Issue #3406: Auto Import says when it can't read the watched folder

A watched folder that was removed, unmounted or not allowed looked like one with nothing new: the listing error was logged at debug only. It is now logged as a warning once when it starts (and once when the folder can be read again), and Settings > Import shows the reason under the watched folder.

crates/ui-egui/src/app/frame.rs

@@ -91,11 +91,27 @@ impl LightcraftApp {
                 && !self.tasks.is_running(LABEL)
             {
                 self.ui.auto_import_at = now;
-                let work = move || lightcraft_engine::cmd::library::list_auto_import_folder(&folder);
-                let done = |app: &mut LightcraftApp, _ctx: &egui::Context, listing: Result<Vec<(String, u64)>, String>| {
+                let listed = folder.clone();
+                let work = move || lightcraft_engine::cmd::library::list_auto_import_folder(&listed);
+                let done = move |app: &mut LightcraftApp, _ctx: &egui::Context, listing: Result<Vec<(String, u64)>, String>| {
                     let listing = match listing {
-                        Ok(l) => l,
-                        Err(e) => return log::debug!("auto import: {e}"),
+                        Ok(l) => {
+                            if app.ui.auto_import_error.take().is_some() {
+                                log::info!("auto import: the watched folder can be read again: {folder}");
+                            }
+                            l
+                        }
+                        // removed, renamed, unmounted or not allowed: said once, not every few seconds
+                        Err(e) => {
+                            let error = Some((folder, e));
+                            if app.ui.auto_import_error != error {
+                                if let Some((_, e)) = &error {
+                                    log::warn!("auto import: can't read the watched folder {e}");
+                                }
+                                app.ui.auto_import_error = error;
+                            }
+                            return;
+                        }
                     };
                     let p = serde_json::json!({"listing": listing, "start": false});
                     let Ok(r) = app.session.execute("library.autoImportScan", &p) else { return };

crates/ui-egui/src/dialogs/settings/import.rs

@@ -163,6 +163,15 @@ pub(super) fn import_tab(app: &mut LightcraftApp, ui: &mut egui::Ui, t: &Tokens)
                 let _ = app.run("library.autoImport", json!({"folder": null}));
             }
         });
+        // the last listing of the watched folder failed: say why (it reads "OS error: reason")
+        if let (Some(folder), Some((failed, e))) = (&d.auto_folder, &app.ui.auto_import_error)
+            && folder == failed
+        {
+            let reason = e.strip_prefix(folder.as_str()).and_then(|r| r.strip_prefix(": ")).unwrap_or(e);
+            row(ui, t, "", |ui| {
+                ui.label(RichText::new(crate::i18n::tr_format!("Can't read this folder: {}", reason)).size(11.0).color(t.caution));
+            });
+        }
         if d.auto_folder.is_some() {
             row(ui, t, "", |ui| {
                 let mut copy = d.auto_copy;

crates/ui-egui/src/state.rs

@@ -166,6 +166,10 @@ pub struct UiState {
     /// scanning).
     #[serde(skip)]
     pub auto_import_at: f64,
+    /// The watched folder that couldn't be listed and why, as the last listing found it: logged once when it
+    /// starts and once when the folder can be read again, and shown in Settings ▸ Import.
+    #[serde(skip)]
+    pub auto_import_error: Option<(String, String)>,
     /// When the automatic XMP writes that failed were last tried again (monotonic app time), and how
     /// many were waiting then.
     #[serde(skip)]
@@ -421,6 +425,7 @@ impl Default for UiState {
             external_edits: Vec::new(),
             was_focused: true,
             auto_import_at: 0.0,
+            auto_import_error: None,
             sidecar_retry_at: 0.0,
             sidecars_waiting: 0,
             known_cards: None,

crates/ui-egui/src/tests/drop_import.rs

@@ -1107,3 +1107,21 @@ fn public_drop_take_preserves_reentered_barrier_order_and_clears_protection() {
         assert_eq!(photos(&h), 0, "neither taken handles nor refused arrivals replay");
     }
 }
+
+/// A watched folder that can't be listed (removed, unmounted, not allowed) is noted with the reason, for
+/// Settings ▸ Import to show, and the note goes once the folder can be read again.
+#[test]
+fn auto_import_notes_a_watched_folder_it_cannot_read() {
+    let dir = Scratch::new("auto-unreadable");
+    let mut h = app(&dir);
+    let watch = dir.path("watch");
+    h.app.session.import_defaults.auto_folder = Some(watch.clone());
+    assert!(h.step_until(T, |h| h.app.ui.auto_import_error.is_some()), "the missing folder is noted");
+    let (folder, e) = h.app.ui.auto_import_error.clone().unwrap();
+    assert_eq!(folder, watch);
+    assert!(e.starts_with(&watch) && e.len() > watch.len() + 2, "the error says why: {e}");
+    write_png(&dir.path("watch/w.png"), 3);
+    assert!(h.step_until(T, |h| h.app.ui.auto_import_error.is_none()), "readable again: the note goes");
+    assert!(h.step_until(T, |h| photos(h) == 1), "and the photo arrives");
+    h.app.session.import_defaults.auto_folder = None;
+}