObserver $observer)
    {
        $objectManager = MagentoFrameworkAppObjectManager::getInstance();

		$cartObj = $objectManager->get('MagentoCheckoutModelCart');

		$cartItemsCollection = $cartObj->getQuote()->getItemsCollection(); 

		$cartItemsVisible = $cartObj->getQuote()->getAllVisibleItems(); 

		$itemsArray = $cartObj->getQuote()->getAllItems();
		$enable_cod_payment = array();
		foreach($itemsArray as $item) {
			$productid = $item->getProductId();
			$product = $objectManager->create('MagentoCatalogModelProduct')->load($productid);
   			$enable_cod_payment[] = $product->getData('enable_cod_payment');   			
		}


        if($observer->getEvent()->getMethodInstance()->getCode()=="cashondelivery"){
			if(in_array(0, $enable_cod_payment)){
	            $checkResult = $observer->getEvent()->getResult();
	            $checkResult->setData('is_available', false);
	        }
    	}
    }
}

You can change payment method condition as per your need.