Buttons should support additional form* attributes

[austinw-fineart]

Description

Add support for formaction, formenctype, formmethod, formnovalidate, formtarget. These are used for button differentiation inside native forms. While you're at it, there's also the newer attributes popovertarget and popovertargetaction.

[asyncLiz]

The popover attributes are natively added to all HTML elements. You should be able to use <md-filled-button popovertarget="id-ref"> on browsers that support it today.

Those extra form attributes are used to control aspects of the <form> itself. The name and value attributes on a button are used to differentiate which button submitted the form.

Can you give more use cases for when you need these attributes on the buttons themselves? The <form>'s attributes (action, method, novalidate) should generally provide this functionality. Having individual button submissions change the behavior of a form can be a brittle implementation. Performing different logic in the form's submission itself is typically more recommended.

[austinw-fineart]

I cannot seem to get the popovertarget attribute working?
Example Playground

As for the form attributes, they've long existed for the purpose of serving good ole server-driven forms. Having multiple buttons in a form would've served for interactivity in a time before interactive UIs were a thing. You could've written up a form in as little as:

<form method="post">
  <md-outlined-text-field label="Hello" required></md-outlined-text-field>
  <md-filled-button formaction="/Search" formmethod="get">Search</md-filled-button>
  <md-filled-button formaction="/World" novalidate>World</md-filled-button>
  <md-filled-button formaction="/New">New</md-filled-button>
</form>

Yeah it's brittle, but that's what server validation is for. Are there any real world use cases? Dunno, ASP.NET certainly uses them; it's how I discovered the attributes. I just assumed these could be drop-in replacements for regular buttons so it'd be odd if this gap in support existed.

[jlesquembre]

Related: openui/open-ui#1088