Autosave: snapshot a new unsaved document before its first edit (#815) (#850)

crates/engine/src/lib.rs

@@ -2890,6 +2890,8 @@ impl Session {
         let id = self.open(name, None, bytes, None)?;
         if let Some(d) = self.docs.iter_mut().find(|d| d.id == id) {
             d.dirty = true;
+            // Unsaved work with no edit yet still needs its first recovery snapshot.
+            d.generation += 1;
         }
         Ok(id)
     }

crates/engine/src/tests.rs

@@ -577,6 +577,19 @@ fn autosave_snapshots_only_changed_documents() {
     assert!(s.autosave_snapshots().is_empty(), "saved documents need no recovery");
 }
 
+#[test]
+fn autosave_snapshots_a_new_unsaved_document_once() {
+    let (mut s, clean) = session_with(1);
+    let id = s.open_new("Untitled.pdf", Arc::new(fixture(1))).unwrap();
+    let snaps = s.autosave_snapshots();
+    assert_eq!(snaps.len(), 1, "the new document is unsaved work");
+    assert_eq!(snaps[0].doc, id);
+    assert!(snaps.iter().all(|x| x.doc != clean), "the clean document stays out");
+    assert!(s.autosave_snapshots().is_empty(), "nothing new since the last snapshot");
+    s.apply(id, Edit::RotatePages { pages: vec![0], degrees: 90 }).unwrap();
+    assert_eq!(s.autosave_snapshots().len(), 1, "a later edit is snapshotted again");
+}
+
 #[test]
 fn recovered_documents_reopen_unsaved_at_their_original_path() {
     let (mut s, id) = session_with(2);