Magento2: [Issue] Fixed 'Undefined class constant' error when interceptor is generated.

[m2-assistant[bot]]

This issue is automatically created based on existing pull request: magento/magento2#28797: Fixed 'Undefined class constant' error when interceptor is generated.

---

Summary (*)

1. Magento 2.4-develop
2. Since constant is declared as private it's not accessible from parent classes.
3. Since it used with static keyword, PHP will search it within class instance.
4. Class instance will be an instance of generated Interceptor without access to private variables of child classes.
5. This will lead to an 'Undefined class constant' error.

Examples (*)

1. Create a plugin for Magento\Theme\Block\Html\Title class:

   <type name="Magento\Theme\Block\Html\Title">
       <plugin name="titlePlugin" type="Magento\Theme\Plugin\TitlePlugin" />
   </type>
   

   <?php
   
   namespace Magento\Theme\Plugin;
   
   class TitlePlugin
   {
       /**
        * @param mixed $subject
        * @param mixed $result
        * @return mixed
        */
       public function afterGetPageHeading(
           $subject,
           $result
       ) {
           return $result;
       }
   }
   

2. Open frontend.

3. You'll see an error:

   Error: Undefined class constant 'XML_PATH_HEADER_TRANSLATE_TITLE' in app/code/Magento/Theme/Block/Html/Title.php:104 
   Stack trace: 
   #0 app/code/Magento/Theme/Block/Html/Title.php(82): Magento\Theme\Block\Html\Title->shouldTranslateTitle() 
   #1 generated/code/Magento/Theme/Block/Html/Title/Interceptor.php(32): Magento\Theme\Block\Html\Title->getPageHeading() 
   #2 app/code/Magento/Theme/view/frontend/templates/html/title.phtml(12): Magento\Theme\Block\Html\Title\Interceptor->getPageHeading()
   ...
   

Proposed solution

Another way to solve this bug - is to declare constant as public instead of private.
If you think it should be public - I'll update PR.

[m2-assistant[bot]]

Hi @engcom-Delta. Thank you for working on this issue.
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[magento-engcom-team]

:white_check_mark: Confirmed by @engcom-Delta
Thank you for verifying the issue. Based on the provided information internal tickets MC-35619 were created

Issue Available: @engcom-Delta, _You will be automatically unassigned. Contributors/Maintainers can claim this issue to continue. To reclaim and continue work, reassign the ticket to yourself._

[motorlesha]

we have the same issue. Please fix it

[magento-engcom-team]

Hi @m2-assistant[bot]. Thank you for your report.
The issue has been fixed in magento/magento2#28797 by @vovayatsyuk in 2.4-develop branch
Related commit(s):

• 54531b3a57aa6828c4a84c4ac4d330dbbe102e63
• 1785136c5911b792503b7e69f636c6cc6c1ced56
• 7620af2c904a86d4e697026d0bdd4bd85f6ccac1
• dbad97bd5c0f4c46c3329f7b87f662292b2e3945

The fix will be available with the upcoming 2.4.1 release.

[alexey-motorny-amasty]

@magento-engcom-team why fatal error will be included only in 2.4.1 version? This is a critical error. Is any chance to include this fix into 2.4.0 version? Safe fix

[Hexmage]

I don't understand how 2.4.0 could be released with this error in it which basically just crashes every frontend page.

[alexey-motorny-amasty]

@Hexmage we have created patch - mini module to resolve this error. Maybe it will be useful for you
https://amasty.com/knowledge-base/magento-2-4-release-undefined-class-constant-error.html

[hostep]

@alexey-motorny-amasty: out of interest (since I saw your little amasty/module-mage24fix module come in with composer when updating the improved layered navigation module on a 2.3.5 shop). This little module is tested and is backwards compatible with Magento 2.3.x I hope?

[alexey-motorny-amasty]

@hostep Yes, it is compatible, but unnecessary. do not hesitate to just delete this patch

[mdehaan]

@Hexmage we have created patch - mini module to resolve this error. Maybe it will be useful for you
https://amasty.com/knowledge-base/magento-2-4-release-undefined-class-constant-error.html

Hi Hexmage, I have a problem with your this fix: #48 {main} [] []
[2020-08-14 13:30:16] main.CRITICAL: Error: Class 'Amasty\Mage24Fix\Block\Theme\Html\Title' not found in /public_html/generated/code/Amasty/Mage24Fix/Block/Theme/Html/Title/Interceptor.php:7

[Hexmage]

@mdehaan not my fix contact @alexey-motorny-amasty instead.

[alexey-motorny-amasty]

@mdehaan please check if you have copied all the files. or run setup:di:compile

[mdehaan]

@mdehaan please check if you have copied all the files. or run setup:di:compile
@alexey-motorny-amasty

I just fixed it.
I renamed module-mage24fix-master to Mage24Fix and now it works.

[magento-engcom-team]

Hi @m2-assistant[bot]. Thank you for your report.
The issue has been fixed in magento/magento2#29925 by @toxix in 2.4-develop branch
Related commit(s):

• 2d1d097b39bdd94ef6e929c34fc721113a3505ea

The fix will be available with the upcoming 2.4.2 release.