User agent exception not setting the correct templates for product pages.

[drew7721]

Preconditions

1. Magento 2.2.4
2. PHP 7.1.17
3. Redis 3.2.11
4. Mysql Ver 14.14 Distrib 5.6.39-83.1

Steps to reproduce

1. Create a parent theme ex: parent (extending or not the blank theme)
2. Create a child theme of parent for the desktop version ex: desktop
3. Create another child theme of parent for mobile devices ex: mobile
4. In all themes, create the Magento_Theme/templates/html/footer.phtml file with different content.
5. In the Admin section Content -> Design -> Configuration edit the Global Scope and set the desktop theme as default. Click Add New User Agent Rule button and add an exception for /(iPhone|iPod|iPad|Android)/i to use the mobile theme.
6. In a browser visit the site with "Responsive Design Mode" enabled and change the user agent to one one of the above. Note that the categories pages, listings and CMS pages are working fine.
7. Visit a product page. Note that the desktop footer is loading regardless of the user agent.

Expected result

What I find strange is that some templates are loading fine. For instance the header.phtml header will load proper one form the mobile theme based on the user agent but not the footer.phtml or the absolute_footer.phtml.

Actual result

1. The footer.phtml and absolute_footer.phtml templates are loading from the desktop theme instead of the mobile theme regardless of the user agent.

###Notes
For me, this has broken after upgrading to 2.2.4, on 2.1.10 it was working fine and it was loading the proper templates based on the user agent.

[drew7721]

Note that this issue seems similar and related to :

• Category design / theme update not inheriting correctly on product pages #7503
• Custom theme doesn't apply XML layout updates when applied to a product #7710
• Magento v2.1.2 - Choosing a child theme for product page #8333
• Invalid Template with Custom Theme Applied by User Agent #14932
  I've tried applying the patch in Magento v2.1.2 - Choosing a child theme for product page #8333 but it does not fix the issue.

[mbernabeu]

Hi @ drew7721 I have the same problem.

Did you find a solution to the problem?

[drew7721]

Nope, for the moment I'm not using the user agent exception anymore. I just set the mobile theme on one language and the desktop one on another language. That way I still get to test both versions without this issue breaking the page.

I don't know when this issue will be addressed. If I do find a solution I will post the update.