Add the option to make the textarea required

[metamoni]

<trix-editor> currently accepts autofocus and placeholder attributes, but not a required attribute. It would be useful to add this in, to get the basic validation mechanism that HTML provides.

At the moment we're relying on Active Record validation to prevent users from submitting a form without filling in this field. We also have to add aria-required="true" to notify screen reader users.

Steps to Reproduce

1. Create a rich text area with required: true: <%= f.rich_text_area :about, class: "dm--input", required: true %>
2. Try to submit the form without filling it out
3. Notice that there's no HTML validation

Details

• Trix Rails version: 7.1.3
• Browser name and version: Chrome version 123.0.6312.59 (Official Build) (arm64)
• Operating system: MacOS 14.4

[seanpdoyle]

I consider this issue to overlap with #1023 and #1128.

While #1128 does not add support for the [required] attribute, it does set the foundation for follow ups to integrate with ElementInternals.validity.

[afcapel]

I agree with @seanpdoyle, the way to go is through ElementInternals so the custom element can take part in the form validation.