I think we should address the notice and not suppress it generally. Can you mention the notice here so that we can try how to prevent a notice somehow?

with following guides.xml config:

  <extension
            class="\phpDocumentor\Guides\Graphs\DependencyInjection\GraphsExtension"
            renderer="plantuml"
            plantuml-binary="/usr/bin/plantuml"
    />

Above the plantuml then this is rendered:

Notice: tempnam(): file created in the system's temporary directory in /opt/guides/vendor/phpdocumentor/guides-graphs/src/Graphs/Renderer/PlantumlRenderer.php on line 48

So I actually think we should suppress that notice in the graphRenderer.php of phpdocumentor, wdyt?

I think generally we do want to see PHP notices to spot errors...?!

Maybe also we're missing a php.ini setting for sys_temp_dir in our container and then the notice would not even occur....

Would you like to try to adapt your patch and actually set this sys_temp_dir to /tmp/ and see if that changes things?

Unfortunately same notice with that added to php.ini:

sys_temp_dir = /tmp