fix(state): report a failed chat-state write to /set_format

set()/update() logged a failed DB write and returned nothing: the cache already held the new value, so /set_format answered 'Format set' for a change that vanishes on the next restart — a promise the retry queue's enqueue path is already forbidden from making. Both now return whether the write landed, and /set_format's two save paths (set and reset) answer 'in memory only … lost on restart' when it did not. The flag travels as the second tuple element; callers that only relay the value destructure it, callers that ignore it are untouched. A false cannot be forced in a test without a pool-failure seam, so the honest path is pinned by the code, not a fixture.

crates/xmedia-bot/src/handlers/commands.rs

@@ -323,7 +323,7 @@ pub(crate) async fn execute_command(
         }
         Command::RemoveForwardChannel => {
             let chat_id = message.chat.id.0;
-            let text = ctx
+            let (text, _) = ctx
                 .chat_store
                 .update(chat_id, |data| {
                     if data.forward_channel_id.is_some() {
@@ -338,7 +338,7 @@ pub(crate) async fn execute_command(
         }
         Command::EditBeforeForward => {
             let chat_id = message.chat.id.0;
-            let text = ctx
+            let (text, _) = ctx
                 .chat_store
                 .update(chat_id, |data| {
                     if data.forward_channel_id.is_none() {
@@ -393,7 +393,7 @@ pub(crate) async fn execute_command(
                 .await?;
                 return Ok(());
             }
-            let removed = ctx
+            let (removed, _) = ctx
                 .chat_store
                 .update(chat_id, |data| data.template.remove(&name).is_some())
                 .await;
@@ -461,7 +461,8 @@ pub(crate) async fn execute_command(
             // set a format once could never get back to the default (the
             // built-in format string is not something a user can retype).
             if format == "-" {
-                ctx.chat_store
+                let (_, saved) = ctx
+                    .chat_store
                     .update(chat_id, |data| {
                         data.message_format.remove(site);
                     })
@@ -470,7 +471,11 @@ pub(crate) async fn execute_command(
                     ctx.sender,
                     message.chat.id.0,
                     message.id,
-                    "Format reset to the built-in one.",
+                    if saved {
+                        "Format reset to the built-in one.".to_string()
+                    } else {
+                        "Reset in memory only: the database write failed, so it will be lost on restart.".to_string()
+                    },
                 )
                 .await?;
                 return Ok(());
@@ -495,7 +500,8 @@ pub(crate) async fn execute_command(
                 .await?;
                 return Ok(());
             }
-            ctx.chat_store
+            let (_, saved) = ctx
+                .chat_store
                 .update(chat_id, |data| {
                     data.message_format.insert(site.to_string(), format);
                 })
@@ -504,7 +510,11 @@ pub(crate) async fn execute_command(
                 ctx.sender,
                 message.chat.id.0,
                 message.id,
-                "Format set. Use /debug <link> to preview the caption.",
+                if saved {
+                    "Format set. Use /debug <link> to preview the caption.".to_string()
+                } else {
+                    "Set in memory only: the database write failed, so it will be lost on restart. Use /debug <link> to preview the caption.".to_string()
+                },
             )
             .await?;
         }

crates/xmedia-bot/src/state.rs

@@ -105,8 +105,11 @@ impl ChatStore {
         data
     }
 
-    /// Write-through: update the cache and the DB.
+    /// Write-through: update the cache and the DB. Returns whether the DB
-    pub async fn set(&self, chat_id: i64, data: &ChatData) {
+    /// write landed: the cache is updated either way, so `false` means the
+    /// change lives only until the next restart and the caller has to say so
+    /// instead of reporting a save that did not happen.
+    pub async fn set(&self, chat_id: i64, data: &ChatData) -> bool {
         self.cache.lock().insert(chat_id, data.clone());
         let payload = serde_json::to_string(data).expect("chat state serializes");
         let chat_id = chat_id.to_string();
@@ -114,16 +117,16 @@ impl ChatStore {
             .with_conn_or(
                 log::Level::Warn,
                 "chat_state write failed",
-                (),
+                false,
                 move |conn| {
                     conn.execute(
                         "INSERT OR REPLACE INTO chat_state (chat_id, payload) VALUES (?1, ?2)",
                         params![chat_id, payload],
                     )?;
-                    Ok(())
+                    Ok(true)
                 },
             )
-            .await;
+            .await
     }
 
     /// The per-chat async lock serializing get→mutate→set cycles.
@@ -139,14 +142,15 @@ impl ChatStore {
     /// (the batch-forward design spawns several per chat) each snapshot the
     /// same `ChatData` and last-writer-wins would silently drop mutations,
     /// e.g. a second `edit_message` record. The per-chat lock makes the
-    /// cycle atomic. Returns the closure's result.
+    /// cycle atomic. Returns the closure's result plus whether the DB write
-    pub async fn update<R>(&self, chat_id: i64, f: impl FnOnce(&mut ChatData) -> R) -> R {
+    /// landed (see [`Self::set`]); callers that do not care ignore the flag.
+    pub async fn update<R>(&self, chat_id: i64, f: impl FnOnce(&mut ChatData) -> R) -> (R, bool) {
         let lock = self.lock_for(chat_id);
         let _guard = lock.lock().await;
         let mut data = self.get(chat_id).await;
         let r = f(&mut data);
-        self.set(chat_id, &data).await;
+        let saved = self.set(chat_id, &data).await;
-        r
+        (r, saved)
     }
 
     /// Removes edit-before-forward records whose `created_at + ttl` is in the