fix: 🐛 fallback behaviour and simplify API contact points

example/src/routes/_layout.svelte

@@ -1,10 +1,11 @@
 <script context="module">
-  import { isLoading, waitInitialLocale } from 'svelte-i18n'
+  import { isLoading, setInitialLocale } from 'svelte-i18n'
 
   export async function preload() {
-    return waitInitialLocale({
-      default: 'en-US',
-      navigator: true,
+    return setInitialLocale({
+      fallback: 'en-US',
+      // navigator: true,
+      search: 'lang'
     })
   }
 </script>

src/client/includes/loaderQueue.ts

@@ -4,11 +4,9 @@ import {
   $dictionary,
   addMessages,
 } from '../stores/dictionary'
-import { getCurrentLocale } from '../stores/locale'
+import { getCurrentLocale, getFallbacksOf } from '../stores/locale'
 import { $isLoading } from '../stores/loading'
 
-import { getAllFallbackLocales } from './utils'
-
 type Queue = Set<MessagesLoader>
 const loaderQueue: Record<string, Queue> = {}
 
@@ -25,7 +23,7 @@ function getLocaleQueue(locale: string) {
 }
 
 function getLocalesQueues(locale: string) {
-  return getAllFallbackLocales(locale)
+  return getFallbacksOf(locale)
     .reverse()
     .map<[string, MessagesLoader[]]>(localeItem => {
       const queue = getLocaleQueue(localeItem)
@@ -35,7 +33,7 @@ function getLocalesQueues(locale: string) {
 }
 
 export function hasLocaleQueue(locale: string) {
-  return getAllFallbackLocales(locale)
+  return getFallbacksOf(locale)
     .reverse()
     .some(getLocaleQueue)
 }

src/client/includes/lookup.ts

@@ -2,8 +2,7 @@
 import resolvePath from 'object-resolve-path'
 
 import { hasLocaleDictionary } from '../stores/dictionary'
-
-import { getFallbackLocale } from './utils'
+import { getFallbackOf } from '../stores/locale'
 
 const lookupCache: Record<string, Record<string, string>> = {}
 
@@ -34,6 +33,6 @@ export const lookupMessage = (
   return addToCache(
     path,
     locale,
-    lookupMessage(dictionary, path, getFallbackLocale(locale))
+    lookupMessage(dictionary, path, getFallbackOf(locale))
   )
 }

src/client/includes/utils.ts

@@ -16,15 +16,6 @@ export function lower(str: string) {
   return str.toLocaleLowerCase()
 }
 
-export function getFallbackLocale(locale: string) {
-  const index = locale.lastIndexOf('-')
-  return index > 0 ? locale.slice(0, index) : null
-}
-
-export function getAllFallbackLocales(locale: string) {
-  return locale.split('-').map((_, i, arr) => arr.slice(0, i + 1).join('-'))
-}
-
 const getFromURL = (urlPart: string, key: string) => {
   const keyVal = urlPart
     .substr(1)
@@ -49,12 +40,11 @@ export const getClientLocale = ({
   pathname,
   hostname,
   default: defaultLocale,
+  fallback = defaultLocale,
 }: GetClientLocaleOptions) => {
   let locale
 
-  if (typeof window === 'undefined') {
-    return defaultLocale
-  }
+  if (typeof window === 'undefined') return fallback
 
   if (hostname) {
     locale = getFirstMatch(window.location.hostname, hostname)
@@ -88,5 +78,5 @@ export const getClientLocale = ({
     if (locale) return locale
   }
 
-  return defaultLocale
+  return fallback
 }

src/client/index.ts

@@ -1,22 +1,18 @@
 import merge from 'deepmerge'
 
-import { GetClientLocaleOptions, MessageObject } from './types'
-import { getClientLocale } from './includes/utils'
-import { $locale } from './stores/locale'
+import { MessageObject } from './types'
 
 // defineMessages allow us to define and extract dynamic message ids
 export function defineMessages(i: Record<string, MessageObject>) {
   return i
 }
 
-export function waitInitialLocale(options: GetClientLocaleOptions | string) {
-  if (typeof options === 'string') {
-    return $locale.set(options)
-  }
-  return $locale.set(getClientLocale(options))
-}
-
-export { $locale as locale, loadLocale as preloadLocale } from './stores/locale'
+export {
+  $locale as locale,
+  setInitialLocale,
+  // @deprecated
+  setInitialLocale as waitInitialLocale,
+} from './stores/locale'
 export {
   $dictionary as dictionary,
   $locales as locales,
@@ -26,7 +22,7 @@ export { $isLoading as isLoading } from './stores/loading'
 export { $format as format, $format as _, $format as t } from './stores/format'
 
 // utilities
-export { getClientLocale, merge }
+export { merge }
 export { customFormats, addCustomFormats } from './includes/formats'
 export {
   flushQueue as waitLocale,

src/client/stores/dictionary.ts

@@ -3,22 +3,25 @@ import { writable, derived } from 'svelte/store'
 
 import { LocaleDictionary } from '../types/index'
 
-let dictionary: LocaleDictionary
+import { getFallbackOf } from './locale'
 
+let dictionary: LocaleDictionary
 const $dictionary = writable<LocaleDictionary>({})
-$dictionary.subscribe(newDictionary => {
-  dictionary = newDictionary
-})
 
-function getDictionary() {
+export function getDictionary() {
   return dictionary
 }
 
-function hasLocaleDictionary(locale: string) {
+export function hasLocaleDictionary(locale: string) {
   return locale in dictionary
 }
 
-function addMessages(locale: string, ...partials: LocaleDictionary[]) {
+export function getAvailableLocale(locale: string): string | null {
+  if (locale in dictionary || locale == null) return locale
+  return getAvailableLocale(getFallbackOf(locale))
+}
+
+export function addMessages(locale: string, ...partials: LocaleDictionary[]) {
   $dictionary.update(d => {
     dictionary[locale] = merge.all([dictionary[locale] || {}].concat(partials))
     return d
@@ -29,10 +32,6 @@ const $locales = derived([$dictionary], ([$dictionary]) =>
   Object.keys($dictionary)
 )
 
-export {
-  $dictionary,
-  $locales,
-  getDictionary,
-  hasLocaleDictionary,
-  addMessages,
-}
+$dictionary.subscribe(newDictionary => (dictionary = newDictionary))
+
+export { $dictionary, $locales }

src/client/stores/format.ts

@@ -3,13 +3,7 @@ import { derived } from 'svelte/store'
 import { Formatter, MessageObject } from '../types'
 import { lookupMessage } from '../includes/lookup'
 import { hasLocaleQueue } from '../includes/loaderQueue'
-import {
-  getAllFallbackLocales,
-  capital,
-  upper,
-  lower,
-  title,
-} from '../includes/utils'
+import { capital, upper, lower, title } from '../includes/utils'
 import {
   getMessageFormatter,
   getTimeFormatter,
@@ -18,7 +12,7 @@ import {
 } from '../includes/formats'
 
 import { getDictionary, $dictionary } from './dictionary'
-import { getCurrentLocale, $locale } from './locale'
+import { getCurrentLocale, getFallbacksOf, $locale } from './locale'
 
 const formatMessage: Formatter = (id, options = {}) => {
   if (typeof id === 'object') {
@@ -38,7 +32,7 @@ const formatMessage: Formatter = (id, options = {}) => {
 
   if (!message) {
     console.warn(
-      `[svelte-i18n] The message "${id}" was not found in "${getAllFallbackLocales(
+      `[svelte-i18n] The message "${id}" was not found in "${getFallbacksOf(
         locale
       ).join('", "')}". ${
         hasLocaleQueue(getCurrentLocale())

src/client/stores/locale.ts

@@ -1,30 +1,54 @@
 import { writable } from 'svelte/store'
 
-import { getFallbackLocale, getAllFallbackLocales } from '../includes/utils'
 import { flushQueue, hasLocaleQueue } from '../includes/loaderQueue'
+import { getClientLocale } from '../includes/utils'
+import { GetClientLocaleOptions } from '../types'
 
-import { getDictionary } from './dictionary'
+import { getAvailableLocale } from './dictionary'
 
+let fallback: string = null
 let current: string
 const $locale = writable(null)
 
-function getCurrentLocale() {
-  return current
+export function getFallbackLocale() {
+  return fallback
+}
+
+export function setfallbackLocale(locale: string) {
+  fallback = locale
+}
+
+export function isFallbackLocaleOf(localeA: string, localeB: string) {
+  return localeB.indexOf(localeA) === 0
+}
+
+export function getFallbackOf(locale: string) {
+  const index = locale.lastIndexOf('-')
+  if (index > 0) return locale.slice(0, index)
+  if (fallback && !isFallbackLocaleOf(locale, fallback)) return fallback
+  return null
 }
 
-function getAvailableLocale(locale: string): string | null {
-  if (locale in getDictionary() || locale == null) return locale
-  return getAvailableLocale(getFallbackLocale(locale))
+export function getFallbacksOf(locale: string): string[] {
+  const locales = locale
+    .split('-')
+    .map((_, i, arr) => arr.slice(0, i + 1).join('-'))
+
+  if (fallback != null && !isFallbackLocaleOf(locale, fallback)) {
+    return locales.concat(getFallbacksOf(fallback))
+  }
+  return locales
+}
+
+function getCurrentLocale() {
+  return current
 }
 
-function loadLocale(localeToLoad: string) {
-  return Promise.all(
-    getAllFallbackLocales(localeToLoad).map(localeItem =>
-      flushQueue(localeItem)
-        .then(() => [localeItem, { err: undefined }])
-        .catch(e => [localeItem, { err: e }])
-    )
-  )
+export function setInitialLocale(options: GetClientLocaleOptions) {
+  if (typeof options.fallback === 'string') {
+    setfallbackLocale(options.fallback)
+  }
+  return $locale.set(getClientLocale(options))
 }
 
 $locale.subscribe((newLocale: string) => {
@@ -37,17 +61,13 @@ $locale.subscribe((newLocale: string) => {
 
 const localeSet = $locale.set
 $locale.set = (newLocale: string): void | Promise<void> => {
-  if (getAvailableLocale(newLocale)) {
-    if (hasLocaleQueue(newLocale)) {
-      return flushQueue(newLocale).then(() => localeSet(newLocale))
-    }
-    return localeSet(newLocale)
+  if (getAvailableLocale(newLocale) && hasLocaleQueue(newLocale)) {
+    return flushQueue(newLocale).then(() => localeSet(newLocale))
   }
-
-  throw Error(`[svelte-i18n] Locale "${newLocale}" not found.`)
+  return localeSet(newLocale)
 }
 
 $locale.update = (fn: (locale: string) => void | Promise<void>) =>
   localeSet(fn(current))
 
-export { $locale, loadLocale, flushQueue, getCurrentLocale }
+export { $locale, flushQueue, getCurrentLocale }

test/client/index.test.ts

@@ -4,13 +4,12 @@ import {
   dictionary,
   locale,
   format,
-  getClientLocale,
   addCustomFormats,
   customFormats,
-  preloadLocale,
   register,
   waitLocale,
 } from '../../src/client'
+import { getClientLocale } from '../../src/client/includes/utils'
 
 global.Intl = require('intl')
 
@@ -42,19 +41,9 @@ describe('locale', () => {
     await locale.set('en-US')
     expect(currentLocale).toBe('en-US')
   })
-
-  it("should throw an error if locale doesn't exist", () => {
-    expect(() => locale.set('FOO')).toThrow()
-  })
 })
 
 describe('dictionary', () => {
-  it('load a locale and its derived locales if dictionary is a loader', async () => {
-    const loaded = await preloadLocale('pt-PT')
-    expect(loaded[0][0]).toEqual('pt')
-    expect(loaded[1][0]).toEqual('pt-PT')
-  })
-
   it('load a partial dictionary and merge it with the existing one', async () => {
     await locale.set('en')
     register('en', () => import('../fixtures/partials/en.json'))
@@ -96,7 +85,8 @@ describe('formatting', () => {
     expect(_({ id: 'switch.lang' })).toBe('Switch language')
   })
 
-  it('should translate to passed locale', () => {
+  it('should translate to passed locale', async () => {
+    await waitLocale('pt-BR')
     expect(_('switch.lang', { locale: 'pt' })).toBe('Trocar idioma')
   })