Try not to mutate

src/state/persisted/util.ts

@@ -4,39 +4,42 @@ import {logger} from '#/logger'
 import {Schema} from '#/state/persisted/schema'
 
 export function normalizeData(data: Schema) {
+  const next = {...data}
+
   /**
    * Normalize language prefs to ensure that these values only contain 2-letter
    * country codes without region.
    */
   try {
-    const next = {...data.languagePrefs}
-    next.primaryLanguage = normalizeLanguageTagToTwoLetterCode(
-      next.primaryLanguage,
+    const langPrefs = {...next.languagePrefs}
+    langPrefs.primaryLanguage = normalizeLanguageTagToTwoLetterCode(
+      langPrefs.primaryLanguage,
     )
-    next.contentLanguages = next.contentLanguages.map(lang =>
+    langPrefs.contentLanguages = langPrefs.contentLanguages.map(lang =>
       normalizeLanguageTagToTwoLetterCode(lang),
     )
-    next.postLanguage = next.postLanguage
+    langPrefs.postLanguage = langPrefs.postLanguage
       .split(',')
       .map(lang => normalizeLanguageTagToTwoLetterCode(lang))
       .filter(Boolean)
       .join(',')
-    next.postLanguageHistory = next.postLanguageHistory.map(postLanguage => {
-      return postLanguage
-        .split(',')
-        .map(lang => normalizeLanguageTagToTwoLetterCode(lang))
-        .filter(Boolean)
-        .join(',')
-    })
-    // mutate last in case anything above fails
-    data.languagePrefs = next
+    langPrefs.postLanguageHistory = langPrefs.postLanguageHistory.map(
+      postLanguage => {
+        return postLanguage
+          .split(',')
+          .map(lang => normalizeLanguageTagToTwoLetterCode(lang))
+          .filter(Boolean)
+          .join(',')
+      },
+    )
+    next.languagePrefs = langPrefs
   } catch (e: any) {
     logger.error(`persisted state: failed to normalize language prefs`, {
       safeMessage: e.message,
     })
   }
 
-  return data
+  return next
 }
 
 export function normalizeLanguageTagToTwoLetterCode(lang: string) {