Best way to set up helper declarations using same tag in different modules

Question

My application (CE Magento 1.9) has two extensions, a custom theme and checkout module, that is using the same xml tag which I believe is causing the following error when visiting the site:

Fatal error: Call to undefined method Webtex_OnePageCheckout_Helper_Data::isOnepageCheckoutEnabled() in C:\Sites\mycompany\app\code\community\Trego\OnepageCheckout\Block\Links.php on line 6

Line 6 is as follows:

if ($this->helper('onepagecheckout')->isOnepageCheckoutEnabled())

Helper snippet from local/Webtex/OnePageCheckout/etc/config.xml:

<helpers>
    <onepagecheckout>
        <class>Webtex_OnePageCheckout_Helper</class>
    </onepagecheckout>
</helpers>

Helper snippet from community/Trego/OnepageCheckout/etc/config.xml:

<helpers>
    <checkout>
        <rewrite>
            <url>Trego_OnepageCheckout_Helper_Url</url>
        </rewrite>
    </checkout>
    <onepagecheckout>
        <class>Trego_OnepageCheckout_Helper</class>
    </onepagecheckout>
</helpers>

What is the best way to get my application working while keeping both vendor plugins installed? As you can see from the error, the application is referencing the "wrong" class for the isOnepageCheckoutEnabled() method. From my research, it sounds like I could rename one of the tags or use the tag in config.xml but being new to Magento, I'm hoping somebody can point me in the right direction.

It's almost as if I need to combine the helper classes from each extension, but I don't think I can use the PHP's extend function. Here are the relevant helper files:

community/Trego/OnepageCheckout/Block/Links.php:

<?php
class Trego_OnepageCheckout_Block_Links extends Mage_Checkout_Block_Links
{
    public function addCheckoutLink()
    {
        if ($this->helper('onepagecheckout')->isOnepageCheckoutEnabled()) 
        {
            $parent = $this->getParentBlock();
            if ($parent)
                $parent->addLink($this->helper('onepagecheckout')->__('Checkout'), 'onepagecheckout', $this->helper('onepagecheckout')->__('Checkout'), true, array('_secure'=> true), 60, null, 'class="top-link-checkout"');

            return $this;
        }
        else
            return parent::addCheckoutLink();
    }
}

local/Webtex/OnePageCheckout/Helper/Data.php:

<?php

class Webtex_OnePageCheckout_Helper_Data extends Mage_Core_Helper_Data
{

    const XML_PATH_GUEST_CHECKOUT                  = 'checkout/options/guest_checkout';
    const XML_ONEPAGECHECKOUT_ENABLED              = 'onepagecheckout/default/enabled';
    const XML_ONEPAGECHECKOUT_GUESTALLOW           = 'onepagecheckout/default/guestallow';
    const XML_ONEPAGECHECKOUT_DEFAULTDESIGN        = 'onepagecheckout/default/default_design';
    const XML_ONEPAGECHECKOUT_CARTENABLED          = 'onepagecheckout/default/cartenabled';
    const XML_ONEPAGECHECKOUT_SUMMARY              = 'onepagecheckout/default/summary';
    const XML_ONEPAGECHECKOUT_STEP1_TITLE          = 'onepagecheckout/step_1/steptitle';
    const XML_ONEPAGECHECKOUT_NOLOGIN              = 'onepagecheckout/step_1/nologin';
    const XML_ONEPAGECHECKOUT_LOGINCHECKOUT        = 'onepagecheckout/step_1/logincheckout';
    const XML_ONEPAGECHECKOUT_STEP2_TITLE          = 'onepagecheckout/step_2/steptitle';
    const XML_ONEPAGECHECKOUT_STEP2_ADDRESSBOOK    = 'onepagecheckout/step_2/addressbook';
    const XML_ONEPAGECHECKOUT_STEP2_FIRSTNAME      = 'onepagecheckout/step_2/firstname';
    const XML_ONEPAGECHECKOUT_STEP2_LASTNAME       = 'onepagecheckout/step_2/lastname';
    const XML_ONEPAGECHECKOUT_STEP2_COMPANY        = 'onepagecheckout/step_2/company';
    const XML_ONEPAGECHECKOUT_STEP2_ADDRESS        = 'onepagecheckout/step_2/address';
    const XML_ONEPAGECHECKOUT_STEP2_ADDRESS1       = 'onepagecheckout/step_2/address1';
    const XML_ONEPAGECHECKOUT_STEP2_CITY           = 'onepagecheckout/step_2/city';
    const XML_ONEPAGECHECKOUT_STEP2_STATE          = 'onepagecheckout/step_2/state';
    const XML_ONEPAGECHECKOUT_STEP2_ZIP            = 'onepagecheckout/step_2/zip';
    const XML_ONEPAGECHECKOUT_STEP2_COUNTRY        = 'onepagecheckout/step_2/country';
    const XML_ONEPAGECHECKOUT_STEP2_TELEPHONE      = 'onepagecheckout/step_2/telephone';
    const XML_ONEPAGECHECKOUT_STEP2_FAX            = 'onepagecheckout/step_2/fax';
    const XML_ONEPAGECHECKOUT_STEP2_SHIPPINGMETHOD = 'onepagecheckout/step_2/shippingmethod';
    const XML_ONEPAGECHECKOUT_STEP3_TITLE          = 'onepagecheckout/step_3/steptitle';
    const XML_ONEPAGECHECKOUT_STEP3_PAYMENTMETHOD  = 'onepagecheckout/step_3/paymentmethod';
    const XML_ONEPAGECHECKOUT_STEP3_ADDRESSBOOK    = 'onepagecheckout/step_3/addressbook';
    const XML_ONEPAGECHECKOUT_STEP3_ADDRESS        = 'onepagecheckout/step_3/address';
    const XML_ONEPAGECHECKOUT_STEP3_ADDRESS1       = 'onepagecheckout/step_3/address1';
    const XML_ONEPAGECHECKOUT_STEP3_CITY           = 'onepagecheckout/step_3/city';
    const XML_ONEPAGECHECKOUT_STEP3_STATE          = 'onepagecheckout/step_3/state';
    const XML_ONEPAGECHECKOUT_STEP3_ZIP            = 'onepagecheckout/step_3/zip';
    const XML_ONEPAGECHECKOUT_STEP3_COUNTRY        = 'onepagecheckout/step_3/country';
    const XML_ONEPAGECHECKOUT_STEP3_CONTACTS       = 'onepagecheckout/step_3/contacts';
    const XML_ONEPAGECHECKOUT_STEP3_ACCOUNT        = 'onepagecheckout/step_3/createacc';
    const XML_ONEPAGECHECKOUT_STEP4_TITLE          = 'onepagecheckout/step_4/steptitle';
    const XML_ONEPAGECHECKOUT_STEP4_MESSAGE        = 'onepagecheckout/step_4/message';
    const XML_ONEPAGECHECKOUT_STEP4_CANCELMESSAGE  = 'onepagecheckout/step_4/cancelmessage';
    const XML_ONEPAGECHECKOUT_STEP5_TITLE          = 'onepagecheckout/step_5/steptitle';

    public function isEnabled()
    {
        return Mage::getStoreConfigFlag(self::XML_ONEPAGECHECKOUT_ENABLED);
    }

    public function isGuestEnabled()
    {
        return Mage::getStoreConfigFlag(self::XML_PATH_GUEST_CHECKOUT);
    }

    public function isDefaultDesignEnabled()
    {
        return Mage::getStoreConfigFlag(self::XML_ONEPAGECHECKOUT_DEFAULTDESIGN);
    }

    public function isShoppinCart()
    {
        return Mage::getStoreConfigFlag(self::XML_ONEPAGECHECKOUT_CARTENABLED);
    }

    public function isSummaryEnabled()
    {
        return Mage::getStoreConfigFlag(self::XML_ONEPAGECHECKOUT_SUMMARY);
    }

    public function isWithoutLoginEnabled()
    {
        return Mage::getStoreConfigFlag(self::XML_ONEPAGECHECKOUT_NOLOGIN);
    }

    public function isLoginEnabled()
    {
        return Mage::getStoreConfigFlag(self::XML_ONEPAGECHECKOUT_LOGINCHECKOUT);
    }

    public function getStepTitle($step = 1)
    {
        return Mage::getStoreConfig('onepagecheckout/step_' . $step . '/steptitle');
    }

    public function isAddressBookEnabled($step = 2)
    {
        return Mage::getStoreConfigFlag('onepagecheckout/step_' . $step . '/addressbook');
    }

    public function isFirstnameEnabled()
    {
        return Mage::getStoreConfigFlag(self::XML_ONEPAGECHECKOUT_STEP2_FIRSTNAME);
    }

    public function isLastnameEnabled()
    {
        return Mage::getStoreConfigFlag(self::XML_ONEPAGECHECKOUT_STEP2_LASTNAME);
    }

    public function isCompanyEnabled()
    {
        return Mage::getStoreConfigFlag(self::XML_ONEPAGECHECKOUT_STEP2_COMPANY);
    }

    public function isAddressEnabled($step = 2)
    {
        return Mage::getStoreConfigFlag('onepagecheckout/step_' . $step . '/address');
    }

    public function isAddress1Enabled($step = 2)
    {
        return Mage::getStoreConfigFlag('onepagecheckout/step_' . $step . '/address1');
    }

    public function isCityEnabled($step = 2)
    {
        return Mage::getStoreConfigFlag('onepagecheckout/step_' . $step . '/city');
    }

    public function isStateEnabled($step = 2)
    {
        return Mage::getStoreConfigFlag('onepagecheckout/step_' . $step . '/state');
    }

    public function isZipEnabled($step = 2)
    {
        return Mage::getStoreConfigFlag('onepagecheckout/step_' . $step . '/zip');
    }

    public function isCountryEnabled($step = 2)
    {
        return Mage::getStoreConfigFlag('onepagecheckout/step_' . $step . '/country');
    }

    public function isTelephoneEnabled($step = 2)
    {
        return Mage::getStoreConfigFlag('onepagecheckout/step_' . $step . '/telephone');
    }

    public function isFaxEnabled($step = 2)
    {
        return Mage::getStoreConfigFlag('onepagecheckout/step_' . $step . '/fax');
    }

    public function isShippingMethodEnabled($step = 2)
    {
        return Mage::getStoreConfigFlag('onepagecheckout/step_' . $step . '/shippingmethod');
    }

    public function isPaymentMethodEnabled($step = 3)
    {
        return Mage::getStoreConfigFlag('onepagecheckout/step_' . $step . '/paymentmethod');
    }

    public function isContactsEnabled()
    {
        return Mage::getStoreConfigFlag(self::XML_ONEPAGECHECKOUT_STEP3_CONTACTS);
    }

    public function isAccountEnabled()
    {
        return Mage::getStoreConfigFlag(self::XML_ONEPAGECHECKOUT_STEP3_ACCOUNT);
    }

    public function getMessage()
    {
        return Mage::getStoreConfig(self::XML_ONEPAGECHECKOUT_STEP4_MESSAGE);
    }

    public function getCancelMessage()
    {
        return Mage::getStoreConfig(self::XML_ONEPAGECHECKOUT_STEP4_CANCELMESSAGE);
    }

    public function getSteps()
    {
        $steps = array();
        if(!Mage::helper('customer')->isLoggedIn()) {
            $steps['login'] = array('is_show' => 1,
                                    'allow'   => 1);
            $steps['shipping'] = array('is_show' => 1);
        } else {
            $steps['shipping'] = array('is_show' => 1,
                                    'allow'   => 1);
        }
            $steps['payment'] = array('is_show' => 1);
            $steps['review'] = array('is_show' => 1);
            $steps['confirm'] = array('is_show' => 1);

        return $steps;
    }

    public function getActiveStep()
    {
        return Mage::helper('customer')->isLoggedIn() ? 'shipping' : 'login';
    }

}

Answer 1

Bad naming choice in both extensions... But that's hardly your fault, so let's see what you can do.

First, think again if you really want to use both extensions. Two extensions called one page checkout are probably trying to do the same thing and will have conflicts in many other places.

If that's not the case, inheritance is indeed a possible workaround: copy the helper that's actually used to the local code pool and let it extend the other helper instead of Mage_Core_Helper_Abstract. Now all methods are available.

However, translations from the other module might not work, because a helper class is always connected to one module for translations. This is only an issue with developer mode turned on or if there are translation conflicts, so it could work for you.