From f35c419f432ea85f657b5ffaf5d536e04ddc029c Mon Sep 17 00:00:00 2001
From: Nathan Sobo <nathan@zed.dev>
Date: Fri, 10 Dec 2021 18:08:26 -0700
Subject: [PATCH] Return optional transaction ids from undo/redo

This will allow the editor to restore selections that it associated with the start or end of a transaction.
---
 crates/editor/src/multi_buffer.rs |  4 ++--
 crates/language/src/buffer.rs     | 28 ++++++++++++++++++----------
 crates/text/src/text.rs           | 18 ++++++++++++------
 3 files changed, 32 insertions(+), 18 deletions(-)

diff --git a/crates/editor/src/multi_buffer.rs b/crates/editor/src/multi_buffer.rs
index cc1425f1cf7d4aa7bdc5f3a6ffa48ddb78fb4e5a..8163a7bd23554aae8a35843d374820c71130411f 100644
--- a/crates/editor/src/multi_buffer.rs
+++ b/crates/editor/src/multi_buffer.rs
@@ -224,14 +224,14 @@ impl MultiBuffer {
         })
     }
 
-    pub fn undo(&mut self, cx: &mut ModelContext<Self>) {
+    pub fn undo(&mut self, cx: &mut ModelContext<Self>) -> Option<TransactionId> {
         // TODO
         self.as_singleton()
             .unwrap()
             .update(cx, |buffer, cx| buffer.undo(cx))
     }
 
-    pub fn redo(&mut self, cx: &mut ModelContext<Self>) {
+    pub fn redo(&mut self, cx: &mut ModelContext<Self>) -> Option<TransactionId> {
         // TODO
         self.as_singleton()
             .unwrap()
diff --git a/crates/language/src/buffer.rs b/crates/language/src/buffer.rs
index ddeb5328cbb430a7f28e9623e60dfa85ba0f674d..1830e49bf76d7a96a1822a748bcf15e939a7d8cf 100644
--- a/crates/language/src/buffer.rs
+++ b/crates/language/src/buffer.rs
@@ -1443,26 +1443,34 @@ impl Buffer {
         cx.notify();
     }
 
-    pub fn undo(&mut self, cx: &mut ModelContext<Self>) {
+    pub fn undo(&mut self, cx: &mut ModelContext<Self>) -> Option<TransactionId> {
         let was_dirty = self.is_dirty();
         let old_version = self.version.clone();
 
-        for operation in self.text.undo() {
-            self.send_operation(Operation::Buffer(operation), cx);
+        if let Some((transaction_id, operations)) = self.text.undo() {
+            for operation in operations {
+                self.send_operation(Operation::Buffer(operation), cx);
+            }
+            self.did_edit(&old_version, was_dirty, cx);
+            Some(transaction_id)
+        } else {
+            None
         }
-
-        self.did_edit(&old_version, was_dirty, cx);
     }
 
-    pub fn redo(&mut self, cx: &mut ModelContext<Self>) {
+    pub fn redo(&mut self, cx: &mut ModelContext<Self>) -> Option<TransactionId> {
         let was_dirty = self.is_dirty();
         let old_version = self.version.clone();
 
-        for operation in self.text.redo() {
-            self.send_operation(Operation::Buffer(operation), cx);
+        if let Some((transaction_id, operations)) = self.text.redo() {
+            for operation in operations {
+                self.send_operation(Operation::Buffer(operation), cx);
+            }
+            self.did_edit(&old_version, was_dirty, cx);
+            Some(transaction_id)
+        } else {
+            None
         }
-
-        self.did_edit(&old_version, was_dirty, cx);
     }
 }
 
diff --git a/crates/text/src/text.rs b/crates/text/src/text.rs
index a8eb32888f39c0abf1f185613d7f30dd88bbd6f7..525cbc43662a03af9eadec7b5ea868a6d3c8a1e4 100644
--- a/crates/text/src/text.rs
+++ b/crates/text/src/text.rs
@@ -1221,28 +1221,34 @@ impl Buffer {
         self.history.ops.values()
     }
 
-    pub fn undo(&mut self) -> Vec<Operation> {
-        let mut ops = Vec::new();
+    pub fn undo(&mut self) -> Option<(TransactionId, Vec<Operation>)> {
         if let Some(transaction) = self.history.pop_undo().cloned() {
+            let transaction_id = transaction.id;
             let selections = transaction.selections_before.clone();
+            let mut ops = Vec::new();
             ops.push(self.undo_or_redo(transaction).unwrap());
             for (set_id, selections) in selections {
                 ops.extend(self.restore_selection_set(set_id, selections));
             }
+            Some((transaction_id, ops))
+        } else {
+            None
         }
-        ops
     }
 
-    pub fn redo(&mut self) -> Vec<Operation> {
-        let mut ops = Vec::new();
+    pub fn redo(&mut self) -> Option<(TransactionId, Vec<Operation>)> {
         if let Some(transaction) = self.history.pop_redo().cloned() {
+            let transaction_id = transaction.id;
             let selections = transaction.selections_after.clone();
+            let mut ops = Vec::new();
             ops.push(self.undo_or_redo(transaction).unwrap());
             for (set_id, selections) in selections {
                 ops.extend(self.restore_selection_set(set_id, selections));
             }
+            Some((transaction_id, ops))
+        } else {
+            None
         }
-        ops
     }
 
     fn undo_or_redo(&mut self, transaction: Transaction) -> Result<Operation> {