@molecule/app-version

Version and update management interface for molecule.dev.

Tracks the running build, polls a same-origin /version.json for new deploys, manages the service-worker update lifecycle (waiting worker, skip-waiting, reload), and emits events. Headless: the app owns the "update available" banner/toast — styled via getClassMap() and translated via t() — while this package owns detection, apply, and dismiss.

Auto-generated, AI-first package reference for the molecule.dev ecosystem. It is written to be read by coding agents as much as by people, and is generated from this package's source — edit src/index.ts JSDoc, not this file.

Quick Start

import {
  applyUpdate,
  getProvider,
  setCurrentVersion,
  startPeriodicChecks,
} from '@molecule/app-version'

// At startup — build-time values injected by the bundler:
setCurrentVersion({ buildId: __BUILD_ID__, version: __APP_VERSION__ })
startPeriodicChecks({ immediate: true }) // polls /version.json (default: every 5 min)

// Render your own update UI from events:
getProvider().on('update-available', () => {
  showUpdateBanner({ onReload: () => applyUpdate() })
})

Type

core

Installation

npm install @molecule/app-version @molecule/app-bond @molecule/app-i18n @molecule/app-logger

API

Interfaces

ServiceWorkerTemplateOptions

Options for generating the service worker template.

interface ServiceWorkerTemplateOptions {
  /**
   * Whether to include push notification handlers.
   * @default false
   */
  pushNotifications?: boolean

  /**
   * Maximum number of cached images.
   * @default 50
   */
  maxImageCacheEntries?: number

  /**
   * Additional file extensions to cache (besides .png).
   * @default []
   */
  imageCacheExtensions?: string[]
}

VersionInfo

Static build metadata (version string, build ID, commit hash, branch, timestamp).

interface VersionInfo {
  /**
   * Build ID (e.g., from CI/CD).
   */
  buildId: string

  /**
   * Semantic version string.
   */
  version: string

  /**
   * Build timestamp.
   */
  buildTime?: string

  /**
   * Git commit hash.
   */
  commitHash?: string

  /**
   * Git branch.
   */
  branch?: string
}

VersionState

Reactive version state including current build info, update availability, and checking status.

interface VersionState extends VersionInfo {
  /**
   * New build ID if update detected.
   */
  newBuildId?: string

  /**
   * New version if update detected.
   */
  newVersion?: string

  /**
   * Whether a new version is available.
   */
  isUpdateAvailable: boolean

  /**
   * Whether a new service worker is waiting.
   */
  isServiceWorkerWaiting: boolean

  /**
   * Last check timestamp.
   */
  lastChecked?: Date

  /**
   * Whether currently checking for updates.
   */
  isChecking: boolean
}

ServiceWorkerController

Service worker registration with update capability.

interface ServiceWorkerController {
  /**
   * Registers the service worker.
   */
  register(scriptUrl?: string): Promise<ServiceWorkerRegistration | null>

  /**
   * Unregisters the service worker.
   */
  unregister(): Promise<boolean>

  /**
   * Checks for service worker updates.
   */
  update(): Promise<void>

  /**
   * Skips waiting and activates new service worker.
   */
  skipWaiting(): void

  /**
   * Gets the current registration.
   */
  getRegistration(): ServiceWorkerRegistration | null

  /**
   * Gets the waiting service worker.
   */
  getWaiting(): ServiceWorker | null

  /**
   * Checks if a service worker is waiting.
   */
  isWaiting(): boolean

  /**
   * Posts a message to the service worker.
   */
  postMessage(message: unknown): void
}

UpdateCheckOptions

Update check options.

interface UpdateCheckOptions {
  /**
   * URL to check for version info.
   */
  versionUrl?: string

  /**
   * Interval in milliseconds between checks.
   */
  interval?: number

  /**
   * Whether to check immediately on start.
   */
  immediate?: boolean
}

VersionProvider

Version provider interface that all version bond packages must implement. Manages version tracking, update detection, and service worker lifecycle.

interface VersionProvider {
  /**
   * Gets the current version state.
   */
  getState(): VersionState

  /**
   * Sets the current version info.
   */
  setCurrentVersion(info: VersionInfo): void

  /**
   * Checks for updates.
   */
  checkForUpdates(): Promise<boolean>

  /**
   * Starts periodic update checks.
   */
  startPeriodicChecks(options?: UpdateCheckOptions): void

  /**
   * Stops periodic update checks.
   */
  stopPeriodicChecks(): void

  /**
   * Gets the service worker controller.
   */
  getServiceWorker(): ServiceWorkerController

  /**
   * Applies the update (reloads the page).
   */
  applyUpdate(options?: { force?: boolean }): void

  /**
   * Dismisses the update notification.
   */
  dismissUpdate(): void

  /**
   * Subscribes to version events.
   */
  on<T>(event: VersionEvent, handler: VersionEventHandler<T>): () => void

  /**
   * Unsubscribes from events.
   */
  off<T>(event: VersionEvent, handler: VersionEventHandler<T>): void

  /**
   * Destroys the provider.
   */
  destroy(): void
}

Types

VersionEvent

Version lifecycle events emitted during update checks and service worker transitions.

type VersionEvent =
  | 'update-available'
  | 'service-worker-waiting'
  | 'service-worker-activated'
  | 'check-start'
  | 'check-complete'
  | 'check-error'

VersionEventHandler

Callback for version events. Receives event-specific data.

type VersionEventHandler<T = unknown> = (data: T) => void

• data — Event payload (varies by event type).

Functions

createVersionChecker(getState, updateState, emit)

Creates a version checker.

function createVersionChecker(
  getState: () => VersionState,
  updateState: (partial: Partial<VersionState>) => void,
  emit: <T>(event: VersionEvent, data: T) => void,
): () => Promise<boolean>

• getState — Function to get the current version state.
• updateState — Function to update the version state.
• emit — Function to emit events.

Returns: The check for updates function.

createWebVersionProvider()

Creates a browser-based version provider that checks for updates by polling a /version.json endpoint, manages a service worker for cache invalidation, and emits events when updates are available.

function createWebVersionProvider(): VersionProvider

Returns: A fully configured VersionProvider for browser environments.

setProvider(provider)

Registers a version provider as the active singleton.

function setProvider(provider: VersionProvider): void

• provider — The version provider implementation to bond.

getProvider()

Retrieves the bonded version provider. If none is bonded, automatically creates a browser-based version provider.

function getProvider(): VersionProvider

Returns: The active version provider instance.

getState()

Returns the current version state snapshot (build ID, version string, update availability, service worker status).

function getState(): VersionState

Returns: A copy of the current VersionState.

setCurrentVersion(info)

Sets the current application version info. Typically called at startup with build-time values injected by the bundler.

function setCurrentVersion(info: VersionInfo): void

• info — Build metadata including version, buildId, and optional commitHash.

Returns: Nothing.

checkForUpdates()

Checks for application updates by fetching /version.json and comparing the remote build ID against the current one.

function checkForUpdates(): Promise<boolean>

Returns: true if an update is available.

startPeriodicChecks(options)

Starts periodic update checks at the specified interval.

function startPeriodicChecks(options?: UpdateCheckOptions): void

• options — Check interval and whether to run an immediate check on start.

Returns: Nothing.

stopPeriodicChecks()

Stops periodic update checks started by startPeriodicChecks().

function stopPeriodicChecks(): void

Returns: Nothing.

getServiceWorker()

Returns the service worker controller for managing cache invalidation and skip-waiting lifecycle events.

function getServiceWorker(): ServiceWorkerController

Returns: The ServiceWorkerController instance.

applyUpdate(options)

Applies a pending update by activating a waiting service worker (if present) and reloading the page. If no service worker is waiting, reloads the page when an update is available or force is set.

function applyUpdate(options?: { force?: boolean }): void

• options — Pass { force: true } to reload even without a detected update.
• options.force — Whether to force a reload regardless of update status.

Returns: Nothing.

dismissUpdate()

Dismisses the current update notification by clearing the isUpdateAvailable flag in state.

function dismissUpdate(): void

Returns: Nothing.

generateServiceWorkerTemplate(options)

Generates a service worker TypeScript source file.

function generateServiceWorkerTemplate(options?: ServiceWorkerTemplateOptions): string

• options — Template configuration options.

Returns: The service worker source code as a string.

createServiceWorkerController(updateState, emit)

Creates a service worker controller.

function createServiceWorkerController(
  updateState: (partial: Partial<VersionState>) => void,
  emit: <T>(event: VersionEvent, data: T) => void,
): { controller: ServiceWorkerController; getRegistration: () => ServiceWorkerRegistration | null }

• updateState — Function to update the version state.
• emit — Function to emit events.

Returns: The service worker controller.

Constants

DEFAULT_CHECK_INTERVAL

Default version check interval (5 minutes).

const DEFAULT_CHECK_INTERVAL: number

DEFAULT_VERSION_URL

Default version URL.

const DEFAULT_VERSION_URL: '/version.json'

Injection Notes

Requirements

Peer dependencies:

• @molecule/app-bond ^1.0.1
• @molecule/app-i18n ^1.0.1
• @molecule/app-logger ^1.0.1

Runtime Dependencies

• @molecule/app-bond

• @molecule/app-i18n

• @molecule/app-logger

• No bond wiring needed on the web. getProvider() auto-creates a browser-based provider on first access; call setProvider() only to substitute a custom/native implementation.

• Update detection has TWO prerequisites this package does not create: (1) setCurrentVersion() must run at startup with real build-time values — the checker only reports an update when the CURRENT buildId/version is non-empty and differs from the remote; (2) the app must serve /version.json (same-origin, VersionInfo shape: { buildId, version, … }) and regenerate it on every deploy. Miss either and checks silently never find an update.

• applyUpdate() reloads the page (activating a waiting service worker first when present). Surface the update-available event in UI and let the user opt in — never call it unprompted; unsaved state is lost on reload.

• service-worker-template.ts generates service-worker SOURCE at scaffold time (precache + push handlers); it is not a runtime service worker itself.

Translations

Translation strings are provided by @molecule/app-locales-version.