perf(l10n): cache literal (no-arg) translations

Add a locale-keyed cache for no-argument translation lookups so repeated
literal keys resolve without redoing the lookup chain. Reset on locale change
and on locale override application.

Ported from phase3-measured-perf (cherry-pick -x 970dd88), adapted to current
main (hoisted the per-locale cache-table creation; excludes the branch's audit
doc and gitignored test).

CHANGELOG.md

@@ -9,6 +9,12 @@
 - **[Lua 5.0 - Modulo Operator]** Routed the nine arithmetic `%` modulo sites (daily/weekly quest flag tests, Darkmoon Faire cycle math, learner GUID/flag math, race/class flag tests) through the existing `math.mod` shim. Lua 5.0 has no `%` operator outside string formatting, so this was a parse error on Vanilla 1.12 clients; the addon now parses on 5.0 through Retail.
 - **[Lua 5.0 - Options Tab Tables]** Fixed `QuestieOptions.tabs.{auto,dbm,icons,nameplate}` being initialized with `{...}` instead of `{}`. On Lua 5.1 this silently captured the addon varargs into the table; on Lua 5.0 it is a parse error. All sibling tabs already used `{}`, and `Initialize` repopulates the table, so there is no behavioral change.
 
+### Performance
+
+> Measured optimizations being cherry-picked from `phase3-measured-perf` and in-game tested one at a time on top of 1.6.4.
+
+- **[l10n - Literal Translation Cache]** Added a locale-keyed cache for no-argument translation lookups so repeated literal keys resolve without redoing the lookup chain. The cache is reset on locale change and when locale overrides are applied. (Ported from `phase3-measured-perf` 970dd88.)
+
 ## [Unreleased] - Performance Refactor Branches
 
 ### Performance

Localization/l10n.lua

@@ -12,6 +12,7 @@ l10n.npcNameLookup = {}
 l10n.objectNameLookup = {}
 l10n.objectLookup = {}
 l10n.questLookup = {}
+l10n.translationCache = {}
 
 ---@type QuestieDB
 local QuestieDB = QuestieLoader:ImportModule("QuestieDB")
@@ -30,6 +31,10 @@ local supportedLocals = {
     ['koKR'] = true,
 }
 
+local function ResetTranslationCache()
+    l10n.translationCache = {}
+end
+
 function l10n:InitializeLocaleOverride()
     local overridingLocale = QUESTIE_LOCALES_OVERRIDE.locale
     supportedLocals[overridingLocale] = true
@@ -45,6 +50,8 @@ function l10n:InitializeLocaleOverride()
             l10n.translations[id][overridingLocale] = false
         end
     end
+
+    ResetTranslationCache()
 end
 
 ---@param zoneName string
@@ -193,28 +200,42 @@ function _l10n:translate(key, ...)
     key = tostring(key)
     local argCount = select("#", ...)
     if argCount == 0 then
+        local localeCache = l10n.translationCache[locale]
+        if localeCache and localeCache[key] ~= nil then
+            return localeCache[key]
+        end
+        if not localeCache then
+            localeCache = {}
+            l10n.translationCache[locale] = localeCache
+        end
+
         local translationEntry = l10n.translations[key]
         if not translationEntry then
             if (Questie.db.profile.debugEnabled) then Questie:Debug(Questie.DEBUG_ELEVATED, "ERROR: Translations for '" .. tostring(key) .. "' are missing completely!") end
+            localeCache[key] = key
             return key
         end
 
         local translationValue = translationEntry[locale]
         if (not translationValue) then
             if (Questie.db.profile.debugEnabled) then Questie:Debug(Questie.DEBUG_ELEVATED, "ERROR: Translations for '" .. tostring(key) .. "' are missing the entry for language" , locale, "!") end
+            localeCache[key] = key
             return key
         end
 
         if translationValue == true then
             -- Fallback to enUS which is the key
+            localeCache[key] = key
             return key
         end
 
         if type(translationValue) ~= "string" then
             if (Questie.db.profile.debugEnabled) then Questie:Debug(Questie.DEBUG_ELEVATED, "ERROR: Translation for '" .. tostring(key) .. "' is not a string!") end
+            localeCache[key] = key
             return key
         end
 
+        localeCache[key] = translationValue
         return translationValue
     end
 
@@ -283,6 +304,8 @@ function l10n:SetUILocale(lang)
     else
         locale = _l10n:GetFallbackLocale(GetLocale())
     end
+
+    ResetTranslationCache()
 end
 
 function l10n:GetUILocale()

docs/changelog.html

@@ -218,6 +218,11 @@
             <li><strong>[Lua 5.0 &mdash; Modulo Operator]</strong> Routed the nine arithmetic <code>%</code> modulo sites (daily/weekly quest flag tests, Darkmoon Faire cycle math, learner GUID/flag math, race/class flag tests) through the existing <code>math.mod</code> shim. Lua 5.0 has no <code>%</code> operator outside string formatting, so this was a parse error on Vanilla 1.12 clients; the addon now parses on 5.0 through Retail.</li>
             <li><strong>[Lua 5.0 &mdash; Options Tab Tables]</strong> Fixed <code>QuestieOptions.tabs.{auto,dbm,icons,nameplate}</code> being initialized with <code>{...}</code> instead of <code>{}</code>. On Lua 5.1 this silently captured the addon varargs into the table; on Lua 5.0 it is a parse error. All sibling tabs already used <code>{}</code>, and <code>Initialize</code> repopulates the table, so there is no behavioral change.</li>
         </ul>
+        <h3>Performance</h3>
+        <p><em>Measured optimizations being cherry-picked from <code>phase3-measured-perf</code> and in-game tested one at a time on top of 1.6.4.</em></p>
+        <ul>
+            <li><strong>[l10n &mdash; Literal Translation Cache]</strong> Added a locale-keyed cache for no-argument translation lookups so repeated literal keys resolve without redoing the lookup chain. The cache is reset on locale change and when locale overrides are applied. (Ported from <code>phase3-measured-perf</code> 970dd88.)</li>
+        </ul>
         <h3>Bug Fixes</h3>
         <ul>
             <li><strong>[Map &mdash; Suppress Duplicate Native Quest POIs]</strong> Rather than globally disabling the server/Blizzard objective POIs, Questie now keeps them enabled and hides only the individual Blizzard POI buttons for quests that already have a visible Questie POI (per-quest duplicate-POI suppression in <code>QuestieCompat</code>, hooked at init). Blizzard POIs still appear for quests Questie does not cover, but no longer stack on top of Questie's own objective icons.</li>