Synchronize Folder: an absent folder is offline, disks only on request (review fix)

A folder that isn't there (moved whole, or on a disk that isn't
connected) used to scan as "every photo missing", one tick away from
moving a whole disk to Recently Deleted. The scan (on its worker, so an
asleep share never stalls the UI) now reports it as offline and both
commands refuse it; the dialog says so. A whole disk or a folder holding
disks needs `disk: true`, as Remove Disk from Library does; the disk rows
pass it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/engine/src/cmd/library.rs

@@ -1323,7 +1323,7 @@ fn merge_rules(base: &lightcraft_catalog::Filter, patch: &Value, c: &str) -> Res
 /// Whether `path` lies above a disk: some of its `ids` photos are on a disk (not the startup
 /// disk) that the folder does not lie in. Such a folder (`/Volumes`, `/mnt`…) is not a folder of
 /// one disk but a way to reach several.
-fn covers_other_disks(s: &Session, path: &str, ids: &[PhotoId]) -> bool {
+pub(crate) fn covers_other_disks(s: &Session, path: &str, ids: &[PhotoId]) -> bool {
     ids.iter()
         .filter_map(|id| s.catalog.photo(*id))
         .filter_map(|p| lightcraft_catalog::folders::volume_of(p))

crates/engine/src/cmd/sync.rs

@@ -17,12 +17,12 @@ pub fn specs() -> Vec<CommandSpec> {
             "Scan Folder for Changes",
             [],
             None,
-            "{path} — compare a folder of the library (and the folders inside it) with the disk; changes nothing → {path, new: [{path, name, format, …}] files the library doesn't have, duplicates: files whose content it already has, unreadable: [{path, error}], missing: [{id, path}] photos whose file is gone, metadata: [{id, path}] photos whose XMP sidecar was saved after they came in or were last edited here and says something the library doesn't}",
+            "{path, disk?: bool (a whole disk or share, or a folder holding disks)} — compare a folder of the library (and the folders inside it) with the disk; changes nothing → {path, new: [{path, name, format, …}] files the library doesn't have, duplicates: files whose content it already has, unreadable: [{path, error}], missing: [{id, path}] photos whose file is gone, metadata: [{id, path}] photos whose XMP sidecar was saved after they came in or were last edited here and says something the library doesn't}",
             always,
             |s, p| {
                 const C: &str = "folder.scanChanges";
                 let path = path(p, C)?;
-                let changes = scan(s, &path).map_err(|e| bad(C, e.to_string()))?;
+                let changes = scan(s, &path, bool_or(p, "disk", false)).map_err(|e| bad(C, e.to_string()))?;
                 let v = serde_json::to_value(&changes).unwrap_or_default();
                 s.folder_changes = Some(changes);
                 Ok(v)
@@ -33,7 +33,7 @@ pub fn specs() -> Vec<CommandSpec> {
             "Synchronize Folder",
             [],
             None,
-            "{path, importNew?: true, removeMissing?: false, readMetadata?: false} — bring a folder of the library up to date with the disk (see folder.scanChanges): import its new files in place, move photos whose file is gone to Recently Deleted, read XMP sidecars saved by other apps (the sidecar wins); acts on the last folder.scanChanges of the folder while nothing changed in the library since (else scans again); one undo step, no file is touched → {imported, removed, read, failed: [[path, error]]}",
+            "{path, disk?: bool, importNew?: true, removeMissing?: false, readMetadata?: false} — bring a folder of the library up to date with the disk (see folder.scanChanges): import its new files in place, move photos whose file is gone to Recently Deleted, read XMP sidecars saved by other apps (the sidecar wins); acts on the last folder.scanChanges of the folder while nothing changed in the library since (else scans again); one undo step, no file is touched → {imported, removed, read, failed: [[path, error]]}",
             always,
             sync
         ),
@@ -51,7 +51,7 @@ fn sync(s: &mut Session, p: &Value) -> Result<Value> {
     };
     let changes = match s.take_folder_changes(&path) {
         Some(c) => c,
-        None => scan(s, &path).map_err(|e| bad(C, e.to_string()))?,
+        None => scan(s, &path, bool_or(p, "disk", false)).map_err(|e| bad(C, e.to_string()))?,
     };
     let r = synchronize(s, changes, choice)?;
     Ok(json!({"imported": r.imported, "removed": r.removed, "read": r.read, "failed": r.failed}))

crates/engine/src/sync.rs

@@ -65,6 +65,9 @@ pub struct FolderChanges {
     pub missing: Vec<FolderPhoto>,
     /// Photos whose sidecar has news.
     pub metadata: Vec<FolderPhoto>,
+    /// The folder itself is not there (moved or renamed whole, or on a disk that isn't
+    /// connected): nothing else is reported, rather than every photo as missing.
+    pub offline: bool,
     /// The probes of the new files, kept for the import that follows.
     #[serde(skip)]
     probes: HashMap<String, ProbeInfo>,
@@ -110,8 +113,10 @@ fn invalid(msg: impl Into<String>) -> EngineError {
 }
 
 impl SyncInput {
-    /// The scan of folder `path`: a folder the library holds photos in, not the startup disk.
-    pub fn new(s: &mut Session, path: &str) -> Result<SyncInput> {
+    /// The scan of folder `path`: a folder the library holds photos in, not the startup disk. A
+    /// whole disk or share, or a folder that holds disks (`/Volumes`, `/mnt`…), only with `disk`
+    /// (as for Remove Disk from Library: its missing photos can be a whole disk's).
+    pub fn new(s: &mut Session, path: &str, disk: bool) -> Result<SyncInput> {
         let path = path.trim();
         if path.is_empty() {
             return Err(invalid("missing `path`"));
@@ -124,6 +129,9 @@ impl SyncInput {
         if ids.is_empty() {
             return Err(invalid(format!("{path}: no photo in the library was imported from it")));
         }
+        if !disk && (lightcraft_catalog::folders::is_disk_root(path) || crate::cmd::library::covers_other_disks(s, path, &ids)) {
+            return Err(invalid(format!("{path} is a whole disk or holds disks: pass `disk: true` to synchronize it")));
+        }
         let photos = ids.iter().filter_map(|id| s.catalog.photo(*id).map(|p| (Arc::clone(p), s.sidecar_naming(*id)))).collect();
         let (scan, _) = ScanInput::new(s, &[path.to_string()]);
         Ok(SyncInput { folder: path.to_string(), revision: s.catalog.revision, scan, photos, labels: s.catalog.clone() })
@@ -137,6 +145,9 @@ impl SyncInput {
 /// library's photos, which run on several threads too. Stops early when `progress.cancel` is set.
 pub fn scan_with(input: SyncInput, progress: &ScanProgress) -> FolderChanges {
     let SyncInput { folder, revision, scan, photos, labels } = input;
+    if !cfg!(target_arch = "wasm32") && !Path::new(&folder).is_dir() {
+        return FolderChanges { path: folder, revision, offline: true, ..Default::default() };
+    }
     // (no threads on the web: one after the other there)
     #[cfg(target_arch = "wasm32")]
     let (out, checks) = (crate::import::scan_with(scan, std::slice::from_ref(&folder), progress), check_photos(&photos, &labels, progress));
@@ -224,9 +235,17 @@ fn check_photos(photos: &[(Arc<Photo>, SidecarNaming)], labels: &Catalog, progre
 }
 
 /// [`scan_with`] on the calling thread.
-pub fn scan(s: &mut Session, path: &str) -> Result<FolderChanges> {
-    let input = SyncInput::new(s, path)?;
-    Ok(scan_with(input, &ScanProgress::default()))
+pub fn scan(s: &mut Session, path: &str, disk: bool) -> Result<FolderChanges> {
+    let input = SyncInput::new(s, path, disk)?;
+    let changes = scan_with(input, &ScanProgress::default());
+    if changes.offline {
+        return Err(not_there(&changes.path));
+    }
+    Ok(changes)
+}
+
+fn not_there(path: &str) -> EngineError {
+    invalid(format!("{path} is not there (moved, renamed, or on a disk that isn't connected)"))
 }
 
 impl Session {
@@ -265,6 +284,9 @@ fn sidecar_has_news(labels: &Catalog, p: &Photo, naming: SidecarNaming) -> bool
 /// Act on `changes` as `choice` says, as one undo step ("Synchronize Folder"). A missing photo
 /// whose file is back by now is left alone.
 pub fn synchronize(s: &mut Session, changes: FolderChanges, choice: SyncChoice) -> Result<SyncReport> {
+    if changes.offline {
+        return Err(not_there(&changes.path));
+    }
     let mark = s.undo.len();
     let mut report = SyncReport::default();
     let FolderChanges { new, missing, metadata, probes, .. } = changes;

crates/engine/src/tests_sync.rs

@@ -243,7 +243,7 @@ fn a_cancelled_scan_stops_checking_files() {
     let dir = Scratch::new("cancel");
     let mut s = library(&dir);
     std::fs::remove_file(dir.path("trip/day1/b.png")).unwrap();
-    let input = crate::sync::SyncInput::new(&mut s, &dir.path("trip")).unwrap();
+    let input = crate::sync::SyncInput::new(&mut s, &dir.path("trip"), false).unwrap();
     let progress = crate::import::ScanProgress::default();
     progress.cancel.store(true, std::sync::atomic::Ordering::Relaxed);
     let c = crate::sync::scan_with(input, &progress);
@@ -270,3 +270,40 @@ fn many_photos_are_checked_in_parallel_with_the_same_answer() {
     assert_eq!(paths(&r, "missing"), expect_missing);
     assert_eq!(paths(&r, "metadata"), expect_meta);
 }
+
+#[test]
+fn a_folder_that_is_not_there_is_not_scanned_as_if_everything_went_missing() {
+    let dir = Scratch::new("offline");
+    let mut s = library(&dir);
+    // an unplugged disk, or a folder moved away whole
+    std::fs::rename(dir.0.join("trip"), dir.0.join("trip-elsewhere")).unwrap();
+    for cmd in ["folder.scanChanges", "folder.synchronize"] {
+        let e = s.execute(cmd, &json!({"path": dir.path("trip"), "removeMissing": true})).unwrap_err().to_string();
+        assert!(e.contains("not there"), "{cmd}: {e}");
+    }
+    assert_eq!(s.catalog.photos().filter(|p| p.in_library()).count(), 2, "nothing was removed");
+}
+
+#[test]
+fn a_whole_disk_or_a_folder_holding_disks_is_synchronized_only_on_request() {
+    let dir = Scratch::new("disks");
+    let mut s = library(&dir);
+    // a library photo on another disk makes the scratch folder's root look like it holds disks
+    let id = s.catalog.alloc_photo_id();
+    let p = lightcraft_catalog::Photo::new(
+        id,
+        lightcraft_catalog::Source::File { path: "/Volumes/nas/x.jpg".into() },
+        "x.jpg",
+        "JPEG",
+        6,
+        4,
+        "2026-01-01",
+    );
+    s.catalog.apply(lightcraft_catalog::Op::AddPhoto { photo: Box::new(p) }).unwrap();
+    if std::path::Path::new("/Volumes").is_dir() {
+        let e = s.execute("folder.scanChanges", &json!({"path": "/Volumes"})).unwrap_err().to_string();
+        assert!(e.contains("disk: true"), "{e}");
+    }
+    // a folder inside one disk needs nothing more
+    assert!(s.execute("folder.scanChanges", &json!({"path": dir.path("trip")})).is_ok());
+}

crates/ui-egui/locales/de.json

@@ -1903,5 +1903,6 @@
   "Missing photos move to Recently Deleted and can be restored; no file on disk is touched.": "Fehlende Fotos werden nach „Zuletzt gelöscht“ verschoben und können wiederhergestellt werden; keine Datei auf dem Datenträger wird verändert.",
   "Reading a sidecar replaces the photo's rating, labels, metadata and edits with what it says.": "Beim Lesen einer Filialdatei werden Bewertung, Markierungen, Metadaten und Bearbeitungen des Fotos durch ihren Inhalt ersetzt.",
   "Skipped: files already in the library elsewhere": "Übersprungen: Dateien, die bereits an anderer Stelle in der Bibliothek sind",
-  "Skipped: files that can't be read": "Übersprungen: Dateien, die nicht gelesen werden können"
+  "Skipped: files that can't be read": "Übersprungen: Dateien, die nicht gelesen werden können",
+  "This folder isn't there: it was moved or renamed, or its disk isn't connected.": "Dieser Ordner ist nicht vorhanden: Er wurde verschoben oder umbenannt, oder sein Datenträger ist nicht verbunden."
 }

crates/ui-egui/locales/es.json

@@ -1748,5 +1748,6 @@
   "Missing photos move to Recently Deleted and can be restored; no file on disk is touched.": "Las fotos que faltan pasan a Eliminadas recientemente y se pueden restaurar; no se toca ningún archivo del disco.",
   "Reading a sidecar replaces the photo's rating, labels, metadata and edits with what it says.": "Leer un archivo complementario sustituye la valoración, las etiquetas, los metadatos y las ediciones de la foto por lo que contiene.",
   "Skipped: files already in the library elsewhere": "Omitidos: archivos que ya están en la biblioteca en otro lugar",
-  "Skipped: files that can't be read": "Omitidos: archivos que no se pueden leer"
+  "Skipped: files that can't be read": "Omitidos: archivos que no se pueden leer",
+  "This folder isn't there: it was moved or renamed, or its disk isn't connected.": "Esta carpeta no está: se movió o se le cambió el nombre, o su disco no está conectado."
 }

crates/ui-egui/locales/ja.json

@@ -1748,5 +1748,6 @@
   "Missing photos move to Recently Deleted and can be restored; no file on disk is touched.": "見つからない写真は「最近削除した写真」に移動し、復元できます。ディスク上のファイルには手を加えません",
   "Reading a sidecar replaces the photo's rating, labels, metadata and edits with what it says.": "サイドカーを読み込むと、写真のレーティング、ラベル、メタデータ、編集内容がその内容に置き換わります。",
   "Skipped: files already in the library elsewhere": "スキップ: 別の場所ですでにライブラリにあるファイル",
-  "Skipped: files that can't be read": "スキップ: 読み込めないファイル"
+  "Skipped: files that can't be read": "スキップ: 読み込めないファイル",
+  "This folder isn't there: it was moved or renamed, or its disk isn't connected.": "このフォルダが見つかりません。移動または名前の変更がされたか、ディスクが接続されていません。"
 }

crates/ui-egui/locales/pt-br.json

@@ -1748,5 +1748,6 @@
   "Missing photos move to Recently Deleted and can be restored; no file on disk is touched.": "As fotos ausentes vão para Excluídos recentemente e podem ser restauradas; nenhum arquivo no disco é alterado.",
   "Reading a sidecar replaces the photo's rating, labels, metadata and edits with what it says.": "Ler um arquivo auxiliar substitui a classificação, os rótulos, os metadados e as edições da foto pelo que ele contém.",
   "Skipped: files already in the library elsewhere": "Ignorados: arquivos que já estão na biblioteca em outro lugar",
-  "Skipped: files that can't be read": "Ignorados: arquivos que não podem ser lidos"
+  "Skipped: files that can't be read": "Ignorados: arquivos que não podem ser lidos",
+  "This folder isn't there: it was moved or renamed, or its disk isn't connected.": "Esta pasta não está lá: foi movida ou renomeada, ou o disco dela não está conectado."
 }

crates/ui-egui/locales/ru.json

@@ -1421,5 +1421,6 @@
   "Missing photos move to Recently Deleted and can be restored; no file on disk is touched.": "Отсутствующие фото перемещаются в «Недавно удалённые» и могут быть восстановлены; файлы на диске не затрагиваются.",
   "Reading a sidecar replaces the photo's rating, labels, metadata and edits with what it says.": "Чтение файла XMP заменяет рейтинг, метки, метаданные и правки фото его содержимым.",
   "Skipped: files already in the library elsewhere": "Пропущено: файлы, которые уже есть в медиатеке в другом месте",
-  "Skipped: files that can't be read": "Пропущено: файлы, которые не удаётся прочитать"
+  "Skipped: files that can't be read": "Пропущено: файлы, которые не удаётся прочитать",
+  "This folder isn't there: it was moved or renamed, or its disk isn't connected.": "Этой папки нет: её переместили или переименовали, или её диск не подключён."
 }

crates/ui-egui/locales/zh-hans.json

@@ -1748,5 +1748,6 @@
   "Missing photos move to Recently Deleted and can be restored; no file on disk is touched.": "缺失的照片会移到“最近删除”，可以恢复；磁盘上的文件不会被改动。",
   "Reading a sidecar replaces the photo's rating, labels, metadata and edits with what it says.": "读取附属文件会用其内容替换照片的评级、标签、元数据和编辑。",
   "Skipped: files already in the library elsewhere": "已跳过：已在图库其他位置的文件",
-  "Skipped: files that can't be read": "已跳过：无法读取的文件"
+  "Skipped: files that can't be read": "已跳过：无法读取的文件",
+  "This folder isn't there: it was moved or renamed, or its disk isn't connected.": "此文件夹不存在：它已被移动或重命名，或其磁盘未连接。"
 }

crates/ui-egui/locales/zh-hant.json

@@ -1748,5 +1748,6 @@
   "Missing photos move to Recently Deleted and can be restored; no file on disk is touched.": "遺失的照片會移至「最近刪除」，可以還原；磁碟上的檔案不會被更動。",
   "Reading a sidecar replaces the photo's rating, labels, metadata and edits with what it says.": "讀取附屬檔案會以其內容取代照片的評等、標籤、中繼資料和編輯。",
   "Skipped: files already in the library elsewhere": "已略過：已在照片庫其他位置的檔案",
-  "Skipped: files that can't be read": "已略過：無法讀取的檔案"
+  "Skipped: files that can't be read": "已略過：無法讀取的檔案",
+  "This folder isn't there: it was moved or renamed, or its disk isn't connected.": "此資料夾不存在：它已被移動或重新命名，或其磁碟未連接。"
 }

crates/ui-egui/src/panels/left.rs

@@ -1247,7 +1247,8 @@ fn synchronize_item(app: &mut LightcraftApp, ui: &mut egui::Ui, n: &FolderNode,
         .on_hover_text(crate::i18n::tr("Find photos added to or missing from this folder on disk, and XMP sidecars changed by other apps"));
     crate::widgets::register(ui.ctx(), "folderSynchronize", r.rect);
     if r.clicked() {
-        if let Err(e) = crate::sync::open(app, &n.path, name) {
+        // a disk, or a folder holding disks, was chosen as such
+        if let Err(e) = crate::sync::open(app, &n.path, name, n.volume || !n.selectable) {
             app.toast(ui.ctx(), e);
         }
         ui.close();

crates/ui-egui/src/state.rs

@@ -671,6 +671,9 @@ pub enum Dialog {
         path: String,
         /// What the dialog calls it (a folder's last two names).
         name: String,
+        /// A whole disk, or a folder holding disks (`folder.synchronize` `disk`).
+        #[serde(default)]
+        disk: bool,
         /// What the scan found (`None` while it runs).
         counts: Option<SyncCounts>,
         import_new: bool,
@@ -685,6 +688,9 @@ pub enum Dialog {
 #[derive(Clone, Debug, Default, Serialize, Deserialize, PartialEq, Eq)]
 #[serde(rename_all = "camelCase")]
 pub struct SyncCounts {
+    /// The folder isn't there (moved, renamed, or on a disk that isn't connected).
+    #[serde(default)]
+    pub offline: bool,
     pub new: usize,
     pub duplicates: usize,
     pub unreadable: usize,

crates/ui-egui/src/sync.rs

@@ -22,9 +22,9 @@ pub struct SyncTask {
 }
 
 /// Open the dialog for folder `path` (called `name` in it) and start scanning.
-pub fn open(app: &mut LightcraftApp, path: &str, name: &str) -> Result<(), String> {
+pub fn open(app: &mut LightcraftApp, path: &str, name: &str, disk: bool) -> Result<(), String> {
     cancel(app);
-    let input = SyncInput::new(&mut app.session, path).map_err(|e| e.to_string())?;
+    let input = SyncInput::new(&mut app.session, path, disk).map_err(|e| e.to_string())?;
     let progress = Arc::new(ScanProgress::default());
     let (tx, rx) = std::sync::mpsc::channel();
     let p = progress.clone();
@@ -40,6 +40,7 @@ pub fn open(app: &mut LightcraftApp, path: &str, name: &str) -> Result<(), Strin
     app.ui.dialog = Some(Dialog::SynchronizeFolder {
         path: path.to_string(),
         name: name.to_string(),
+        disk,
         counts: None,
         import_new: d.import_new,
         remove_missing: d.remove_missing,
@@ -87,6 +88,7 @@ pub fn poll(app: &mut LightcraftApp, ctx: &egui::Context) {
     };
     app.sync = None;
     let c = SyncCounts {
+        offline: changes.offline,
         new: changes.new.len(),
         duplicates: changes.duplicates,
         unreadable: changes.unreadable.len(),
@@ -106,7 +108,7 @@ fn progress(app: &LightcraftApp) -> Option<(usize, usize)> {
 
 /// The dialog's body.
 pub fn body(app: &LightcraftApp, ui: &mut egui::Ui, dlg: &mut Dialog) {
-    let Dialog::SynchronizeFolder { path, name, counts, import_new, remove_missing, read_metadata } = dlg else { return };
+    let Dialog::SynchronizeFolder { path, name, counts, import_new, remove_missing, read_metadata, .. } = dlg else { return };
     let t = Tokens::get(ui.ctx());
     ui.set_min_width(420.0);
     ui.label(crate::i18n::tr("Bring the library up to date with this folder and the folders inside it:"));
@@ -123,6 +125,10 @@ pub fn body(app: &LightcraftApp, ui: &mut egui::Ui, dlg: &mut Dialog) {
         });
         return;
     };
+    if c.offline {
+        ui.label(crate::i18n::tr("This folder isn't there: it was moved or renamed, or its disk isn't connected."));
+        return;
+    }
     let choice = |ui: &mut egui::Ui, on: &mut bool, n: usize, text: String, widget: &str| {
         let r = ui.add_enabled(n > 0, egui::Checkbox::new(on, text));
         crate::widgets::register(ui.ctx(), widget, r.rect);
@@ -152,11 +158,13 @@ pub fn body(app: &LightcraftApp, ui: &mut egui::Ui, dlg: &mut Dialog) {
 
 /// Synchronize: `folder.synchronize` with the dialog's choices.
 pub fn confirm(app: &mut LightcraftApp, dlg: &Dialog) -> Result<Value, String> {
-    let Dialog::SynchronizeFolder { path, counts: Some(_), import_new, remove_missing, read_metadata, .. } = dlg else {
+    let Dialog::SynchronizeFolder { path, disk, counts: Some(_), import_new, remove_missing, read_metadata, .. } = dlg else {
         return Err("the folder is still being scanned".into());
     };
-    let r =
-        app.run("folder.synchronize", json!({"path": path, "importNew": import_new, "removeMissing": remove_missing, "readMetadata": read_metadata}));
+    let r = app.run(
+        "folder.synchronize",
+        json!({"path": path, "disk": disk, "importNew": import_new, "removeMissing": remove_missing, "readMetadata": read_metadata}),
+    );
     app.session.folder_changes = None;
     r
 }