Merge pull request #3444 from vitorpamplona/claude/bottom-nav-reset-defaults-jxg5z0

Persist bottom bar defaults as blank sentinel for auto-migration

amethyst/src/main/java/com/vitorpamplona/amethyst/model/preferences/UISharedPreferences.kt

@@ -205,7 +205,7 @@ class UiSharedPreferences(
                     preferences[UI_PROPOSE_AI_IMPROVEMENTS] = sharedSettings.automaticallyProposeAiImprovements.name
                     preferences[UI_USE_TRACKED_BROADCASTS] = sharedSettings.useTrackedBroadcasts.name
                     preferences[UI_AUTOMATICALLY_CREATE_DRAFTS] = sharedSettings.automaticallyCreateDrafts.name
-                    preferences[UI_BOTTOM_BAR_ITEMS] = JsonMapper.toJson(sharedSettings.bottomBarItems)
+                    preferences[UI_BOTTOM_BAR_ITEMS] = encodeBottomBarItems(sharedSettings.bottomBarItems)
                     preferences[UI_SHOW_HOME_NEW_THREADS_TAB] = sharedSettings.showHomeNewThreadsTab
                     preferences[UI_SHOW_HOME_CONVERSATIONS_TAB] = sharedSettings.showHomeConversationsTab
                     preferences[UI_SHOW_HOME_EVERYTHING_TAB] = sharedSettings.showHomeEverythingTab
@@ -226,7 +226,19 @@ class UiSharedPreferences(
             }
         }
 
-        private fun decodeBottomBarItems(raw: String): List<BottomBarEntry>? {
+        /**
+         * Persists "follow the defaults" as a blank sentinel instead of the concrete default list.
+         *
+         * A user who resets the bottom bar (or who never customized it) should track whatever
+         * [DefaultBottomBarEntries] is in the *installed* app version. Storing the concrete list would
+         * pin them to today's default, so a future version that changes the default would never reach
+         * them. Storing a blank value instead makes [decodeBottomBarItems] resolve it back to the
+         * current [DefaultBottomBarEntries] on every load — i.e. the user is automatically migrated to
+         * the new default. Any genuinely customized bar is still stored as JSON.
+         */
+        internal fun encodeBottomBarItems(items: List<BottomBarEntry>): String = if (items == DefaultBottomBarEntries) "" else JsonMapper.toJson(items)
+
+        internal fun decodeBottomBarItems(raw: String): List<BottomBarEntry>? {
             if (raw.isBlank()) return DefaultBottomBarEntries
             // Current format: a JSON list of BottomBarEntry (built-ins + favorites).
             runCatching { return JsonMapper.fromJson<List<BottomBarEntry>>(raw) }

amethyst/src/test/java/com/vitorpamplona/amethyst/model/preferences/BottomBarPersistenceTest.kt

@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.model.preferences
+
+import com.vitorpamplona.amethyst.ui.navigation.bottombars.BottomBarEntry
+import com.vitorpamplona.amethyst.ui.navigation.bottombars.DefaultBottomBarEntries
+import com.vitorpamplona.amethyst.ui.navigation.bottombars.NavBarItem
+import org.junit.Assert.assertEquals
+import org.junit.Test
+
+/**
+ * Locks the "reset to defaults migrates automatically" behavior.
+ *
+ * Resetting the bottom bar (or never customizing it) is persisted as a blank sentinel rather than the
+ * concrete default list, so that a user on the defaults tracks whatever [DefaultBottomBarEntries] the
+ * *installed* app version ships. If a future version changes the default, that blank value resolves to
+ * the new default on load — the user is migrated instead of being pinned to the old default.
+ */
+class BottomBarPersistenceTest {
+    @Test
+    fun defaultsAreStoredAsBlankSentinel() {
+        assertEquals("", UiSharedPreferences.encodeBottomBarItems(DefaultBottomBarEntries))
+    }
+
+    @Test
+    fun blankSentinelDecodesToCurrentDefaults() {
+        // The blank sentinel resolves to whatever DefaultBottomBarEntries this build ships. Because it
+        // returns the current constant (not a value frozen at reset time), a future version that changes
+        // the default automatically migrates every user who is on the defaults.
+        assertEquals(DefaultBottomBarEntries, UiSharedPreferences.decodeBottomBarItems(""))
+    }
+
+    @Test
+    fun customizedBarIsStoredVerbatimAndRoundTrips() {
+        val custom =
+            listOf(
+                BottomBarEntry.BuiltIn(NavBarItem.HOME),
+                BottomBarEntry.Favorite("url:https://example.com"),
+            )
+        val encoded = UiSharedPreferences.encodeBottomBarItems(custom)
+        assertEquals(custom, UiSharedPreferences.decodeBottomBarItems(encoded))
+    }
+}