Present code not autoloading, class not found (clear composer-managed code PHP cache)

This was the best answer it turns out (i tried it independently, but saw it on closing tabs):

In answer to

Similar symptoms, probably different cause:

Cached autoloader misses cause failures when missed class becomes available

Cached ClassMap entries not reset after registering new prefix

How one iteration manifested

I am using lando with the pantheon recipe and trying to install a composer library. The library is installed via composer, but when I try to use it in a custom Drupal module, it throws an error that the class cannot be found. Regular drupal modules required via composer work fine. Have seen something similar?

I did not know how to configure DDEV to play nice with Pantheon

And Lando has a recipe that seems to work

but this one dependency is breaking the whole thing

I see the dependency in /vendor, but it is not being loaded

I assume it has something to do with the autoloader

But no clue how to fix it

@problemhaver did you just add it? Have you tried restarting the VM? (or just the php service, then drush cr)

I will stop and start the project, but that has not been needed so far

after restarting the project I get a different error. LOL

while testing, I had bump to a newer version of the library. After downgrading to the one used in the existing site it works now. Thanks!

Having to restart the project seems like a weird solution, but I remember sometime ago I spent too much time trying to debug a problem and it was solved after restarting DDEV. Who knows.

mlncn: it’s the PHP autoload stuff, like you said. PHP is all that technically needs to be restarted.