After examining the available form validation libraries, I come to the conclusion that a custom Form component would be the cleanest way of form validation with SvelteUI.

The TextInput field could integrate the on:blur, on:change, on:input event handlers, the bind:value, and the error message using the context API.

I would recommend schema based validation with Zod. For more advanced use cases, a custom validation function could be specified.

<script>
  import { Form, TextInput } from '@svelteuidev/core';
  import * as zod from 'zod';

  const mySchema = z.object({
    username: z.string(),
    password: z.string(),
  };
</script>
<Form schema={mySchema}>
  <TextInput name="username"/>
  <TextInput name="password" type="password"/>
</Form>

Do you want to contribute this feature and create a pull request

Yes