FWIW, while the Codex Field component differentiates the label text and description text for fieldsets, they are both contained within the <legend> element - in my research, I found that this was the only reliable way to ensure that, when you tab into a fieldset, both the label and description are read to you. I still think this task needs to be done to allow you to pass in separate things for label, optional flag, and description, I just wanted to make this note about the resulting markup.

@Catrope I want to clarify what this task covers. I see 3 distinct things that could have descriptions and optional flags:

• HTMLForm sections, which are outputs as <fieldset>s
• HTMLFormFields
• HTMLFormFields that are fieldsets, e.g. a group of radios (is there even a concept of this, or are fieldsets only used as sections?)

Does this task only cover the first one? Do we need to cover the other two in a separate task?

In T359016#9640031, @AnneT wrote:

@Catrope I want to clarify what this task covers. I see 3 distinct things that could have descriptions and optional flags:

• HTMLForm sections, which are outputs as <fieldset>s
• HTMLFormFields
• HTMLFormFields that are fieldsets, e.g. a group of radios (is there even a concept of this, or are fieldsets only used as sections?)

There isn't, fieldsets are only used as sections. I'm open to suggestions for handling this differently, but I think the best way to fit our Field component in the mold of how HTMLForm wants to structure its forms is probably to use fieldsets for sections, and non-fieldset Fields for each HTMLFormField (both single input fields and compound fields).

Does this task only cover the first one? Do we need to cover the other two in a separate task?

That's a great question, I hadn't considered this. The new design for Special:Block only applies descriptions and optional tags to sections (fieldsets), but I think that's in part because Special:Block (ab)uses sections to create fieldsets, in such a way that most sections only contain one field (or a group of checkboxes). For now, I think it makes the most sense to just do descriptions for fieldsets (#1), and leave descriptions for individual fields (#2) for later, if we ever need it. (Most existing HTMLForm designs appear to work around the lack of descriptions by making more use of help texts instead.)

Change 1012441 had a related patch set uploaded (by Anne Tomasevich; author: Anne Tomasevich):

[mediawiki/core@master] CodexHTMLForm: Add support for fieldset and legend

https://gerrit.wikimedia.org/r/1012441

Change #1012441 merged by jenkins-bot:

[mediawiki/core@master] CodexHTMLForm: Add support for fieldset, description, and optional

https://gerrit.wikimedia.org/r/1012441