Fix divergence bug in undo/redo

Antonio Scandurra created 3 years ago

As part of #1405, we changed the way we performed undo and redo to
support combining transactions that were not temporally adjacent for
IME purposes.

We introduced a bug with that release that caused divergence
when performing undo: the bug was caused by only changing the visibility
of fragments whose insertion id was contained in the undo operation. However,
an undo operation also affects deletions which we were mistakenly not
considering. Randomized tests caught this but I guess we didn't run enough
of them.

Change summary

crates/language/src/proto.rs |  2 --
crates/rpc/proto/zed.proto   |  3 +--
crates/text/src/text.rs      | 12 ++----------
3 files changed, 3 insertions(+), 14 deletions(-)

Detailed changes

crates/language/src/proto.rs

@@ -39,7 +39,6 @@ pub fn serialize_operation(operation: &Operation) -> proto::Operation {
                 local_timestamp: undo.id.value,
                 lamport_timestamp: lamport_timestamp.value,
                 version: serialize_version(&undo.version),
-                transaction_version: serialize_version(&undo.transaction_version),
                 counts: undo
                     .counts
                     .iter()
@@ -199,7 +198,6 @@ pub fn deserialize_operation(message: proto::Operation) -> Result<Operation> {
                             )
                         })
                         .collect(),
-                    transaction_version: deserialize_version(undo.transaction_version),
                 },
             }),
             proto::operation::Variant::UpdateSelections(message) => {

crates/rpc/proto/zed.proto

@@ -901,8 +901,7 @@ message Operation {
         uint32 local_timestamp = 2;
         uint32 lamport_timestamp = 3;
         repeated VectorClockEntry version = 4;
-        repeated VectorClockEntry transaction_version = 6;
-        repeated UndoCount counts = 7;
+        repeated UndoCount counts = 5;
     }
 
     message UpdateSelections {

crates/text/src/text.rs

@@ -512,7 +512,6 @@ pub struct EditOperation {
 pub struct UndoOperation {
     pub id: clock::Local,
     pub counts: HashMap<clock::Local, u32>,
-    pub transaction_version: clock::Global,
     pub version: clock::Global,
 }
 
@@ -1109,14 +1108,8 @@ impl Buffer {
                 let mut fragment = fragment.clone();
                 let fragment_was_visible = fragment.visible;
 
-                if fragment.was_visible(&undo.transaction_version, &self.undo_map)
-                    || undo
-                        .counts
-                        .contains_key(&fragment.insertion_timestamp.local())
-                {
-                    fragment.visible = fragment.is_visible(&self.undo_map);
-                    fragment.max_undos.observe(undo.id);
-                }
+                fragment.visible = fragment.is_visible(&self.undo_map);
+                fragment.max_undos.observe(undo.id);
 
                 let old_start = old_fragments.start().1;
                 let new_start = new_fragments.summary().text.visible;
@@ -1297,7 +1290,6 @@ impl Buffer {
             id: self.local_clock.tick(),
             version: self.version(),
             counts,
-            transaction_version: transaction.start,
         };
         self.apply_undo(&undo)?;
         let operation = Operation::Undo {