refactor: reduce console noise about iso deprecation (#3079)

Co-authored-by: Bobbie Goede <[email protected]>

src/utils.ts

@@ -495,6 +495,8 @@ export type LocaleConfig = {
  */
 export const mergeConfigLocales = (configs: LocaleConfig[], baseLocales: LocaleObject[] = []) => {
   const mergedLocales = new Map<string, LocaleObject>()
+  const deprecatedIsolocales = new Set<string>()
+
   for (const locale of baseLocales) {
     mergedLocales.set(locale.code, locale)
   }
@@ -516,9 +518,7 @@ export const mergeConfigLocales = (configs: LocaleConfig[], baseLocales: LocaleO
       delete locale.file
 
       if (locale.iso) {
-        console.warn(
-          `Locale ${locale.iso} uses deprecated \`iso\` property, this will be replaced with \`language\` in v9`
-        )
+        deprecatedIsolocales.add(locale.iso)
         locale.language = locale.iso
         delete locale.iso
       }
@@ -539,6 +539,12 @@ export const mergeConfigLocales = (configs: LocaleConfig[], baseLocales: LocaleO
     }
   }
 
+  if (deprecatedIsolocales.size) {
+    console.warn(
+      `Locales ${[...deprecatedIsolocales].join(', ')} uses deprecated \`iso\` property, this will be replaced with \`language\` in v9`
+    )
+  }
+
   return Array.from(mergedLocales.values())
 }