Magento 2.1: <preference> doesn't work with block

Question

I try to override getSelectionTitlePrice() - function. (vendor/magento/module-bundle/Block/Catalog/Product/View/Type/Bundle/Option.php)

if i have understood right the best way to do it is use preference. Have been following lot of answers from everywhere but could not solve the problem. How to Override Core Block, Model and controller in Magento2

when i override getProduct() - function (/Block/Product/View.php) everything work but with getSelectionTitlePrice() - function it doesn't

I tried to solve problem using Plugin but it just extend function not override it?!?

app/code/MySpace/MyModule/etc/di.xml

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <preference for="Magento\Bundle\Block\Catalog\Product\View\Type\Bundle\Option" type="MySpace\MyModule\Block\Catalog\Product\View\Type\Bundle\Option" />
</config>

app/code/MySpace/MyModule/Block/Catalog/Product/View/Type/Bundle/Option.php

<?php
namespace MySpace\MyModule\Block\Catalog\Product\View\Type\Bundle;

/**
* Bundle option renderer
*/

class Option extends \Magento\Bundle\Block\Catalog\Product\View\Type\Bundle\Option
{

public function getSelectionTitlePrice($selection, $includeContainer = true)
{
    /** will be removed **/
        $logger = \Magento\Framework\App\ObjectManager::getInstance()->get('\Psr\Log\LoggerInterface');
        $logger->debug('Block Override Test');
    /** will be removed **/

    $priceTitle = '<span class="product-name">' . $this->escapeHtml($selection->getName()) . '</span>';
    $priceTitle .= ' &nbsp; ' . ($includeContainer ? '<span class="price-notice">' : '')
        . $this->renderPriceString($selection, $includeContainer) . ($includeContainer ? '</span>' : '') 
        .'<span> xxx->getTaxPercent(fromSomewhere)</span>';
    return $priceTitle;
 }
}

Answer 1

To replace a single method, use the around plugin and don't call the original method with $proceed()

Answer 2

Thanks fschmengler , I managed to solve this by using Plugin.

Override/replace single method in block class:

app/code/MySpace/MyModule/etc/di.xml

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <type name="Magento\Bundle\Block\Catalog\Product\View\Type\Bundle\Option\Radio">
        <plugin name="bundle-product-option-radio" type="MySpace\MyModule\Plugin\RadioPlugin" />
    </type>
</config>

app/code/MySpace/MyModule/Plugin/RadioPlugin.php

<?php

namespace MySpace\MyModule\Plugin;

class RadioPlugin
{

     public function aroundGetSelectionTitlePrice(
        \Magento\Bundle\Block\Catalog\Product\View\Type\Bundle\Option\Radio $subject,
        \Closure $proceed,
        $selection,
        $includeContainer = true)
    {
        $priceTitle = '<span class="product-name">' . $subject->escapeHtml($selection->getName()) . '</span>';
        $priceTitle .= ' &nbsp; ' . ($includeContainer ? '<span class="price-notice">' : '')
            . $subject->renderPriceString($selection, $includeContainer) . ($includeContainer ? '</span>' : '')
            .'<span> xxx->getTaxPercent(fromSomewhere)</span>';
        return $priceTitle;
    }
}