I think this should be a generic solution, not just for this specific extension.

It also feels similar to this problem I tried to solve: #4124

In the meantime, that seems legit to me. @fabpot?

I think this should be a generic solution, not just for this specific extension.

It also feels similar to this problem I tried to solve: #4124

It already works for core extension, {{ obj }} is casted into string

For reminder, this PR is about html_classes only (part of html-extra), not Twig {{ stringableObject }} 🙂

It handles cases likes:
(edit)
See: #4467 (comment)

{{ html_classes(class_a, {
    (stringableObjectThatMightBeConvertedToAClass): true
}) }}

Which currently throws exception.

Can you please take a closer look at it? 🙏

I must be missing something here, but even without your patch, the new test passes. See #4506 where I've added your test without changing the code.

Sorry, the test case was the wrong one. You should get an error in the current code with:

{{ html_classes(stringableObjectThatMightBeConvertedToAClass) }}

The test fixtures have been updated accordingly.

Thank you @nlemoine.