fix(undo): ignore revived tree metadata in remote diffs

crates/loro-internal/src/undo.rs

@@ -402,13 +402,32 @@ impl Stack {
     }
 
     pub fn compose_remote_event(&mut self, diff: &[&ContainerDiff]) {
+        self.compose_remote_event_excluding(diff, &FxHashSet::default());
+    }
+
+    pub fn compose_remote_event_excluding(
+        &mut self,
+        diff: &[&ContainerDiff],
+        exclude: &FxHashSet<ContainerID>,
+    ) {
         if self.is_empty() {
             return;
         }
 
         let remote_diff = &mut self.stack.back_mut().unwrap().1;
         let mut remote_diff = remote_diff.lock();
         for e in diff {
+            if exclude.contains(&e.id) {
+                continue;
+            }
+            // Skip containers whose path passes through an excluded container: they
+            // are part of the same bring-back subtree emitted by the diff calculator.
+            if e.path
+                .iter()
+                .any(|(ancestor, _)| exclude.contains(ancestor))
+            {
+                continue;
+            }
             if let Some(d) = remote_diff.cid_to_events.get_mut(&e.id) {
                 d.compose_ref(&e.diff);
             } else {
@@ -616,8 +635,30 @@ impl UndoManager {
                 let lock = inner_clone.lock();
                 let mut inner = lock.borrow_mut();
 
+                // When the diff calculator checks out from the LCA forward to the
+                // import frontier, a tree node that is alive on both sides can appear
+                // as Delete then Create in the same external TreeDiff (e.g. due to
+                // concurrent sibling insertions changing node ordering). In that case
+                // TreeDiffCalculator marks the node's associated_meta_container as a
+                // new container and emits full-state bring-back diffs for the entire
+                // metadata subtree. Those diffs look like concurrent insertions to the
+                // undo transform but carry no real new content.
+                //
+                // Note: same-target Delete+Create can also represent genuine
+                // delete-then-resurrect sequences. The exclusion below applies only to
+                // the metadata subtree's *bring-back* content; real edits to those
+                // containers within the same import batch are an edge case that could
+                // still be over-excluded. This heuristic is correct for the common case
+                // (issue #915) where no concurrent edits touch the subtree.
+                let mut revived_meta_containers: FxHashSet<ContainerID> = FxHashSet::default();
                 for e in event.events {
                     if let Diff::Tree(tree) = &e.diff {
+                        let mut deleted: FxHashSet<loro_common::TreeID> = FxHashSet::default();
+                        for item in &tree.diff {
+                            if let TreeExternalDiff::Delete { .. } = &item.action {
+                                deleted.insert(item.target);
+                            }
+                        }
                         for item in &tree.diff {
                             let target = item.target;
                             if let TreeExternalDiff::Create { .. } = &item.action {
@@ -626,15 +667,28 @@ impl UndoManager {
                                 remap_containers_clone
                                     .lock()
                                     .remove(&target.associated_meta_container());
+
+                                if deleted.contains(&target) {
+                                    // Same-target Delete+Create in one diff: the diff
+                                    // calculator emitted full-state bring-back diffs for
+                                    // this node's metadata subtree. Exclude those from
+                                    // remote_diff so they don't corrupt undo transforms.
+                                    revived_meta_containers
+                                        .insert(target.associated_meta_container());
+                                }
                             }
                         }
                     }
                 }
 
                 let is_import_disjoint = inner.is_disjoint_with_group(event.events);
 
-                inner.undo_stack.compose_remote_event(event.events);
-                inner.redo_stack.compose_remote_event(event.events);
+                inner
+                    .undo_stack
+                    .compose_remote_event_excluding(event.events, &revived_meta_containers);
+                inner
+                    .redo_stack
+                    .compose_remote_event_excluding(event.events, &revived_meta_containers);
 
                 // If the import is not disjoint, we end the active group
                 // all subsequent changes will be new undo items

crates/loro/tests/issue.rs

@@ -2,7 +2,7 @@
 #![allow(unexpected_cfgs)]
 use loro::{
     cursor::Cursor, ContainerID, ContainerTrait, EncodedBlobMode, ExportMode, LoroDoc, LoroError,
-    LoroList, LoroText, UndoManager,
+    LoroList, LoroMap, LoroText, UndoManager,
 };
 use std::sync::{Arc, Mutex};
 use tracing::{trace, trace_span};
@@ -468,3 +468,197 @@ fn get_unknown_cursor_position_but_its_in_pending() {
     assert!(!doc_1.has_container(&text.id()));
     assert_eq!(doc_1.get_path_to_container(&text.id()), None);
 }
+
+#[test]
+fn test_undo_nested_text_in_tree_after_independent_import_issue_915() {
+    // undo() returned false for a text edit inside a tree node's meta map after
+    // importing from a completely independent document (issue #915).
+    let doc_a = LoroDoc::new();
+    doc_a.set_peer_id(1).unwrap();
+
+    let tree = doc_a.get_tree("tree");
+    let node = tree.create(None).unwrap();
+    let meta = tree.get_meta(node).unwrap();
+    let text = meta.insert_container("content", LoroText::new()).unwrap();
+    text.insert(0, "Hello").unwrap();
+    doc_a.commit();
+
+    // UndoManager created after initial content (matches the reported condition)
+    let mut undo = UndoManager::new(&doc_a);
+    undo.set_merge_interval(0);
+
+    text.insert(5, " world").unwrap();
+    doc_a.commit();
+    assert_eq!(text.to_string(), "Hello world");
+    assert!(undo.can_undo());
+
+    // Import from a completely independent doc (no shared history)
+    let doc_b = LoroDoc::new();
+    doc_b.set_peer_id(2).unwrap();
+    let tree_b = doc_b.get_tree("tree");
+    let node_b = tree_b.create(None).unwrap();
+    tree_b
+        .get_meta(node_b)
+        .unwrap()
+        .insert_container("content", LoroText::new())
+        .unwrap()
+        .insert(0, "From B")
+        .unwrap();
+    doc_b.commit();
+
+    doc_a
+        .import(&doc_b.export(ExportMode::all_updates()).unwrap())
+        .unwrap();
+
+    assert!(undo.can_undo());
+    assert!(undo.undo().unwrap());
+    assert_eq!(text.to_string(), "Hello");
+}
+
+#[test]
+fn test_undo_deeply_nested_text_in_tree_after_independent_import_issue_915() {
+    // Deeper nesting: tree node meta -> child map -> LoroText
+    let doc_a = LoroDoc::new();
+    doc_a.set_peer_id(1).unwrap();
+
+    let tree = doc_a.get_tree("tree");
+    let node = tree.create(None).unwrap();
+    let child_map = tree
+        .get_meta(node)
+        .unwrap()
+        .insert_container("data", LoroMap::new())
+        .unwrap();
+    let text = child_map
+        .insert_container("content", LoroText::new())
+        .unwrap();
+    text.insert(0, "Hello").unwrap();
+    doc_a.commit();
+
+    let mut undo = UndoManager::new(&doc_a);
+    undo.set_merge_interval(0);
+
+    text.insert(5, " world").unwrap();
+    doc_a.commit();
+
+    let doc_b = LoroDoc::new();
+    doc_b.set_peer_id(2).unwrap();
+    let node_b = doc_b.get_tree("tree").create(None).unwrap();
+    doc_b
+        .get_tree("tree")
+        .get_meta(node_b)
+        .unwrap()
+        .insert("kind", "paragraph")
+        .unwrap();
+    doc_b.commit();
+
+    doc_a
+        .import(&doc_b.export(ExportMode::all_updates()).unwrap())
+        .unwrap();
+
+    assert!(undo.can_undo());
+    assert!(undo.undo().unwrap());
+    assert_eq!(text.to_string(), "Hello");
+}
+
+#[test]
+fn test_undo_multi_node_reindex_after_independent_import_issue_915() {
+    // Multiple local tree nodes reindexed by a single independent import
+    let doc_a = LoroDoc::new();
+    doc_a.set_peer_id(1).unwrap();
+
+    let tree = doc_a.get_tree("tree");
+    let node1 = tree.create(None).unwrap();
+    let node2 = tree.create(None).unwrap();
+    let text1 = tree
+        .get_meta(node1)
+        .unwrap()
+        .insert_container("t", LoroText::new())
+        .unwrap();
+    let text2 = tree
+        .get_meta(node2)
+        .unwrap()
+        .insert_container("t", LoroText::new())
+        .unwrap();
+    text1.insert(0, "A").unwrap();
+    text2.insert(0, "B").unwrap();
+    doc_a.commit();
+
+    let mut undo = UndoManager::new(&doc_a);
+    undo.set_merge_interval(0);
+
+    text1.insert(1, "1").unwrap();
+    text2.insert(1, "2").unwrap();
+    doc_a.commit();
+    assert_eq!(text1.to_string(), "A1");
+    assert_eq!(text2.to_string(), "B2");
+
+    // Independent doc adds two root nodes, forcing reindex of both peer-1 nodes
+    let doc_b = LoroDoc::new();
+    doc_b.set_peer_id(2).unwrap();
+    doc_b.get_tree("tree").create(None).unwrap();
+    doc_b.get_tree("tree").create(None).unwrap();
+    doc_b.commit();
+
+    doc_a
+        .import(&doc_b.export(ExportMode::all_updates()).unwrap())
+        .unwrap();
+
+    assert!(undo.can_undo());
+    assert!(undo.undo().unwrap());
+    assert_eq!(text1.to_string(), "A");
+    assert_eq!(text2.to_string(), "B");
+}
+
+#[test]
+fn test_undo_preserves_real_remote_edit_on_revived_node_issue_915() {
+    // Risk case: same-event Delete+Create on a node whose text was also concurrently
+    // edited by the remote peer. The real remote edit must survive the undo transform.
+    //
+    // doc_a: node with "Hello", undo target = append " world"
+    // doc_b: (1) adds its own root node (triggers node reindex in merge diff)
+    //        (2) concurrently prepends "Hi " to the same text
+    // After undo: text should be "Hi Hello" — remote prepend stays, local append removed.
+    let doc_a = LoroDoc::new();
+    doc_a.set_peer_id(1).unwrap();
+
+    let tree = doc_a.get_tree("tree");
+    let node = tree.create(None).unwrap();
+    let text = tree
+        .get_meta(node)
+        .unwrap()
+        .insert_container("content", LoroText::new())
+        .unwrap();
+    text.insert(0, "Hello").unwrap();
+    doc_a.commit();
+
+    let mut undo = UndoManager::new(&doc_a);
+    undo.set_merge_interval(0);
+
+    text.insert(5, " world").unwrap();
+    doc_a.commit();
+    assert_eq!(text.to_string(), "Hello world");
+
+    // doc_b starts from doc_a's state, then diverges
+    let doc_b = LoroDoc::new();
+    doc_b.set_peer_id(2).unwrap();
+    doc_b
+        .import(&doc_a.export(ExportMode::all_updates()).unwrap())
+        .unwrap();
+
+    doc_b.get_tree("tree").create(None).unwrap();
+    let text_b: LoroText = match doc_b.get_container(text.id().clone()).unwrap() {
+        loro::Container::Text(t) => t,
+        _ => panic!("expected text"),
+    };
+    text_b.insert(0, "Hi ").unwrap();
+    doc_b.commit();
+
+    doc_a
+        .import(&doc_b.export(ExportMode::all_updates()).unwrap())
+        .unwrap();
+    assert_eq!(text.to_string(), "Hi Hello world");
+
+    assert!(undo.can_undo());
+    assert!(undo.undo().unwrap());
+    assert_eq!(text.to_string(), "Hi Hello");
+}