Field

Groups a label, a control, a description and an error message, and owns the validity state they all read.

Wrap a control in Field and it picks up a label, a description, an error message and the validity state behind them. Reach for it whenever a control needs a name, a hint, or something to say when the value is wrong.

Username

Three characters or more. Validated when you leave the field.

App.vue

<template>
  <Field.Root
    class="group flex w-[17rem] flex-col gap-1.5"
    :options="{ name: 'username', validate: validateUsername }"
  >
    <div :class="box">
      <div :class="stack">
        <span :class="line">
          <Input
            v-model="username"
            :class="control"
            placeholder=" "
            autocomplete="off"
          />
        </span>
        <Field.Label :class="label">Username</Field.Label>
      </div>
    </div>

    <Field.Description :class="hint">
      Three characters or more. Validated when you leave the field.
    </Field.Description>

    <Field.Error v-slot="{ messages }" :class="error">
      {{ messages.join(' ') }}
    </Field.Error>
  </Field.Root>
</template>

<script setup lang="ts">
import { ref } from 'vue'
import { Field } from '@maas/mirror/vue/Field'
import { Input } from '@maas/mirror/vue/Input'

const username = ref('')

const box = [
  'relative isolate flex h-12 w-full cursor-text items-center justify-between gap-1.5',
  'rounded-component-lg border-surface border-2 px-[0.875rem]',
  'transition-all duration-100 ease-linear [&_*]:transition-all [&_*]:duration-100 [&_*]:ease-linear',
  'outline-4 outline-transparent focus-within:focus-ring',
  'group-[[data-invalid=true]:not([data-focused=true])]:border-danger-subtle',
  'group-[[data-invalid=true]:not([data-focused=true])]:bg-danger-subtle',
  'group-data-[disabled=true]:border-disabled-subtle group-data-[disabled=true]:cursor-not-allowed',
].join(' ')

const stack = [
  'group/stack flex h-full max-h-full w-full flex-col-reverse',
  'items-center justify-center gap-0 px-1',
  'focus-within:gap-1 has-[input:not(:placeholder-shown)]:gap-1',
].join(' ')

const line = [
  'relative flex h-0 w-full items-end',
  'group-focus-within/stack:h-[0.9375rem]',
  'has-[input:not(:placeholder-shown)]:h-[0.9375rem]',
].join(' ')

const control = [
  'type-component-lg leading-[normal]! text-surface',
  'block box-content h-[1lh] w-full py-1.25 -my-1.25 appearance-none bg-transparent outline-none',
  'placeholder:text-transparent',
  'group-[[data-invalid=true]:not([data-focused=true])]:text-danger-on-muted',
  'data-[disabled=true]:text-disabled-solid',
].join(' ')

const label = [
  'type-component-lg leading-[normal]! text-surface-muted',
  'flex h-full w-full items-center [--mirror-label-cursor:text]',
  "before:absolute before:-inset-0.5 before:-z-10 before:content-['']",
  'group-focus-within/stack:h-auto group-focus-within/stack:text-[0.6875rem] group-focus-within/stack:[--mirror-label-cursor:auto]',
  'group-has-[input:not(:placeholder-shown)]/stack:h-auto group-has-[input:not(:placeholder-shown)]/stack:text-[0.6875rem] group-has-[input:not(:placeholder-shown)]/stack:[--mirror-label-cursor:auto]',
  'group-[[data-invalid=true]:not([data-focused=true])]:text-danger-muted',
  'group-data-[disabled=true]:text-disabled-muted',
].join(' ')

const hint = 'type-component-2xs text-surface-muted'
const error = 'type-component-2xs text-danger-muted'

function validateUsername(value: unknown) {
  const entry = String(value ?? '')

  if (entry.length === 0) {
    return 'Enter a username.'
  }

  return entry.length < 3 ? 'Use at least three characters.' : null
}
</script>

Show code

Usage guidelines

Only one control may register per field, since it owns data-focused and the aria-describedby chain, and a second one throws duplicate_field_control.must
A control reports its initial value as it registers, which counts as a change, so onChange validation leaves an empty required field invalid before the user has touched it. We default to onBlur for that reason.should
Give a second Field.Description or Field.Error its own id, or both take the field’s generated ID and aria-describedby lists it once.must
In onSubmit mode the browser blocks its own submit event while a native control fails a constraint, so the field never hears it. Wrap the fields in Form, which sets novalidate for you, or set novalidate on your own <form>.must