Alt text is not inserted (nor available to template) with core image field

IDK if this is your issue, but if you have "Apply caption to images" on for the insert widget settings on that field your alt/title values get overwritten by this code in the template:

{% if insert_settings.caption %}
  {% set attach = attach|merge({attributes: {'data-caption': ['title']}}) %}
{% endif %}

I'm unable to reproduce the issue setting up a fresh Drupal 9.1.5 instance with just the Insert module installed. Content type has a basic image field with Insert enabled to insert original image and alt field required. Inserting the image into the body and saving the node results in the alt attribute being rendered in the HTML on the image tag.

It's been a while since I have dealt with the code, but the alt attribute should be applied using the CKE image widget as that allows editing image attributes per the image button in the editor toolbar. There is no alt variable passed to the insert-image.html.twig template, so I would not expect {{ alt }} to output anything—that is expected behaviour.

If the alt attribute is not rendered in the HTML output, please provide the exact Drupal core version you are using and the exact steps to reproduce. It would be awesome if you could also check if you would have the issue on a fresh clean Drupal installation with just the Insert module installed to check if there might be some conflict with one of your other modules installed.

I'm sorry for like taking months on this to get back… finally having a day off. I could see this issue might be outdated by now, but was still interested looking at this again, though I don't expect an answer as it's months ago.

I cannot reproduce on a plain textarea either. I even uninstalled the CKEditor module. Rolled things up again stepping through the code… there could be multiple places where some Insert module config might just be mixed up. After all, it would be great to see what is actually inserted in the textarea as that might give some hint on what might be missing. The data-insert-attach attribute being present is vital as that defines where to pick up the alt text from—the values of data-insert-attach are internally mapped to jQuery selectors.

Generally, the alt text is purely handled by JavaScript, which is retrieving the alt text value per jQuery from the alt text input. Potentially, there could be something going wrong in JavaScript causing a JS error to appear in the browser's dev console when inserting the image.

It would be nice to step into the code with the dev tools debugger and see if the alt input is actually picked up by the code as per https://git.drupalcode.org/project/insert/-/blob/8.x-2.x/js/ImageHandler.... this._$altField should be assigned a reference to the alt input. If not, need to check why the selector 'input[name$="[alt]"], textarea[name$="[alt]"]' is not picking up the alt input.

There are image styles which prevent the alt text from being inserted (link and icon_link), but since original is being used, that should ne be an issue.

Feel free to reopen if still relevant.