sure/docs/llm-guides/gating-a-preview-feature.md

Gating a preview feature

Sure ships preview features behind a single per-user toggle. Users opt in via Settings → Preferences. Opted-in users see your feature; everyone else doesn't. This guide is for hooking a new feature into the gate.

The intent is to ship in-progress work without blocking smaller PRs on a "feels finished" bar. You gate the entry points (routes, nav, anything that links into your feature) and iterate behind them. Once stable, you remove the gate in a small follow-up PR.

How the gate works

The state lives on users.preferences["preview_features_enabled"], a key inside the existing JSONB column. It defaults to false. Reading it goes through User#preview_features_enabled?.

ApplicationController includes the PreviewGateable concern, which exposes two methods to every controller:

• preview_features_enabled?. Returns a boolean. false for logged-out callers.
• require_preview_features!. A before_action helper. Redirects users without preview access to / with a flash that points them at Settings → Preferences.

The concern also registers preview_features_enabled? as a helper method, so views can call it directly.

Key files:

• app/controllers/concerns/preview_gateable.rb. The concern.
• app/models/user.rb. The preview_features_enabled? predicate.
• app/views/settings/preferences/show.html.erb. The toggle UI users see.
• app/components/DS/pill.rb. The Preview / Canary marker pill.
• config/locales/views/preview/en.yml. The redirect flash copy.

Gating a controller

Add require_preview_features! as a before_action. That's it.

class GoalsController < ApplicationController
  before_action :require_preview_features!
end

Routes stay defined; the gate runs per-request. Users without preview access hitting /goals get redirected with a flash. Preview users pass through.

If only some actions are gated, scope the before_action:

class TransactionsController < ApplicationController
  before_action :require_preview_features!, only: %i[forecast scenarios]
end

Gating a view

Wrap the relevant fragment in the helper:

<% if preview_features_enabled? %>
  <li>
    <%= link_to t(".nav.goals"), goals_path %>
  </li>
<% end %>

Same pattern works for dashboard widgets, scoreboard cards, anything that surfaces preview data alongside non-preview data. The helper resolves on every request and reflects the current user's preference.

Gating the main nav

The desktop sidebar rail and the mobile bottom nav both render from app/views/layouts/shared/_nav_item.html.erb. The partial accepts an optional preview: local — when true, it overlays a violet dot-only pill on the icon so opted-in users can tell at a glance that the rail entry leads to a preview surface.

Use the preview_gated_nav_item helper to wrap the entry. It returns nil for users without preview access (so the entry never enters the nav, once Array#compact runs) and stamps preview: true for opted-in users (so the partial paints the dot). One call, both halves of the gate:

<% mobile_nav_items = [
  { name: t(".nav.home"), path: root_path, icon: "pie-chart", icon_custom: false, active: page_active?(root_path) },
  { name: t(".nav.transactions"), path: transactions_path, icon: "credit-card", icon_custom: false, active: page_active?(transactions_path) },
  preview_gated_nav_item({ name: t(".nav.goals"), path: goals_path, icon: "piggy-bank", icon_custom: false, active: page_active?(goals_path) }),
  { name: t(".nav.assistant"), path: chats_path, icon: "icon-assistant", icon_custom: true, active: page_active?(chats_path), mobile_only: true }
].compact %>

You don't need to touch _nav_item.html.erb or set preview: true by hand. Adding a new preview nav entry is one helper call wrapped around the same hash you'd write anyway.

Marking the feature in the UI

When a preview surface renders for an opted-in user, mark it. The pill component lives in the design system:

<%# Next to a page header. The md size pairs with h1 / h2. %>
<%= render DS::Pill.new(label: "Preview", size: :md) %>

<%# Next to a sidebar nav label or section title. sm is the default. %>
<%= render DS::Pill.new(label: "Preview") %>

<%# Same shape, fuchsia tone, for canary / experimental surfaces. %>
<%= render DS::Pill.new(label: "Canary", tone: :fuchsia) %>

<%# Sidebar icon rail has no room for a label. The dot-only mode keeps the tone semantics without the text. %>
<%= render DS::Pill.new(tone: :violet, dot_only: true, title: "Preview") %>

Default tone is violet. Tones available: violet, indigo, fuchsia, amber, gray. Styles: soft (default), filled, outline. Sizes: sm (default), md. The Lookbook preview at /design-system (look for PillComponentPreview#default) flips every option, so you can see what your call site renders without a round trip to Rails.

Tests

Gated controllers should test both states. The pattern:

class GoalsControllerTest < ActionDispatch::IntegrationTest
  setup do
    sign_in @user = users(:family_admin)
  end

  test "redirects users without preview access" do
    @user.update!(preferences: (@user.preferences || {}).merge("preview_features_enabled" => false))

    get goals_url

    assert_redirected_to root_path
    assert_match(/preview/i, flash[:alert])
  end

  test "renders for users with preview access" do
    @user.update!(preferences: (@user.preferences || {}).merge("preview_features_enabled" => true))

    get goals_url

    assert_response :success
  end
end

If you write a system test, flip the preference in setup the same way before the visit.

Removing the gate when the feature ships GA

When a feature moves from preview to general availability, removing the gate is a small mechanical PR:

1. Drop the before_action :require_preview_features! line from the controller.
2. Unwrap the if preview_features_enabled? blocks in views.
3. Drop the DS::Pill markers from headers and section titles, and unwrap the preview_gated_nav_item(...) call back into a plain nav-item hash.
4. Delete the controller / view tests that exercise the redirect.

Grep for require_preview_features! and preview_features_enabled? near your feature to confirm nothing's left behind.

Notes

The flag is per-user, not per-family. Two users in the same family can see different versions of the product if one opts in and the other doesn't. That's intentional. Data is family-scoped, but visibility is a personal preference. If you write a feature that creates family-shared data (goals, budgets, etc.), the data persists when a user toggles preview off. The UI just disappears from their view while still showing up for opted-in family members.

The gate does nothing for background jobs. If your feature has a Sidekiq cron job, it runs regardless of who has preview enabled. That's usually correct (data should keep flowing), but if the job sends notifications or emails, gate those at the send site too.

The redirect target is /. If you want gated controllers to land somewhere else (a docs page, an opt-in nudge), override require_preview_features! in the controller, or write a thin custom before_action that calls preview_features_enabled? directly.