Libraries: let the main library be deleted from a device

Main can go once another library is synced to take over. The server keeps its default library, so this only removes the device's copy, and only Main's own files: its folder is the app data folder. A deleted Main stays deleted across launches, and a device always keeps at least one library, which is now checked before anything is deleted on the server.

README.md

@@ -319,7 +319,9 @@ Deleting a synced library asks whether to **remove it from this device** (it
 stays on the server and on your other devices, and this one stops downloading
 it) or **delete it everywhere**. Other devices keep their copy of a library
 deleted everywhere, marked as deleted from the server, until you remove it or
-put it back. **Main** can be renamed but not deleted.
+put it back. **Main** can be renamed, and deleted from a device once another
+library there is synced; the sync server always keeps it, so it stays on your
+other devices. A device always keeps at least one library.
 
 Libraries' files live in the app-data dir: **Main** where the one library
 always lived, the others under `libraries/`.

src-tauri/src/libraries.rs

@@ -21,8 +21,11 @@ pub struct LibraryInfo {
     pub name: String,
     /// The one that's open.
     pub active: bool,
-    /// The library the device started with, which can't be deleted.
+    /// The library the device started with, which the server won't delete: it
+    /// can only be removed from this device.
     pub is_default: bool,
+    /// Whether it can be deleted from this device right now.
+    pub can_delete: bool,
     /// Whether it should be on the sync server.
     pub sync: bool,
     /// Whether it's linked to a library on the server yet.
@@ -37,6 +40,7 @@ fn info(s: &AppState, lib: &LocalLibrary) -> LibraryInfo {
         name: lib.name.clone(),
         active: s.active_library().id == lib.id,
         is_default: lib.is_default(),
+        can_delete: s.delete_refusal(lib).is_none(),
         sync: lib.sync,
         linked: lib.remote_id.is_some(),
         server_deleted: lib.server_deleted,
@@ -124,13 +128,22 @@ pub async fn rename_library(app: AppHandle, id: String, name: String) -> Result<
 
 /// Delete a library from this device. With `everywhere`, from the sync
 /// server too — and so, at their next sync, from every other device's list
-/// of what's on the server (they keep their own copies until removed).
+/// of what's on the server (they keep their own copies until removed). The
+/// default library stays on the server, which refuses to delete it.
 #[tauri::command]
 pub async fn delete_library(app: AppHandle, id: String, everywhere: bool) -> Result<Vec<LibraryInfo>, String> {
     let libs = blocking(move || {
         let (remote_id, remote) = {
             let s = lock(&app);
             let lib = s.library(&id).ok_or("There's no such library on this device.")?;
+            // Before touching the server, so a refusal here can't leave a
+            // library deleted there and still present on this device.
+            if let Some(refusal) = s.delete_refusal(lib) {
+                return Err(refusal.into());
+            }
+            if everywhere && lib.is_default() {
+                return Err("The main library can't be deleted from the sync server.".into());
+            }
             (lib.remote_id.clone(), account_remote(&s))
         };
         if let (true, Some(rid)) = (everywhere, &remote_id) {

src-tauri/src/state.rs

@@ -29,8 +29,9 @@ struct PersistedConfig {
     /// The sync server this device is (or was last) signed in to.
     #[serde(default)]
     sync: Option<SyncAccount>,
-    /// The libraries on this device, the default one first. Never empty once
-    /// loaded: a config from before named libraries gets the default.
+    /// The libraries on this device, the default one first unless it's been
+    /// deleted. Never empty once loaded: a config from before named libraries
+    /// gets the default.
     #[serde(default)]
     libraries: Vec<LocalLibrary>,
     /// The id of the library that's open.
@@ -117,12 +118,13 @@ fn config_path(data_dir: &Path) -> PathBuf {
 
 fn load_config(data_dir: &Path) -> PersistedConfig {
     let mut cfg = read_config(data_dir);
-    // Before named libraries there was one, which is the default now.
-    if !cfg.libraries.iter().any(LocalLibrary::is_default) {
-        cfg.libraries.insert(0, default_library());
+    // Before named libraries there was one, which is the default now. A list
+    // without it is different: the user deleted it.
+    if cfg.libraries.is_empty() {
+        cfg.libraries.push(default_library());
     }
     if !cfg.libraries.iter().any(|l| l.id == cfg.active_library) {
-        cfg.active_library = DEFAULT_LIBRARY.into();
+        cfg.active_library = cfg.libraries[0].id.clone();
     }
     cfg
 }
@@ -400,24 +402,59 @@ impl AppState {
         self.reopen_catalog()
     }
 
+    /// Why `lib` can't be deleted from this device, if it can't. A device
+    /// always keeps a library, and the default one goes only when a synced one
+    /// can take over from it.
+    pub fn delete_refusal(&self, lib: &LocalLibrary) -> Option<&'static str> {
+        let mut others = self.config.libraries.iter().filter(|l| l.id != lib.id);
+        if lib.is_default() && !others.clone().any(|l| l.remote_id.is_some()) {
+            return Some("The main library can only be deleted once another library is synced.");
+        }
+        others.next().is_none().then_some("This is the only library on this device.")
+    }
+
     /// Delete a library and its files from this device. The active one is
-    /// left by switching to the default first; the default itself stays.
+    /// left by switching to another first: a synced one when that's what let
+    /// the default library go.
     pub fn delete_library(&mut self, id: &str) -> Result<LocalLibrary, String> {
         let lib = self.library(id).cloned().ok_or("There's no such library on this device.")?;
-        if lib.is_default() {
-            return Err("The main library can't be deleted.".into());
+        if let Some(refusal) = self.delete_refusal(&lib) {
+            return Err(refusal.into());
         }
         if self.sync_running {
             return Err("Wait for the sync to finish, then try again.".into());
         }
         if self.config.active_library == id {
-            self.switch_library(DEFAULT_LIBRARY)?;
+            let next = self
+                .config
+                .libraries
+                .iter()
+                .find(|l| l.id != id && (!lib.is_default() || l.remote_id.is_some()))
+                .map(|l| l.id.clone())
+                .ok_or("There's no other library to open.")?;
+            self.switch_library(&next)?;
         }
         self.config.libraries.retain(|l| l.id != id);
         save_config(&self.data_dir, &self.config);
-        let dir = self.library_dir(id);
-        if let Err(e) = std::fs::remove_dir_all(&dir) {
-            crate::mlog!("delete_library: couldn't remove {}: {e}", dir.display());
+        if lib.is_default() {
+            // Only the default library could ask this, and it's gone.
+            self.sync_needs_choice = false;
+            // Its folder is the data folder itself, holding the app's own
+            // files and the other libraries, so only its files go.
+            let working = self.working_path(id);
+            for path in [working.with_extension("db-journal"), working, self.base_path(id)] {
+                match std::fs::remove_file(&path) {
+                    Err(e) if e.kind() != std::io::ErrorKind::NotFound => {
+                        crate::mlog!("delete_library: couldn't remove {}: {e}", path.display());
+                    }
+                    _ => {}
+                }
+            }
+        } else {
+            let dir = self.library_dir(id);
+            if let Err(e) = std::fs::remove_dir_all(&dir) {
+                crate::mlog!("delete_library: couldn't remove {}: {e}", dir.display());
+            }
         }
         Ok(lib)
     }
@@ -715,11 +752,87 @@ mod tests {
         assert!(s.delete_library(&lib.id).is_err(), "not mid-sync");
         s.sync_running = false;
 
-        assert!(s.delete_library(DEFAULT_LIBRARY).is_err());
+        assert!(s.delete_library(DEFAULT_LIBRARY).is_err(), "nothing synced to take over");
         s.delete_library(&lib.id).unwrap();
         assert_eq!(s.active_library().id, DEFAULT_LIBRARY, "deleting the open one switches away");
         assert!(!s.library_dir(&lib.id).exists());
         assert_eq!(s.libraries().len(), 1);
         std::fs::remove_dir_all(&dir).unwrap();
     }
+
+    #[test]
+    fn the_default_library_goes_only_when_a_synced_one_can_take_over() {
+        let dir = scratch("delete-default");
+        let mut s = AppState::new(dir.clone());
+        let unsynced = s.create_library("Scratch", false, None).unwrap();
+        let waiting = s.create_library("Trades", true, None).unwrap();
+        assert!(s.delete_library(DEFAULT_LIBRARY).is_err(), "not on the server yet");
+        assert_eq!(s.libraries().len(), 3);
+
+        let linked = s.create_library("Cube", true, Some("r1".into())).unwrap();
+        std::fs::write(dir.join("sync-server-base.json"), "{}").unwrap();
+        reference_with(&dir.join("reference.db"), "Card");
+        s.sync_needs_choice = true;
+        s.delete_library(DEFAULT_LIBRARY).unwrap();
+
+        assert_eq!(s.active_library().id, linked.id, "the synced one takes over");
+        assert_eq!(s.working_db_path, s.working_path(&linked.id));
+        assert!(s.library(DEFAULT_LIBRARY).is_none());
+        assert!(!s.sync_needs_choice);
+        assert!(!dir.join("working.db").exists());
+        assert!(!dir.join("sync-server-base.json").exists());
+        // Everything around it in the data folder survives.
+        assert!(dir.join("reference.db").exists());
+        assert!(config_path(&dir).exists());
+        assert!(s.working_path(&linked.id).exists());
+        assert!(s.working_path(&unsynced.id).exists());
+        assert!(s.working_path(&waiting.id).exists());
+
+        // It stays gone, and the libraries left can still be opened.
+        let mut s = AppState::new(dir.clone());
+        assert_eq!(s.active_library().id, linked.id);
+        assert!(s.library(DEFAULT_LIBRARY).is_none());
+        s.switch_library(&unsynced.id).unwrap();
+        std::fs::remove_dir_all(&dir).unwrap();
+    }
+
+    #[test]
+    fn the_last_library_on_a_device_stays() {
+        let dir = scratch("delete-last");
+        let mut s = AppState::new(dir.clone());
+        let lib = s.create_library("Cube", true, Some("r1".into())).unwrap();
+        let other = s.create_library("Trades", false, None).unwrap();
+        s.delete_library(DEFAULT_LIBRARY).unwrap();
+
+        s.delete_library(&lib.id).unwrap();
+        assert_eq!(s.active_library().id, other.id, "with no default to fall back on");
+
+        assert!(s.delete_library(&other.id).is_err());
+        assert_eq!(s.libraries().len(), 1);
+        assert!(s.working_path(&other.id).exists());
+        std::fs::remove_dir_all(&dir).unwrap();
+    }
+
+    #[test]
+    fn a_config_without_the_default_library_keeps_it_deleted() {
+        let dir = scratch("default-gone");
+        let lib = LocalLibrary {
+            id: "abc".into(),
+            name: "Cube".into(),
+            remote_id: Some("r1".into()),
+            sync: true,
+            server_deleted: false,
+        };
+        let cfg = PersistedConfig {
+            libraries: vec![lib.clone()],
+            active_library: DEFAULT_LIBRARY.into(),
+            ..Default::default()
+        };
+        save_config(&dir, &cfg);
+
+        let back = load_config(&dir);
+        assert_eq!(back.libraries, vec![lib]);
+        assert_eq!(back.active_library, "abc", "an active library that's gone falls to one that's here");
+        std::fs::remove_dir_all(&dir).unwrap();
+    }
 }

src-tauri/src/sync.rs

@@ -762,7 +762,8 @@ impl LibraryPlan {
 ///
 /// - a linked library whose server library is gone is flagged as deleted
 ///   there, and keeps its contents;
-/// - the default library links to the account's default;
+/// - the default library links to the account's default, which is never
+///   downloaded: this device has either kept it off the server or deleted it;
 /// - a server library not on this device links to a not-yet-linked library
 ///   here with the same name, or is downloaded — unless it was removed from
 ///   this device;
@@ -1100,6 +1101,16 @@ mod tests {
         assert_eq!(plan, LibraryPlan::default());
     }
 
+    #[test]
+    fn a_default_library_deleted_here_isnt_downloaded_back() {
+        let plan = plan_libraries(
+            &[local("abc", "Cube", Some("c"))],
+            &[],
+            &[server("m", "Main", true), server("c", "Cube", false)],
+        );
+        assert_eq!(plan, LibraryPlan::default());
+    }
+
     #[test]
     fn libraries_started_elsewhere_are_downloaded_unless_removed_here() {
         let libs = [local("default", "Main", Some("m"))];

src/Libraries.tsx

@@ -87,6 +87,8 @@ function DeleteLibraryDialog({
 }) {
   const [error, setError] = useState<string | null>(null);
   const [busy, setBusy] = useState(false);
+  // The server keeps the main library, so this device can only let go of it.
+  const offerEverywhere = lib.linked && !lib.is_default;
 
   async function remove(everywhere: boolean) {
     setBusy(true);
@@ -101,12 +103,17 @@ function DeleteLibraryDialog({
 
   return (
     <DialogFrame title={`Delete ${lib.name}?`} onCancel={onCancel}>
-      {lib.linked ? (
+      {offerEverywhere ? (
         <p>
           <strong>Remove from this device</strong> keeps it on the sync server for your other
           devices; this one stops downloading it. <strong>Delete everywhere</strong> also removes
           it from the server, and your other devices keep only the copy they already have.
         </p>
+      ) : lib.linked ? (
+        <p>
+          This device's copy will be deleted and it stops syncing here. It stays on the sync server
+          for your other devices, since the main library can't be deleted from there.
+        </p>
       ) : (
         <p>Its cards and decks will be deleted from this device. This can't be undone.</p>
       )}
@@ -115,13 +122,13 @@ function DeleteLibraryDialog({
         <button onClick={onCancel} disabled={busy}>
           Cancel
         </button>
-        {lib.linked && (
+        {offerEverywhere && (
           <button onClick={() => remove(false)} disabled={busy}>
             Remove from this device
           </button>
         )}
-        <button className="danger" onClick={() => remove(lib.linked)} disabled={busy}>
-          {lib.linked ? "Delete everywhere" : "Delete"}
+        <button className="danger" onClick={() => remove(offerEverywhere)} disabled={busy}>
+          {offerEverywhere ? "Delete everywhere" : lib.linked ? "Remove from this device" : "Delete"}
         </button>
       </div>
     </DialogFrame>
@@ -337,7 +344,7 @@ export function LibrariesPanel({
                 }}
                 disabled={busy}
               />
-              {!lib.is_default && (
+              {lib.can_delete && (
                 <IconButton
                   icon={Icons.trash}
                   label={`Delete ${lib.name}`}

src/api.ts

@@ -351,6 +351,7 @@ export interface LibraryInfo {
   active: boolean;
   /** The library the device started with, which can't be deleted. */
   is_default: boolean;
+  can_delete: boolean;
   /** Whether it should be on the sync server. */
   sync: boolean;
   /** Whether it's linked to a library on the server yet. */