Textarea

Default

app_form_with url: "#" do |form|
  form.textarea :description
end

Autogrow

app_form_with url: "#" do |form|
  form.textarea :description, value: "Bypasses are devices that allow some people to dash from point A to point B very fast while other people dash from point B to point A very fast. People living at point C, being a point directly in between, are often given to wonder what's so great about point A that so many people from point B are so keen to get there, and what's so great about point B that so many people from point A are so keen to get there. They often wish that people would just once and for all work out where the hell they wanted to be.", autogrow: true
end

With rows

app_form_with url: "#" do |form|
  form.textarea :description, rows: 8, value: "Bypasses are devices that allow some people to dash from point A to point B very fast while other people dash from point B to point A very fast. People living at point C, being a point directly in between, are often given to wonder what's so great about point A that so many people from point B are so keen to get there, and what's so great about point B that so many people from point A are so keen to get there. They often wish that people would just once and for all work out where the hell they wanted to be."
end

Implementation

# frozen_string_literal: true

class Form::Textarea < Form::Input
  prop :rows, _Integer?, reader: :private
  prop :autogrow, _Boolean, default: false, predicate: :private, reader: :private

  def view_template
    textarea(class: classes, **options_with_defaults) do
      value
    end
  end

  private

  def default_classes = "ui-form-control"

  def default_options
    super.merge(rows:).tap do |opts|
      if autogrow?
        opts[:data] = (opts[:data] || {}).merge(
          controller: "autogrow",
          action: "input->autogrow#input"
        )
      end
    end
  end
end