Edit > Attach a file: drop the pick if the active document changed while choosing

The picker passed no target, so the staleness guard never ran and a file
chosen after switching tabs was attached to the newly active document. Pass
the active document like Import data and the image picker do. A test covers
the tab switch.

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

crates/ui-egui/src/lib.rs

@@ -1535,7 +1535,8 @@ impl PdfCraftApp {
         #[cfg(not(target_arch = "wasm32"))]
         {
             let dialog = rfd::AsyncFileDialog::new().set_title(tl!("Attach a file").to_string());
-            self.ask_one(pickers::Ask::File(dialog), None, |app, path| app.attach_file(&path));
+            let target = self.active_ids().map(|(_, id)| id);
+            self.ask_one(pickers::Ask::File(dialog), target, |app, path| app.attach_file(&path));
         }
         #[cfg(target_arch = "wasm32")]
         self.notify_tr("Attaching files is not available on the web yet");

crates/ui-egui/tests/attach_picker_target.rs

@@ -0,0 +1,66 @@
+//! Edit ▸ Attach a file… attaches to the document that was active when the picker opened. If the
+//! user switches tabs while choosing, the pick is dropped (and they are told) rather than the file
+//! landing in whichever document is active by then.
+
+use egui_kittest::Harness;
+use pdfcraft_ui_egui::PdfCraftApp;
+
+/// A one-page document with a proper xref table.
+fn fixture() -> Vec<u8> {
+    let objs = [
+        "<< /Type /Catalog /Pages 2 0 R >>".to_string(),
+        "<< /Type /Pages /Kids [3 0 R] /Count 1 /MediaBox [0 0 200 300] >>".to_string(),
+        "<< /Type /Page /Parent 2 0 R >>".to_string(),
+    ];
+    let mut out = b"%PDF-1.7\n".to_vec();
+    let mut offsets = Vec::new();
+    for (i, o) in objs.iter().enumerate() {
+        offsets.push(out.len());
+        out.extend_from_slice(format!("{} 0 obj\n{o}\nendobj\n", i + 1).as_bytes());
+    }
+    let xref = out.len();
+    out.extend_from_slice(format!("xref\n0 {}\n0000000000 65535 f \n", objs.len() + 1).as_bytes());
+    for o in offsets {
+        out.extend_from_slice(format!("{o:010} 00000 n \n").as_bytes());
+    }
+    out.extend_from_slice(format!("trailer\n<< /Size {} /Root 1 0 R >>\nstartxref\n{xref}\n%%EOF\n", objs.len() + 1).as_bytes());
+    out
+}
+
+fn harness() -> Harness<'static, PdfCraftApp> {
+    let mut h = Harness::builder().with_size(egui::vec2(1200.0, 800.0)).build_eframe(|_cc| {
+        let mut app = PdfCraftApp::new();
+        app.set_option("language", "en").unwrap();
+        app.open_bytes("a.pdf", None, fixture()).unwrap();
+        app.open_bytes("b.pdf", None, fixture()).unwrap();
+        app
+    });
+    h.run_steps(2);
+    h
+}
+
+fn dirty(app: &PdfCraftApp, view: usize) -> bool {
+    app.session.get(app.views[view].id).is_some_and(|d| d.dirty)
+}
+
+#[test]
+fn an_attachment_pick_is_dropped_when_the_user_switches_tabs() {
+    let dir = std::env::temp_dir().join(format!("pdfcraft-attach-target-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&dir);
+    std::fs::create_dir_all(&dir).unwrap();
+    let file = dir.join("note.txt");
+    std::fs::write(&file, b"hello").unwrap();
+
+    let mut h = harness();
+    h.state_mut().active = Some(0);
+    h.state_mut().pick_override = Some(vec![file.to_string_lossy().into_owned()]);
+    assert!(h.state_mut().execute("edit.attach"));
+    // The user switches tabs before the pick arrives.
+    h.state_mut().active = Some(1);
+    h.run_steps(2);
+    assert!(!dirty(h.state(), 0), "the document the pick was for is unchanged");
+    assert!(!dirty(h.state(), 1), "the newly active document did not get the attachment");
+    let toast = h.state().toast.as_ref().map(|(m, _)| m.clone()).unwrap_or_default();
+    assert!(toast.contains("document changed"), "the user is told why nothing happened: {toast:?}");
+    let _ = std::fs::remove_dir_all(&dir);
+}