Render error message for hidden field

Hello! I have a hidden input and I’m using buttons to set it’s value. The default value for this field is nil. If a user doesn’t select one of the options, I would like to show the error from the changeset beneath the buttons, like with other form fields that have automatic error handling. How can this be done?

I’ve seen references to an error_tag, but such a tag no longer exists as far as I can tell?


Before Phoenix 1.7 error_tag was a function defined for you in the ErrorHelpers module (source).

Since 1.7 there is a CoreComponents module. If has an <.input /> component that renders an input field with error feedback using <.error />. So you could use that:

<.input field={@form[:some_field]} type="hidden" />

This will generate a hidden input field and the error feedback.

If you’d rather display the error yourself you can just access it directly: @form[:some_field].errors and render it as you like.

The Phoenix Form Bindings guide discusses using phx-feedback attribute for styling and hiding error messages.

Updated: Just noticed LiveView 1.0 will drop support for phx-feedback.

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Oh, that’s awesome. That actually works great, idk why I didn’t think of that :sweat_smile:

After implementing this, it does work but I’m also getting warnings in the console about it. Do you just ignore them? Lol

     warning: attribute "type" in component NuzzleWeb.CoreComponents.input/1 must be one of ["checkbox", "color", "date", "datetime-local", "email", "file", "month", "number", "password", "range", "search", "select", "tel", "text", "textarea", "time", "url", "week"], got: "hidden"
 142 │             <.input type="hidden" field={@form[:gender]} />
     │             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     └─ lib/nuzzle_web/live/quote.ex:142: (file)

<.input> bundles a bunch of markup around labels and errors together, which doesn’t really make sense for hidden inputs. You can just use a normal input and the <.error> component separately.

Are you aware of an example somewhere that shows what this would look like?
The only example I have come across with the <.error> component is this, which doesn’t seem relevant for showing errors for a single input:
<.error :for={msg <- @errors}><%= msg %></.error>

Not sure how this wouldn’t seem relevant, but if you follow what happens as part of <.input> it would show that it does the following eventually:

<.error :for={msg <-[:gender].errors, &translate_error(&1)}><%= msg %></.error>