Magento 2 - Error 500 when email is supposed to be triggered (we think)

Question

We have this weird issue on one of our websites.

When customers try to buy something they get an error 500 when they complete the order, the order is registered but they get an error 500 and no email is sent to the customer.

This also happens when a new customer is registering, so when they hit submit they get an error 500 and the registration is stored in Magento.

We also get error 500 in Magento when we try to click on the "reset password" button.

The reason why I think it has something to do with emails is that all of these actions should trigger an email to the customer. However, We have tested the email and it works.

This is what i get in the error logs:

==> var/log/exception.log <==

[2021-10-11 14:47:59] main.CRITICAL: Notice: Undefined index: directiveName in /chroot/home/a96f0e0b/stores.etailhandel.no/html/vendor/magento/framework/Filter/DirectiveProcessor/SimpleDirective.php on line 68 {"exception":"[object] (Exception(code: 0): Notice: Undefined index: directiveName in /chroot/home/a96f0e0b/stores.etailhandel.no/html/vendor/magento/framework/Filter/DirectiveProcessor/SimpleDirective.php on line 68 at /chroot/home/a96f0e0b/stores.etailhandel.no/html/vendor/magento/framework/App/ErrorHandler.php:61)"} []

==> ../../logs/php-error.log <==

[11-Oct-2021 14:47:59 UTC] PHP Fatal error: Uncaught TypeError: Return value of Magento\Framework\Filter\DirectiveProcessor\DependDirective::process() must be of the type string, object returned in /chroot/home/a96f0e0b/stores.etailhandel.no/html/vendor/magento/framework/Filter/DirectiveProcessor/DependDirective.php:47

Stack trace:

#0 /chroot/home/a96f0e0b/stores.etailhandel.no/html/vendor/magento/framework/Filter/Template.php(184): Magento\Framework\Filter\DirectiveProcessor\DependDirective->process(Array, Object(Magento\Email\Model\Template\Filter), Array)

#1 /chroot/home/a96f0e0b/stores.etailhandel.no/html/vendor/magento/module-email/Model/Template/Filter.php(1080): Magento\Framework\Filter\Template->filter('<!-- End Conten...')

#2 /chroot/home/a96f0e0b/stores.etailhandel.no/html/vendor/magento/module-email/Model/AbstractTemplate.php(369): Magento\Email\Model\Template\Filter->filter('<!-- End Conten...')

#3 /chroot/home/a96f0e0b/stores.etailhandel.no/html/vendor/magento/module-email/Model/AbstractTemplate.php(247): Magento\Email\Model\AbstractTempla in /chroot/home/a96f0e0b/stores.etailhandel.no/html/vendor/magento/framework/Filter/DirectiveProcessor/DependDirective.php on line 47

<!-- End Content -->
                </td>
            </tr>
            <tr>
                <td class="footer">
                    <table>
                        <tr>
                            <td>
                                <p><a href="https://cobi.no/om-cobi-norge">Om Cobi Norge</a></p>
                                <p><a href="https://cobi.no/nyheter.html">Forhandlernytt</a></p>
                            </td>
                            <td>
                                {{depend store_phone}}
                                    <p class="phone">
                                        {{trans '<a href="tel:%store_phone">%store_phone</a>' store_phone=$store_phone |raw}}
                                    </p>
                                {{/depend}}
                                {{depend store_hours}}
                                    <p class="hours">
                                        Åpningstider: <br />{{<span class="no-link">%store_hours</span>.' store_hours=$store_hours |raw}}
                                    </p>
                                {{/depend}}
                            </td>
                            <td>
                                <p class="address">
                                    Kabelgata 8<br/>
                                    0580 Oslo<br/>
                                </p>
                            </td>
                        </tr>
                    </table>
                </td>
            </tr>
        </table>
    </td>
</tr>

Answer 1

I had this same problem.

Although I don't have access to your store to evaluate your specific case, here are some hypotheses that I encountered when working through this on my own store(s).

---

Keep in mind: Template issues don't have to exist directly in your top-level email template.
The issue can manifest when a child template contains the issue that is being called-in from your top-level template.
Nonetheless: Be confident that all template issues can be resolved within Magento's Admin and do not require changes to the codebase.

---

Hypothesis #0

In the footer_template shown in your Question. There is an inconsistency.

In the first usage of {{trans ''}} regarding store_phone, it looks desired:

{{trans '<a href="tel:%store_phone">%store_phone</a>' store_phone=$store_phone |raw}}

However, in the second usage of {{trans ''}} regarding store_hours, the syntax looks malformed. It seems the opening trans ' after the opening brackets {{ is missing:

{{<span class="no-link">%store_hours</span>.' store_hours=$store_hours |raw}}

---

Hypothesis #1

You need to close your template tags!

{{depend some_var}}Some Content{{/depend}}

In my codebase, this was noticed on email templates containing {{template config_path="design/email/footer_template"}} because the footer template we created in Magento's Admin didn't close a depend tag {{depend store_phone}} with a corresponding {{/depend}}.

---

Hypothesis #2

A non-existent variable or a variable containing no data.

Although I wasn't able to test this other hypothesis at the time, I became suspicious that using a variable for which there is no data for could also cause this error even if your template tags are properly terminated. However this would be such a silly oversight by Magento that I became doubtful it could be related to the issue.

For example, I thought this could throw an error when I didn't have my phone number saved into Magento Admin's store configuration (at path general/store_information/phone):

{{depend store_phone}}
    Call us: {{store_phone}}
{{/depend}}