fix(i18n): enforce cacheMaxSize: 1 on client chunk Map

Protecting both the just-written and active keys left the Map at size 2
when max was 1. Update context before setChunk so navigation sees
keep === current, and fall back to keeping only the just-written key
when the bound still cannot hold both.

Co-authored-by: Pavel Kuzmin <Virus191288@gmail.com>

Author: cursoragent

docs/guide/configuration.md

@@ -1297,7 +1297,7 @@ For most projects the default (unlimited, no expiration) is fine — route names
 `cacheMaxSize` caps:
 
 1. **Fetch / server `CacheControl`** (HTTP payload and server loader caches)
-2. **Client chunk Map** (`NuxtI18n.storage.translations`) — oldest unused `(locale, route)` chunks are evicted; the active page chunk is kept
+2. **Client chunk Map** (`NuxtI18n.storage.translations`) — oldest unused `(locale, route)` chunks are evicted; the just-written and active page keys are preferred. If the limit cannot hold both (e.g. `cacheMaxSize: 1`), the just-written key wins so the bound is enforced — active `$t` still uses the view layer
 
 - **`cacheMaxSize`** — caps entries in those caches. Useful for bounding memory.
 - **`cacheTtl`** — expires fetch/server cache entries (not the live view layer). Useful for serverless or runtime-updated translations.

docs/news/index.md

@@ -12,7 +12,7 @@ outline: 'deep'
 
 **Version**: unreleased
 
-`i18n.cacheMaxSize` already limited fetch/server `CacheControl` caches. It now also FIFO-evicts entries in the client `NuxtI18n.storage.translations` Map (`locale:route` chunks), keeping the active page. Default `0` remains unlimited — route names from Vue Router are finite, so this is an optional bound for long SPA sessions with many page dictionaries.
+`i18n.cacheMaxSize` already limited fetch/server `CacheControl` caches. It now also FIFO-evicts entries in the client `NuxtI18n.storage.translations` Map (`locale:route` chunks), preferring the active and just-written keys. When the limit cannot hold both (e.g. `1`), the just-written key wins so the bound is enforced. Default `0` remains unlimited — route names from Vue Router are finite, so this is an optional bound for long SPA sessions with many page dictionaries.
 
 ## Nuxt I18n Micro v3.26.1 — Vue DevTools live inspector
 

package.json

@@ -1,6 +1,6 @@
 {
   "name": "nuxt-i18n-micro",
-  "version": "3.27.0",
+  "version": "3.27.1",
   "description": "Fast, lightweight i18n for Nuxt with strategy-based routing and minimal overhead.",
   "keywords": [
     "i18n",

src/runtime/utils/nuxt-i18n.ts

@@ -171,7 +171,10 @@ export class NuxtI18n extends BaseI18n {
 
   /**
    * FIFO eviction for `storage.translations` when `cacheMaxSize` is set.
-   * Keeps the just-written key and the active page chunk so `$t` stays valid.
+   * Prefers keeping the just-written key and the active page chunk. When those
+   * two differ and `max` cannot hold both (e.g. `cacheMaxSize: 1`), the just-written
+   * key wins so the configured bound is always enforced. Active `$t` still resolves
+   * via `cachedTranslations` / `outgoingTranslations` even if the Map drops the old key.
    */
   private evictChunks(keep: string): void {
     const max = this.cacheMaxSize
@@ -183,6 +186,15 @@ export class NuxtI18n extends BaseI18n {
       if (key === keep || key === current) continue
       this.storage.translations.delete(key)
     }
+
+    // Protected set can exceed max when keep !== current (prefetch / seed while another
+    // page is active). Drop everything except `keep` until the bound holds.
+    if (this.storage.translations.size <= max) return
+    for (const key of this.storage.translations.keys()) {
+      if (this.storage.translations.size <= max) break
+      if (key === keep) continue
+      this.storage.translations.delete(key)
+    }
   }
 
   getLocale(): string {
@@ -238,13 +250,14 @@ export class NuxtI18n extends BaseI18n {
    * and correct for the short hot-reload window.
    */
   applySwitchContext(locale: string, routeName: string | undefined, data: Record<string, unknown>): void {
-    this.setChunk(locale, routeName, data)
-
+    // Stash / swap the view layer before setChunk so eviction sees keep === current
+    // (otherwise cacheMaxSize: 1 would protect both the old and new route keys).
     this.outgoingTranslations = this.currentLocale === locale ? this.cachedTranslations : null
     this.cachedTranslations = data
 
     this.currentLocale = locale
     this.currentRouteName = routeName || ''
+    this.setChunk(locale, routeName, data)
     triggerRef(this.contextSignal)
     this.notifyContextChange('load')
   }

test/nuxt-i18n.test.ts

@@ -173,6 +173,26 @@ describe('NuxtI18n', () => {
     expect(i18n.storage.translations.size).toBe(20)
   })
 
+  it('cacheMaxSize 1 enforces a single Map entry across navigations', () => {
+    const i18n = new NuxtI18n({ missingWarn: false, cacheMaxSize: 1 })
+
+    i18n.applySwitchContext('en', 'page-a', { title: 'A' })
+    expect(i18n.storage.translations.size).toBe(1)
+    expect(i18n.t('title')).toBe('A')
+
+    i18n.applySwitchContext('en', 'page-b', { title: 'B' })
+    expect(i18n.storage.translations.size).toBe(1)
+    expect(i18n.storage.translations.has(i18n.getCacheKey('en', 'page-b'))).toBe(true)
+    expect(i18n.t('title')).toBe('B')
+
+    // Prefetch of another route while still on page-b: just-written wins, bound stays 1.
+    i18n.setChunk('en', 'page-c', { title: 'C' })
+    expect(i18n.storage.translations.size).toBe(1)
+    expect(i18n.storage.translations.has(i18n.getCacheKey('en', 'page-c'))).toBe(true)
+    // View layer is independent of the Map eviction.
+    expect(i18n.t('title')).toBe('B')
+  })
+
   it('onContextChange reports load vs refresh reasons', () => {
     const i18n = new NuxtI18n({ missingWarn: false })
     const reasons: string[] = []