Merge pull request #272 from zed-industries/fold-map-edits

Antonio Scandurra created

Don't rely on `Buffer::edits_since` to keep `FoldMap` up-to-date

Change summary

Cargo.lock                                 |   3 
crates/editor/src/display_map.rs           |  34 
crates/editor/src/display_map/block_map.rs |  32 
crates/editor/src/display_map/fold_map.rs  | 663 +++++++++++------------
crates/editor/src/display_map/tab_map.rs   |   7 
crates/editor/src/display_map/wrap_map.rs  |  47 
crates/editor/src/editor.rs                |   2 
crates/language/src/buffer.rs              |  61 +-
crates/project/src/worktree.rs             |   5 
crates/text/Cargo.toml                     |   3 
crates/text/src/patch.rs                   |  81 +-
crates/text/src/tests.rs                   |  36 +
crates/text/src/text.rs                    | 146 ++++
13 files changed, 646 insertions(+), 474 deletions(-)

Detailed changes

Cargo.lock 🔗

@@ -4849,8 +4849,11 @@ dependencies = [
  "arrayvec 0.7.1",
  "clock",
  "collections",
+ "ctor",
+ "env_logger",
  "gpui",
  "log",
+ "parking_lot",
  "rand 0.8.3",
  "smallvec",
  "sum_tree",

crates/editor/src/display_map.rs 🔗

@@ -1,6 +1,5 @@
 mod block_map;
 mod fold_map;
-mod patch;
 mod tab_map;
 mod wrap_map;
 
@@ -11,7 +10,7 @@ use gpui::{
     fonts::{FontId, HighlightStyle},
     AppContext, Entity, ModelContext, ModelHandle,
 };
-use language::{Anchor, Buffer, Point, ToOffset, ToPoint};
+use language::{Anchor, Buffer, Point, Subscription as BufferSubscription, ToOffset, ToPoint};
 use std::{
     collections::{HashMap, HashSet},
     ops::Range,
@@ -28,6 +27,7 @@ pub trait ToDisplayPoint {
 
 pub struct DisplayMap {
     buffer: ModelHandle<Buffer>,
+    buffer_subscription: BufferSubscription,
     fold_map: FoldMap,
     tab_map: TabMap,
     wrap_map: ModelHandle<WrapMap>,
@@ -47,13 +47,15 @@ impl DisplayMap {
         wrap_width: Option<f32>,
         cx: &mut ModelContext<Self>,
     ) -> Self {
-        let (fold_map, snapshot) = FoldMap::new(buffer.clone(), cx);
+        let buffer_subscription = buffer.update(cx, |buffer, _| buffer.subscribe());
+        let (fold_map, snapshot) = FoldMap::new(buffer.read(cx).snapshot());
         let (tab_map, snapshot) = TabMap::new(snapshot, tab_size);
         let (wrap_map, snapshot) = WrapMap::new(snapshot, font_id, font_size, wrap_width, cx);
         let block_map = BlockMap::new(buffer.clone(), snapshot);
         cx.observe(&wrap_map, |_, _, cx| cx.notify()).detach();
         DisplayMap {
             buffer,
+            buffer_subscription,
             fold_map,
             tab_map,
             wrap_map,
@@ -62,7 +64,9 @@ impl DisplayMap {
     }
 
     pub fn snapshot(&self, cx: &mut ModelContext<Self>) -> DisplayMapSnapshot {
-        let (folds_snapshot, edits) = self.fold_map.read(cx);
+        let buffer_snapshot = self.buffer.read(cx).snapshot();
+        let edits = self.buffer_subscription.consume().into_inner();
+        let (folds_snapshot, edits) = self.fold_map.read(buffer_snapshot, edits);
         let (tabs_snapshot, edits) = self.tab_map.sync(folds_snapshot.clone(), edits);
         let (wraps_snapshot, edits) = self
             .wrap_map
@@ -83,13 +87,15 @@ impl DisplayMap {
         ranges: impl IntoIterator<Item = Range<T>>,
         cx: &mut ModelContext<Self>,
     ) {
-        let (mut fold_map, snapshot, edits) = self.fold_map.write(cx);
+        let snapshot = self.buffer.read(cx).snapshot();
+        let edits = self.buffer_subscription.consume().into_inner();
+        let (mut fold_map, snapshot, edits) = self.fold_map.write(snapshot, edits);
         let (snapshot, edits) = self.tab_map.sync(snapshot, edits);
         let (snapshot, edits) = self
             .wrap_map
             .update(cx, |map, cx| map.sync(snapshot, edits, cx));
         self.block_map.read(snapshot, edits, cx);
-        let (snapshot, edits) = fold_map.fold(ranges, cx);
+        let (snapshot, edits) = fold_map.fold(ranges);
         let (snapshot, edits) = self.tab_map.sync(snapshot, edits);
         let (snapshot, edits) = self
             .wrap_map
@@ -102,13 +108,15 @@ impl DisplayMap {
         ranges: impl IntoIterator<Item = Range<T>>,
         cx: &mut ModelContext<Self>,
     ) {
-        let (mut fold_map, snapshot, edits) = self.fold_map.write(cx);
+        let snapshot = self.buffer.read(cx).snapshot();
+        let edits = self.buffer_subscription.consume().into_inner();
+        let (mut fold_map, snapshot, edits) = self.fold_map.write(snapshot, edits);
         let (snapshot, edits) = self.tab_map.sync(snapshot, edits);
         let (snapshot, edits) = self
             .wrap_map
             .update(cx, |map, cx| map.sync(snapshot, edits, cx));
         self.block_map.read(snapshot, edits, cx);
-        let (snapshot, edits) = fold_map.unfold(ranges, cx);
+        let (snapshot, edits) = fold_map.unfold(ranges);
         let (snapshot, edits) = self.tab_map.sync(snapshot, edits);
         let (snapshot, edits) = self
             .wrap_map
@@ -125,7 +133,9 @@ impl DisplayMap {
         P: ToOffset + Clone,
         T: Into<Rope> + Clone,
     {
-        let (snapshot, edits) = self.fold_map.read(cx);
+        let snapshot = self.buffer.read(cx).snapshot();
+        let edits = self.buffer_subscription.consume().into_inner();
+        let (snapshot, edits) = self.fold_map.read(snapshot, edits);
         let (snapshot, edits) = self.tab_map.sync(snapshot, edits);
         let (snapshot, edits) = self
             .wrap_map
@@ -143,7 +153,9 @@ impl DisplayMap {
     }
 
     pub fn remove_blocks(&mut self, ids: HashSet<BlockId>, cx: &mut ModelContext<Self>) {
-        let (snapshot, edits) = self.fold_map.read(cx);
+        let snapshot = self.buffer.read(cx).snapshot();
+        let edits = self.buffer_subscription.consume().into_inner();
+        let (snapshot, edits) = self.fold_map.read(snapshot, edits);
         let (snapshot, edits) = self.tab_map.sync(snapshot, edits);
         let (snapshot, edits) = self
             .wrap_map
@@ -525,7 +537,7 @@ mod tests {
                     }
                 }
                 _ => {
-                    buffer.update(&mut cx, |buffer, _| buffer.randomly_edit(&mut rng, 5));
+                    buffer.update(&mut cx, |buffer, cx| buffer.randomly_edit(&mut rng, 5, cx));
                 }
             }
 

crates/editor/src/display_map/block_map.rs 🔗

@@ -1104,7 +1104,7 @@ mod tests {
         let text = "aaa\nbbb\nccc\nddd";
 
         let buffer = cx.add_model(|cx| Buffer::new(0, text, cx));
-        let (fold_map, folds_snapshot) = FoldMap::new(buffer.clone(), cx);
+        let (fold_map, folds_snapshot) = FoldMap::new(buffer.read(cx).snapshot());
         let (tab_map, tabs_snapshot) = TabMap::new(folds_snapshot.clone(), 1);
         let (wrap_map, wraps_snapshot) = WrapMap::new(tabs_snapshot, font_id, 14.0, None, cx);
         let mut block_map = BlockMap::new(buffer.clone(), wraps_snapshot.clone());
@@ -1228,11 +1228,13 @@ mod tests {
 
         // Insert a line break, separating two block decorations into separate
         // lines.
-        buffer.update(cx, |buffer, cx| {
-            buffer.edit([Point::new(1, 1)..Point::new(1, 1)], "!!!\n", cx)
+        let (buffer_snapshot, buffer_edits) = buffer.update(cx, |buffer, cx| {
+            let v0 = buffer.version();
+            buffer.edit([Point::new(1, 1)..Point::new(1, 1)], "!!!\n", cx);
+            (buffer.snapshot(), buffer.edits_since(&v0).collect())
         });
 
-        let (folds_snapshot, fold_edits) = fold_map.read(cx);
+        let (folds_snapshot, fold_edits) = fold_map.read(buffer_snapshot, buffer_edits);
         let (tabs_snapshot, tab_edits) = tab_map.sync(folds_snapshot, fold_edits);
         let (wraps_snapshot, wrap_edits) = wrap_map.update(cx, |wrap_map, cx| {
             wrap_map.sync(tabs_snapshot, tab_edits, cx)
@@ -1255,7 +1257,7 @@ mod tests {
         let text = "one two three\nfour five six\nseven eight";
 
         let buffer = cx.add_model(|cx| Buffer::new(0, text, cx));
-        let (_, folds_snapshot) = FoldMap::new(buffer.clone(), cx);
+        let (_, folds_snapshot) = FoldMap::new(buffer.read(cx).snapshot());
         let (_, tabs_snapshot) = TabMap::new(folds_snapshot.clone(), 1);
         let (_, wraps_snapshot) = WrapMap::new(tabs_snapshot, font_id, 14.0, Some(60.), cx);
         let mut block_map = BlockMap::new(buffer.clone(), wraps_snapshot.clone());
@@ -1317,7 +1319,8 @@ mod tests {
             log::info!("initial buffer text: {:?}", text);
             Buffer::new(0, text, cx)
         });
-        let (fold_map, folds_snapshot) = FoldMap::new(buffer.clone(), cx);
+        let mut buffer_snapshot = buffer.read(cx).snapshot();
+        let (fold_map, folds_snapshot) = FoldMap::new(buffer_snapshot.clone());
         let (tab_map, tabs_snapshot) = TabMap::new(folds_snapshot.clone(), tab_size);
         let (wrap_map, wraps_snapshot) =
             WrapMap::new(tabs_snapshot, font_id, font_size, wrap_width, cx);
@@ -1325,6 +1328,7 @@ mod tests {
         let mut expected_blocks = Vec::new();
 
         for _ in 0..operations {
+            let mut buffer_edits = Vec::new();
             match rng.gen_range(0..=100) {
                 0..=19 => {
                     let wrap_width = if rng.gen_bool(0.2) {
@@ -1375,7 +1379,8 @@ mod tests {
                         })
                         .collect::<Vec<_>>();
 
-                    let (folds_snapshot, fold_edits) = fold_map.read(cx);
+                    let (folds_snapshot, fold_edits) =
+                        fold_map.read(buffer_snapshot.clone(), vec![]);
                     let (tabs_snapshot, tab_edits) = tab_map.sync(folds_snapshot, fold_edits);
                     let (wraps_snapshot, wrap_edits) = wrap_map.update(cx, |wrap_map, cx| {
                         wrap_map.sync(tabs_snapshot, tab_edits, cx)
@@ -1396,7 +1401,8 @@ mod tests {
                         })
                         .collect();
 
-                    let (folds_snapshot, fold_edits) = fold_map.read(cx);
+                    let (folds_snapshot, fold_edits) =
+                        fold_map.read(buffer_snapshot.clone(), vec![]);
                     let (tabs_snapshot, tab_edits) = tab_map.sync(folds_snapshot, fold_edits);
                     let (wraps_snapshot, wrap_edits) = wrap_map.update(cx, |wrap_map, cx| {
                         wrap_map.sync(tabs_snapshot, tab_edits, cx)
@@ -1405,14 +1411,18 @@ mod tests {
                     block_map.remove(block_ids_to_remove, cx);
                 }
                 _ => {
-                    buffer.update(cx, |buffer, _| {
-                        buffer.randomly_edit(&mut rng, 1);
+                    buffer.update(cx, |buffer, cx| {
+                        let v0 = buffer.version();
+                        let edit_count = rng.gen_range(1..=5);
+                        buffer.randomly_edit(&mut rng, edit_count, cx);
                         log::info!("buffer text: {:?}", buffer.text());
+                        buffer_edits.extend(buffer.edits_since(&v0));
+                        buffer_snapshot = buffer.snapshot();
                     });
                 }
             }
 
-            let (folds_snapshot, fold_edits) = fold_map.read(cx);
+            let (folds_snapshot, fold_edits) = fold_map.read(buffer_snapshot.clone(), buffer_edits);
             let (tabs_snapshot, tab_edits) = tab_map.sync(folds_snapshot, fold_edits);
             let (wraps_snapshot, wrap_edits) = wrap_map.update(cx, |wrap_map, cx| {
                 wrap_map.sync(tabs_snapshot, tab_edits, cx)

crates/editor/src/display_map/fold_map.rs 🔗

@@ -1,9 +1,11 @@
-use gpui::{AppContext, ModelHandle};
-use language::{Anchor, AnchorRangeExt, Buffer, Chunk, Point, PointUtf16, TextSummary, ToOffset};
+use language::{
+    Anchor, AnchorRangeExt, Chunk, Edit, Point, PointUtf16, Snapshot as BufferSnapshot,
+    TextSummary, ToOffset,
+};
 use parking_lot::Mutex;
 use std::{
     cmp::{self, Ordering},
-    iter, mem,
+    iter,
     ops::Range,
     sync::atomic::{AtomicUsize, Ordering::SeqCst},
 };
@@ -100,11 +102,10 @@ impl<'a> FoldMapWriter<'a> {
     pub fn fold<T: ToOffset>(
         &mut self,
         ranges: impl IntoIterator<Item = Range<T>>,
-        cx: &AppContext,
     ) -> (Snapshot, Vec<FoldEdit>) {
         let mut edits = Vec::new();
         let mut folds = Vec::new();
-        let buffer = self.0.buffer.read(cx).snapshot();
+        let buffer = self.0.buffer.lock().clone();
         for range in ranges.into_iter() {
             let range = range.start.to_offset(&buffer)..range.end.to_offset(&buffer);
             if range.start != range.end {
@@ -131,11 +132,11 @@ impl<'a> FoldMapWriter<'a> {
         };
 
         consolidate_buffer_edits(&mut edits);
-        let edits = self.0.apply_edits(edits, cx);
+        let edits = self.0.sync(buffer.clone(), edits);
         let snapshot = Snapshot {
             transforms: self.0.transforms.lock().clone(),
             folds: self.0.folds.clone(),
-            buffer_snapshot: self.0.buffer.read(cx).snapshot(),
+            buffer_snapshot: buffer,
             version: self.0.version.load(SeqCst),
         };
         (snapshot, edits)
@@ -144,13 +145,12 @@ impl<'a> FoldMapWriter<'a> {
     pub fn unfold<T: ToOffset>(
         &mut self,
         ranges: impl IntoIterator<Item = Range<T>>,
-        cx: &AppContext,
     ) -> (Snapshot, Vec<FoldEdit>) {
         let mut edits = Vec::new();
         let mut fold_ixs_to_delete = Vec::new();
-        let buffer = self.0.buffer.read(cx).snapshot();
+        let buffer = self.0.buffer.lock().clone();
         for range in ranges.into_iter() {
-            // Remove intersecting folds and add their ranges to edits that are passed to apply_edits.
+            // Remove intersecting folds and add their ranges to edits that are passed to sync.
             let mut folds_cursor = intersecting_folds(&buffer, &self.0.folds, range, true);
             while let Some(fold) = folds_cursor.item() {
                 let offset_range = fold.0.start.to_offset(&buffer)..fold.0.end.to_offset(&buffer);
@@ -178,11 +178,11 @@ impl<'a> FoldMapWriter<'a> {
         };
 
         consolidate_buffer_edits(&mut edits);
-        let edits = self.0.apply_edits(edits, cx);
+        let edits = self.0.sync(buffer.clone(), edits);
         let snapshot = Snapshot {
             transforms: self.0.transforms.lock().clone(),
             folds: self.0.folds.clone(),
-            buffer_snapshot: self.0.buffer.read(cx).snapshot(),
+            buffer_snapshot: buffer,
             version: self.0.version.load(SeqCst),
         };
         (snapshot, edits)
@@ -190,25 +190,16 @@ impl<'a> FoldMapWriter<'a> {
 }
 
 pub struct FoldMap {
-    buffer: ModelHandle<Buffer>,
+    buffer: Mutex<BufferSnapshot>,
     transforms: Mutex<SumTree<Transform>>,
     folds: SumTree<Fold>,
-    last_sync: Mutex<SyncState>,
     version: AtomicUsize,
 }
 
-#[derive(Clone)]
-struct SyncState {
-    version: clock::Global,
-    parse_count: usize,
-    diagnostics_update_count: usize,
-}
-
 impl FoldMap {
-    pub fn new(buffer_handle: ModelHandle<Buffer>, cx: &AppContext) -> (Self, Snapshot) {
-        let buffer = buffer_handle.read(cx);
+    pub fn new(buffer: BufferSnapshot) -> (Self, Snapshot) {
         let this = Self {
-            buffer: buffer_handle,
+            buffer: Mutex::new(buffer.clone()),
             folds: Default::default(),
             transforms: Mutex::new(SumTree::from_item(
                 Transform {
@@ -220,147 +211,185 @@ impl FoldMap {
                 },
                 &(),
             )),
-            last_sync: Mutex::new(SyncState {
-                version: buffer.version(),
-                parse_count: buffer.parse_count(),
-                diagnostics_update_count: buffer.diagnostics_update_count(),
-            }),
-            version: AtomicUsize::new(0),
+            version: Default::default(),
+        };
+
+        let snapshot = Snapshot {
+            transforms: this.transforms.lock().clone(),
+            folds: this.folds.clone(),
+            buffer_snapshot: this.buffer.lock().clone(),
+            version: this.version.load(SeqCst),
         };
-        let (snapshot, _) = this.read(cx);
         (this, snapshot)
     }
 
-    pub fn read(&self, cx: &AppContext) -> (Snapshot, Vec<FoldEdit>) {
-        let edits = self.sync(cx);
-        self.check_invariants(cx);
+    pub fn read(
+        &self,
+        buffer: BufferSnapshot,
+        edits: Vec<Edit<usize>>,
+    ) -> (Snapshot, Vec<FoldEdit>) {
+        let edits = self.sync(buffer, edits);
+        self.check_invariants();
         let snapshot = Snapshot {
             transforms: self.transforms.lock().clone(),
             folds: self.folds.clone(),
-            buffer_snapshot: self.buffer.read(cx).snapshot(),
+            buffer_snapshot: self.buffer.lock().clone(),
             version: self.version.load(SeqCst),
         };
         (snapshot, edits)
     }
 
-    pub fn write(&mut self, cx: &AppContext) -> (FoldMapWriter, Snapshot, Vec<FoldEdit>) {
-        let (snapshot, edits) = self.read(cx);
+    pub fn write(
+        &mut self,
+        buffer: BufferSnapshot,
+        edits: Vec<Edit<usize>>,
+    ) -> (FoldMapWriter, Snapshot, Vec<FoldEdit>) {
+        let (snapshot, edits) = self.read(buffer, edits);
         (FoldMapWriter(self), snapshot, edits)
     }
 
-    fn sync(&self, cx: &AppContext) -> Vec<FoldEdit> {
-        let buffer = self.buffer.read(cx);
-        let last_sync = mem::replace(
-            &mut *self.last_sync.lock(),
-            SyncState {
-                version: buffer.version(),
-                parse_count: buffer.parse_count(),
-                diagnostics_update_count: buffer.diagnostics_update_count(),
-            },
-        );
-        let edits = buffer
-            .edits_since(&last_sync.version)
-            .map(Into::into)
-            .collect::<Vec<_>>();
-        if edits.is_empty() {
-            if last_sync.parse_count != buffer.parse_count()
-                || last_sync.diagnostics_update_count != buffer.diagnostics_update_count()
-            {
-                self.version.fetch_add(1, SeqCst);
-            }
-            Vec::new()
-        } else {
-            self.apply_edits(edits, cx)
-        }
-    }
-
-    fn check_invariants(&self, cx: &AppContext) {
+    fn check_invariants(&self) {
         if cfg!(test) {
-            let buffer = self.buffer.read(cx);
             assert_eq!(
                 self.transforms.lock().summary().input.bytes,
-                buffer.len(),
+                self.buffer.lock().len(),
                 "transform tree does not match buffer's length"
             );
         }
     }
 
-    fn apply_edits(&self, buffer_edits: Vec<text::Edit<usize>>, cx: &AppContext) -> Vec<FoldEdit> {
-        let buffer = self.buffer.read(cx).snapshot();
-        let mut buffer_edits_iter = buffer_edits.iter().cloned().peekable();
+    fn sync(
+        &self,
+        new_buffer: BufferSnapshot,
+        buffer_edits: Vec<text::Edit<usize>>,
+    ) -> Vec<FoldEdit> {
+        if buffer_edits.is_empty() {
+            let mut buffer = self.buffer.lock();
+            if buffer.parse_count() != new_buffer.parse_count()
+                || buffer.diagnostics_update_count() != new_buffer.diagnostics_update_count()
+            {
+                self.version.fetch_add(1, SeqCst);
+            }
+            *buffer = new_buffer;
+            Vec::new()
+        } else {
+            let mut buffer_edits_iter = buffer_edits.iter().cloned().peekable();
 
-        let mut new_transforms = SumTree::new();
-        let mut transforms = self.transforms.lock();
-        let mut cursor = transforms.cursor::<usize>();
-        cursor.seek(&0, Bias::Right, &());
+            let mut new_transforms = SumTree::new();
+            let mut transforms = self.transforms.lock();
+            let mut cursor = transforms.cursor::<usize>();
+            cursor.seek(&0, Bias::Right, &());
 
-        while let Some(mut edit) = buffer_edits_iter.next() {
-            new_transforms.push_tree(cursor.slice(&edit.old.start, Bias::Left, &()), &());
-            edit.new.start -= edit.old.start - cursor.start();
-            edit.old.start = *cursor.start();
+            while let Some(mut edit) = buffer_edits_iter.next() {
+                new_transforms.push_tree(cursor.slice(&edit.old.start, Bias::Left, &()), &());
+                edit.new.start -= edit.old.start - cursor.start();
+                edit.old.start = *cursor.start();
 
-            cursor.seek(&edit.old.end, Bias::Right, &());
-            cursor.next(&());
+                cursor.seek(&edit.old.end, Bias::Right, &());
+                cursor.next(&());
 
-            let mut delta = edit.new.len() as isize - edit.old.len() as isize;
-            loop {
-                edit.old.end = *cursor.start();
+                let mut delta = edit.new.len() as isize - edit.old.len() as isize;
+                loop {
+                    edit.old.end = *cursor.start();
 
-                if let Some(next_edit) = buffer_edits_iter.peek() {
-                    if next_edit.old.start > edit.old.end {
-                        break;
-                    }
+                    if let Some(next_edit) = buffer_edits_iter.peek() {
+                        if next_edit.old.start > edit.old.end {
+                            break;
+                        }
 
-                    let next_edit = buffer_edits_iter.next().unwrap();
-                    delta += next_edit.new.len() as isize - next_edit.old.len() as isize;
+                        let next_edit = buffer_edits_iter.next().unwrap();
+                        delta += next_edit.new.len() as isize - next_edit.old.len() as isize;
 
-                    if next_edit.old.end >= edit.old.end {
-                        edit.old.end = next_edit.old.end;
-                        cursor.seek(&edit.old.end, Bias::Right, &());
-                        cursor.next(&());
+                        if next_edit.old.end >= edit.old.end {
+                            edit.old.end = next_edit.old.end;
+                            cursor.seek(&edit.old.end, Bias::Right, &());
+                            cursor.next(&());
+                        }
+                    } else {
+                        break;
                     }
-                } else {
-                    break;
                 }
-            }
 
-            edit.new.end = ((edit.new.start + edit.old.len()) as isize + delta) as usize;
+                edit.new.end = ((edit.new.start + edit.old.len()) as isize + delta) as usize;
 
-            let anchor = buffer.anchor_before(edit.new.start);
-            let mut folds_cursor = self.folds.cursor::<Fold>();
-            folds_cursor.seek(&Fold(anchor..Anchor::max()), Bias::Left, &buffer);
+                let anchor = new_buffer.anchor_before(edit.new.start);
+                let mut folds_cursor = self.folds.cursor::<Fold>();
+                folds_cursor.seek(&Fold(anchor..Anchor::max()), Bias::Left, &new_buffer);
 
-            let mut folds = iter::from_fn({
-                let buffer = &buffer;
-                move || {
-                    let item = folds_cursor
-                        .item()
-                        .map(|f| f.0.start.to_offset(buffer)..f.0.end.to_offset(buffer));
-                    folds_cursor.next(buffer);
-                    item
-                }
-            })
-            .peekable();
+                let mut folds = iter::from_fn({
+                    let buffer = &new_buffer;
+                    move || {
+                        let item = folds_cursor
+                            .item()
+                            .map(|f| f.0.start.to_offset(buffer)..f.0.end.to_offset(buffer));
+                        folds_cursor.next(buffer);
+                        item
+                    }
+                })
+                .peekable();
 
-            while folds.peek().map_or(false, |fold| fold.start < edit.new.end) {
-                let mut fold = folds.next().unwrap();
-                let sum = new_transforms.summary();
+                while folds.peek().map_or(false, |fold| fold.start < edit.new.end) {
+                    let mut fold = folds.next().unwrap();
+                    let sum = new_transforms.summary();
+
+                    assert!(fold.start >= sum.input.bytes);
+
+                    while folds
+                        .peek()
+                        .map_or(false, |next_fold| next_fold.start <= fold.end)
+                    {
+                        let next_fold = folds.next().unwrap();
+                        if next_fold.end > fold.end {
+                            fold.end = next_fold.end;
+                        }
+                    }
 
-                assert!(fold.start >= sum.input.bytes);
+                    if fold.start > sum.input.bytes {
+                        let text_summary = new_buffer
+                            .text_summary_for_range::<TextSummary, _>(sum.input.bytes..fold.start);
+                        new_transforms.push(
+                            Transform {
+                                summary: TransformSummary {
+                                    output: text_summary.clone(),
+                                    input: text_summary,
+                                },
+                                output_text: None,
+                            },
+                            &(),
+                        );
+                    }
 
-                while folds
-                    .peek()
-                    .map_or(false, |next_fold| next_fold.start <= fold.end)
-                {
-                    let next_fold = folds.next().unwrap();
-                    if next_fold.end > fold.end {
-                        fold.end = next_fold.end;
+                    if fold.end > fold.start {
+                        let output_text = "…";
+                        let chars = output_text.chars().count() as u32;
+                        let lines = Point::new(0, output_text.len() as u32);
+                        let lines_utf16 =
+                            PointUtf16::new(0, output_text.encode_utf16().count() as u32);
+                        new_transforms.push(
+                            Transform {
+                                summary: TransformSummary {
+                                    output: TextSummary {
+                                        bytes: output_text.len(),
+                                        lines,
+                                        lines_utf16,
+                                        first_line_chars: chars,
+                                        last_line_chars: chars,
+                                        longest_row: 0,
+                                        longest_row_chars: chars,
+                                    },
+                                    input: new_buffer.text_summary_for_range(fold.start..fold.end),
+                                },
+                                output_text: Some(output_text),
+                            },
+                            &(),
+                        );
                     }
                 }
 
-                if fold.start > sum.input.bytes {
-                    let text_summary = buffer
-                        .text_summary_for_range::<TextSummary, _>(sum.input.bytes..fold.start);
+                let sum = new_transforms.summary();
+                if sum.input.bytes < edit.new.end {
+                    let text_summary = new_buffer
+                        .text_summary_for_range::<TextSummary, _>(sum.input.bytes..edit.new.end);
                     new_transforms.push(
                         Transform {
                             summary: TransformSummary {
@@ -372,37 +401,11 @@ impl FoldMap {
                         &(),
                     );
                 }
-
-                if fold.end > fold.start {
-                    let output_text = "…";
-                    let chars = output_text.chars().count() as u32;
-                    let lines = Point::new(0, output_text.len() as u32);
-                    let lines_utf16 = PointUtf16::new(0, output_text.encode_utf16().count() as u32);
-                    new_transforms.push(
-                        Transform {
-                            summary: TransformSummary {
-                                output: TextSummary {
-                                    bytes: output_text.len(),
-                                    lines,
-                                    lines_utf16,
-                                    first_line_chars: chars,
-                                    last_line_chars: chars,
-                                    longest_row: 0,
-                                    longest_row_chars: chars,
-                                },
-                                input: buffer.text_summary_for_range(fold.start..fold.end),
-                            },
-                            output_text: Some(output_text),
-                        },
-                        &(),
-                    );
-                }
             }
 
-            let sum = new_transforms.summary();
-            if sum.input.bytes < edit.new.end {
-                let text_summary =
-                    buffer.text_summary_for_range::<TextSummary, _>(sum.input.bytes..edit.new.end);
+            new_transforms.push_tree(cursor.suffix(&()), &());
+            if new_transforms.is_empty() {
+                let text_summary = new_buffer.text_summary();
                 new_transforms.push(
                     Transform {
                         summary: TransformSummary {
@@ -414,73 +417,59 @@ impl FoldMap {
                     &(),
                 );
             }
-        }
 
-        new_transforms.push_tree(cursor.suffix(&()), &());
-        if new_transforms.is_empty() {
-            let text_summary = buffer.text_summary();
-            new_transforms.push(
-                Transform {
-                    summary: TransformSummary {
-                        output: text_summary.clone(),
-                        input: text_summary,
-                    },
-                    output_text: None,
-                },
-                &(),
-            );
-        }
+            drop(cursor);
 
-        drop(cursor);
+            let mut fold_edits = Vec::with_capacity(buffer_edits.len());
+            {
+                let mut old_transforms = transforms.cursor::<(usize, FoldOffset)>();
+                let mut new_transforms = new_transforms.cursor::<(usize, FoldOffset)>();
 
-        let mut fold_edits = Vec::with_capacity(buffer_edits.len());
-        {
-            let mut old_transforms = transforms.cursor::<(usize, FoldOffset)>();
-            let mut new_transforms = new_transforms.cursor::<(usize, FoldOffset)>();
+                for mut edit in buffer_edits {
+                    old_transforms.seek(&edit.old.start, Bias::Left, &());
+                    if old_transforms.item().map_or(false, |t| t.is_fold()) {
+                        edit.old.start = old_transforms.start().0;
+                    }
+                    let old_start =
+                        old_transforms.start().1 .0 + (edit.old.start - old_transforms.start().0);
 
-            for mut edit in buffer_edits {
-                old_transforms.seek(&edit.old.start, Bias::Left, &());
-                if old_transforms.item().map_or(false, |t| t.is_fold()) {
-                    edit.old.start = old_transforms.start().0;
-                }
-                let old_start =
-                    old_transforms.start().1 .0 + (edit.old.start - old_transforms.start().0);
+                    old_transforms.seek_forward(&edit.old.end, Bias::Right, &());
+                    if old_transforms.item().map_or(false, |t| t.is_fold()) {
+                        old_transforms.next(&());
+                        edit.old.end = old_transforms.start().0;
+                    }
+                    let old_end =
+                        old_transforms.start().1 .0 + (edit.old.end - old_transforms.start().0);
 
-                old_transforms.seek_forward(&edit.old.end, Bias::Right, &());
-                if old_transforms.item().map_or(false, |t| t.is_fold()) {
-                    old_transforms.next(&());
-                    edit.old.end = old_transforms.start().0;
-                }
-                let old_end =
-                    old_transforms.start().1 .0 + (edit.old.end - old_transforms.start().0);
+                    new_transforms.seek(&edit.new.start, Bias::Left, &());
+                    if new_transforms.item().map_or(false, |t| t.is_fold()) {
+                        edit.new.start = new_transforms.start().0;
+                    }
+                    let new_start =
+                        new_transforms.start().1 .0 + (edit.new.start - new_transforms.start().0);
 
-                new_transforms.seek(&edit.new.start, Bias::Left, &());
-                if new_transforms.item().map_or(false, |t| t.is_fold()) {
-                    edit.new.start = new_transforms.start().0;
-                }
-                let new_start =
-                    new_transforms.start().1 .0 + (edit.new.start - new_transforms.start().0);
+                    new_transforms.seek_forward(&edit.new.end, Bias::Right, &());
+                    if new_transforms.item().map_or(false, |t| t.is_fold()) {
+                        new_transforms.next(&());
+                        edit.new.end = new_transforms.start().0;
+                    }
+                    let new_end =
+                        new_transforms.start().1 .0 + (edit.new.end - new_transforms.start().0);
 
-                new_transforms.seek_forward(&edit.new.end, Bias::Right, &());
-                if new_transforms.item().map_or(false, |t| t.is_fold()) {
-                    new_transforms.next(&());
-                    edit.new.end = new_transforms.start().0;
+                    fold_edits.push(FoldEdit {
+                        old_bytes: FoldOffset(old_start)..FoldOffset(old_end),
+                        new_bytes: FoldOffset(new_start)..FoldOffset(new_end),
+                    });
                 }
-                let new_end =
-                    new_transforms.start().1 .0 + (edit.new.end - new_transforms.start().0);
 
-                fold_edits.push(FoldEdit {
-                    old_bytes: FoldOffset(old_start)..FoldOffset(old_end),
-                    new_bytes: FoldOffset(new_start)..FoldOffset(new_end),
-                });
+                consolidate_fold_edits(&mut fold_edits);
             }
 
-            consolidate_fold_edits(&mut fold_edits);
+            *transforms = new_transforms;
+            *self.buffer.lock() = new_buffer;
+            self.version.fetch_add(1, SeqCst);
+            fold_edits
         }
-
-        *transforms = new_transforms;
-        self.version.fetch_add(1, SeqCst);
-        fold_edits
     }
 }
 
@@ -1076,6 +1065,7 @@ impl FoldEdit {
 mod tests {
     use super::*;
     use crate::{test::sample_text, ToPoint};
+    use language::Buffer;
     use rand::prelude::*;
     use std::{env, mem};
     use text::RandomCharIter;
@@ -1084,16 +1074,14 @@ mod tests {
     #[gpui::test]
     fn test_basic_folds(cx: &mut gpui::MutableAppContext) {
         let buffer = cx.add_model(|cx| Buffer::new(0, sample_text(5, 6), cx));
-        let mut map = FoldMap::new(buffer.clone(), cx.as_ref()).0;
-
-        let (mut writer, _, _) = map.write(cx.as_ref());
-        let (snapshot2, edits) = writer.fold(
-            vec![
-                Point::new(0, 2)..Point::new(2, 2),
-                Point::new(2, 4)..Point::new(4, 1),
-            ],
-            cx.as_ref(),
-        );
+        let buffer_snapshot = buffer.read(cx).snapshot();
+        let mut map = FoldMap::new(buffer_snapshot.clone()).0;
+
+        let (mut writer, _, _) = map.write(buffer_snapshot.clone(), vec![]);
+        let (snapshot2, edits) = writer.fold(vec![
+            Point::new(0, 2)..Point::new(2, 2),
+            Point::new(2, 4)..Point::new(4, 1),
+        ]);
         assert_eq!(snapshot2.text(), "aa…cc…eeeee");
         assert_eq!(
             edits,
@@ -1109,7 +1097,8 @@ mod tests {
             ]
         );
 
-        buffer.update(cx, |buffer, cx| {
+        let (buffer_snapshot, edits) = buffer.update(cx, |buffer, cx| {
+            let v0 = buffer.version();
             buffer.edit(
                 vec![
                     Point::new(0, 0)..Point::new(0, 1),
@@ -1118,8 +1107,9 @@ mod tests {
                 "123",
                 cx,
             );
+            (buffer.snapshot(), buffer.edits_since(&v0).collect())
         });
-        let (snapshot3, edits) = map.read(cx.as_ref());
+        let (snapshot3, edits) = map.read(buffer_snapshot.clone(), edits);
         assert_eq!(snapshot3.text(), "123a…c123c…eeeee");
         assert_eq!(
             edits,
@@ -1135,55 +1125,62 @@ mod tests {
             ]
         );
 
-        buffer.update(cx, |buffer, cx| {
-            buffer.edit(vec![Point::new(2, 6)..Point::new(4, 3)], "456", cx)
+        let (buffer_snapshot, edits) = buffer.update(cx, |buffer, cx| {
+            let v0 = buffer.version();
+            buffer.edit(vec![Point::new(2, 6)..Point::new(4, 3)], "456", cx);
+            (buffer.snapshot(), buffer.edits_since(&v0).collect())
         });
-        let (snapshot4, _) = map.read(cx.as_ref());
+        let (snapshot4, _) = map.read(buffer_snapshot.clone(), edits);
         assert_eq!(snapshot4.text(), "123a…c123456eee");
 
-        let (mut writer, _, _) = map.write(cx.as_ref());
-        writer.unfold(Some(Point::new(0, 4)..Point::new(0, 5)), cx.as_ref());
-        let (snapshot5, _) = map.read(cx.as_ref());
+        let (mut writer, _, _) = map.write(buffer_snapshot.clone(), vec![]);
+        writer.unfold(Some(Point::new(0, 4)..Point::new(0, 5)));
+        let (snapshot5, _) = map.read(buffer_snapshot.clone(), vec![]);
         assert_eq!(snapshot5.text(), "123aaaaa\nbbbbbb\nccc123456eee");
     }
 
     #[gpui::test]
     fn test_adjacent_folds(cx: &mut gpui::MutableAppContext) {
         let buffer = cx.add_model(|cx| Buffer::new(0, "abcdefghijkl", cx));
+        let buffer_snapshot = buffer.read(cx).snapshot();
 
         {
-            let mut map = FoldMap::new(buffer.clone(), cx.as_ref()).0;
+            let mut map = FoldMap::new(buffer_snapshot.clone()).0;
 
-            let (mut writer, _, _) = map.write(cx.as_ref());
-            writer.fold(vec![5..8], cx.as_ref());
-            let (snapshot, _) = map.read(cx.as_ref());
+            let (mut writer, _, _) = map.write(buffer_snapshot.clone(), vec![]);
+            writer.fold(vec![5..8]);
+            let (snapshot, _) = map.read(buffer_snapshot.clone(), vec![]);
             assert_eq!(snapshot.text(), "abcde…ijkl");
 
             // Create an fold adjacent to the start of the first fold.
-            let (mut writer, _, _) = map.write(cx.as_ref());
-            writer.fold(vec![0..1, 2..5], cx.as_ref());
-            let (snapshot, _) = map.read(cx.as_ref());
+            let (mut writer, _, _) = map.write(buffer_snapshot.clone(), vec![]);
+            writer.fold(vec![0..1, 2..5]);
+            let (snapshot, _) = map.read(buffer_snapshot.clone(), vec![]);
             assert_eq!(snapshot.text(), "…b…ijkl");
 
             // Create an fold adjacent to the end of the first fold.
-            let (mut writer, _, _) = map.write(cx.as_ref());
-            writer.fold(vec![11..11, 8..10], cx.as_ref());
-            let (snapshot, _) = map.read(cx.as_ref());
+            let (mut writer, _, _) = map.write(buffer_snapshot.clone(), vec![]);
+            writer.fold(vec![11..11, 8..10]);
+            let (snapshot, _) = map.read(buffer_snapshot.clone(), vec![]);
             assert_eq!(snapshot.text(), "…b…kl");
         }
 
         {
-            let mut map = FoldMap::new(buffer.clone(), cx.as_ref()).0;
+            let mut map = FoldMap::new(buffer_snapshot.clone()).0;
 
             // Create two adjacent folds.
-            let (mut writer, _, _) = map.write(cx.as_ref());
-            writer.fold(vec![0..2, 2..5], cx.as_ref());
-            let (snapshot, _) = map.read(cx.as_ref());
+            let (mut writer, _, _) = map.write(buffer_snapshot.clone(), vec![]);
+            writer.fold(vec![0..2, 2..5]);
+            let (snapshot, _) = map.read(buffer_snapshot.clone(), vec![]);
             assert_eq!(snapshot.text(), "…fghijkl");
 
             // Edit within one of the folds.
-            buffer.update(cx, |buffer, cx| buffer.edit(vec![0..1], "12345", cx));
-            let (snapshot, _) = map.read(cx.as_ref());
+            let (buffer_snapshot, edits) = buffer.update(cx, |buffer, cx| {
+                let v0 = buffer.version();
+                buffer.edit(vec![0..1], "12345", cx);
+                (buffer.snapshot(), buffer.edits_since(&v0).collect())
+            });
+            let (snapshot, _) = map.read(buffer_snapshot.clone(), edits);
             assert_eq!(snapshot.text(), "12345…fghijkl");
         }
     }
@@ -1191,61 +1188,57 @@ mod tests {
     #[gpui::test]
     fn test_overlapping_folds(cx: &mut gpui::MutableAppContext) {
         let buffer = cx.add_model(|cx| Buffer::new(0, sample_text(5, 6), cx));
-        let mut map = FoldMap::new(buffer.clone(), cx.as_ref()).0;
-        let (mut writer, _, _) = map.write(cx.as_ref());
-        writer.fold(
-            vec![
-                Point::new(0, 2)..Point::new(2, 2),
-                Point::new(0, 4)..Point::new(1, 0),
-                Point::new(1, 2)..Point::new(3, 2),
-                Point::new(3, 1)..Point::new(4, 1),
-            ],
-            cx.as_ref(),
-        );
-        let (snapshot, _) = map.read(cx.as_ref());
+        let buffer_snapshot = buffer.read(cx).snapshot();
+        let mut map = FoldMap::new(buffer_snapshot.clone()).0;
+        let (mut writer, _, _) = map.write(buffer_snapshot.clone(), vec![]);
+        writer.fold(vec![
+            Point::new(0, 2)..Point::new(2, 2),
+            Point::new(0, 4)..Point::new(1, 0),
+            Point::new(1, 2)..Point::new(3, 2),
+            Point::new(3, 1)..Point::new(4, 1),
+        ]);
+        let (snapshot, _) = map.read(buffer_snapshot.clone(), vec![]);
         assert_eq!(snapshot.text(), "aa…eeeee");
     }
 
     #[gpui::test]
     fn test_merging_folds_via_edit(cx: &mut gpui::MutableAppContext) {
         let buffer = cx.add_model(|cx| Buffer::new(0, sample_text(5, 6), cx));
-        let mut map = FoldMap::new(buffer.clone(), cx.as_ref()).0;
-
-        let (mut writer, _, _) = map.write(cx.as_ref());
-        writer.fold(
-            vec![
-                Point::new(0, 2)..Point::new(2, 2),
-                Point::new(3, 1)..Point::new(4, 1),
-            ],
-            cx.as_ref(),
-        );
-        let (snapshot, _) = map.read(cx.as_ref());
+        let buffer_snapshot = buffer.read(cx).snapshot();
+        let mut map = FoldMap::new(buffer_snapshot.clone()).0;
+
+        let (mut writer, _, _) = map.write(buffer_snapshot.clone(), vec![]);
+        writer.fold(vec![
+            Point::new(0, 2)..Point::new(2, 2),
+            Point::new(3, 1)..Point::new(4, 1),
+        ]);
+        let (snapshot, _) = map.read(buffer_snapshot.clone(), vec![]);
         assert_eq!(snapshot.text(), "aa…cccc\nd…eeeee");
 
-        buffer.update(cx, |buffer, cx| {
-            buffer.edit(Some(Point::new(2, 2)..Point::new(3, 1)), "", cx)
+        let (buffer_snapshot, edits) = buffer.update(cx, |buffer, cx| {
+            let v0 = buffer.version();
+            buffer.edit(Some(Point::new(2, 2)..Point::new(3, 1)), "", cx);
+            (buffer.snapshot(), buffer.edits_since(&v0).collect())
         });
-        let (snapshot, _) = map.read(cx.as_ref());
+        let (snapshot, _) = map.read(buffer_snapshot.clone(), edits);
         assert_eq!(snapshot.text(), "aa…eeeee");
     }
 
     #[gpui::test]
     fn test_folds_in_range(cx: &mut gpui::MutableAppContext) {
         let buffer = cx.add_model(|cx| Buffer::new(0, sample_text(5, 6), cx));
-        let mut map = FoldMap::new(buffer.clone(), cx.as_ref()).0;
+        let buffer_snapshot = buffer.read(cx).snapshot();
+        let mut map = FoldMap::new(buffer_snapshot.clone()).0;
         let buffer = buffer.read(cx);
 
-        let (mut writer, _, _) = map.write(cx.as_ref());
-        writer.fold(
-            vec![
-                Point::new(0, 2)..Point::new(2, 2),
-                Point::new(0, 4)..Point::new(1, 0),
-                Point::new(1, 2)..Point::new(3, 2),
-                Point::new(3, 1)..Point::new(4, 1),
-            ],
-            cx.as_ref(),
-        );
-        let (snapshot, _) = map.read(cx.as_ref());
+        let (mut writer, _, _) = map.write(buffer_snapshot.clone(), vec![]);
+        writer.fold(vec![
+            Point::new(0, 2)..Point::new(2, 2),
+            Point::new(0, 4)..Point::new(1, 0),
+            Point::new(1, 2)..Point::new(3, 2),
+            Point::new(3, 1)..Point::new(4, 1),
+        ]);
+        let (snapshot, _) = map.read(buffer_snapshot.clone(), vec![]);
         let fold_ranges = snapshot
             .folds_in_range(Point::new(1, 0)..Point::new(1, 3))
             .map(|fold| fold.start.to_point(buffer)..fold.end.to_point(buffer))
@@ -1270,37 +1263,41 @@ mod tests {
             let text = RandomCharIter::new(&mut rng).take(len).collect::<String>();
             Buffer::new(0, text, cx)
         });
-        let mut map = FoldMap::new(buffer.clone(), cx.as_ref()).0;
+        let buffer_snapshot = buffer.read(cx).snapshot();
+        let mut map = FoldMap::new(buffer_snapshot.clone()).0;
 
-        let (mut initial_snapshot, _) = map.read(cx.as_ref());
+        let (mut initial_snapshot, _) = map.read(buffer_snapshot.clone(), vec![]);
         let mut snapshot_edits = Vec::new();
 
         for _ in 0..operations {
             log::info!("text: {:?}", buffer.read(cx).text());
-            match rng.gen_range(0..=100) {
+            let buffer_edits = match rng.gen_range(0..=100) {
                 0..=59 => {
-                    snapshot_edits.extend(map.randomly_mutate(&mut rng, cx.as_ref()));
+                    snapshot_edits.extend(map.randomly_mutate(&mut rng));
+                    vec![]
                 }
-                _ => {
-                    let edits = buffer.update(cx, |buffer, _| {
-                        let start_version = buffer.version.clone();
-                        let edit_count = rng.gen_range(1..=5);
-                        buffer.randomly_edit(&mut rng, edit_count);
-                        buffer
-                            .edits_since::<Point>(&start_version)
-                            .collect::<Vec<_>>()
-                    });
+                _ => buffer.update(cx, |buffer, cx| {
+                    let start_version = buffer.version.clone();
+                    let edit_count = rng.gen_range(1..=5);
+                    buffer.randomly_edit(&mut rng, edit_count, cx);
+                    let edits = buffer
+                        .edits_since::<Point>(&start_version)
+                        .collect::<Vec<_>>();
                     log::info!("editing {:?}", edits);
-                }
-            }
+                    buffer.edits_since::<usize>(&start_version).collect()
+                }),
+            };
+            let buffer_snapshot = buffer.read(cx).snapshot();
 
-            let buffer = map.buffer.read(cx).snapshot();
-            let mut expected_text: String = buffer.text().to_string();
+            let (snapshot, edits) = map.read(buffer_snapshot.clone(), buffer_edits);
+            snapshot_edits.push((snapshot.clone(), edits));
+
+            let mut expected_text: String = buffer_snapshot.text().to_string();
             let mut expected_buffer_rows = Vec::new();
-            let mut next_row = buffer.max_point().row;
-            for fold_range in map.merged_fold_ranges(cx.as_ref()).into_iter().rev() {
-                let fold_start = buffer.point_for_offset(fold_range.start).unwrap();
-                let fold_end = buffer.point_for_offset(fold_range.end).unwrap();
+            let mut next_row = buffer_snapshot.max_point().row;
+            for fold_range in map.merged_fold_ranges().into_iter().rev() {
+                let fold_start = buffer_snapshot.point_for_offset(fold_range.start).unwrap();
+                let fold_end = buffer_snapshot.point_for_offset(fold_range.end).unwrap();
                 expected_buffer_rows.extend((fold_end.row + 1..=next_row).rev());
                 next_row = fold_start.row;
 
@@ -1309,9 +1306,7 @@ mod tests {
             expected_buffer_rows.extend((0..=next_row).rev());
             expected_buffer_rows.reverse();
 
-            let (snapshot, edits) = map.read(cx.as_ref());
             assert_eq!(snapshot.text(), expected_text);
-            snapshot_edits.push((snapshot.clone(), edits));
 
             for (output_row, line) in expected_text.lines().enumerate() {
                 let line_len = snapshot.line_len(output_row as u32);
@@ -1330,7 +1325,7 @@ mod tests {
             let mut char_column = 0;
             for c in expected_text.chars() {
                 let buffer_point = fold_point.to_buffer_point(&snapshot);
-                let buffer_offset = buffer_point.to_offset(&buffer);
+                let buffer_offset = buffer_point.to_offset(&buffer_snapshot);
                 assert_eq!(
                     buffer_point.to_fold_point(&snapshot, Right),
                     fold_point,
@@ -1400,26 +1395,28 @@ mod tests {
                 );
             }
 
-            for fold_range in map.merged_fold_ranges(cx.as_ref()) {
+            for fold_range in map.merged_fold_ranges() {
                 let fold_point = fold_range
                     .start
-                    .to_point(&buffer)
+                    .to_point(&buffer_snapshot)
                     .to_fold_point(&snapshot, Right);
                 assert!(snapshot.is_line_folded(fold_point.row()));
             }
 
             for _ in 0..5 {
-                let end = buffer.clip_offset(rng.gen_range(0..=buffer.len()), Right);
-                let start = buffer.clip_offset(rng.gen_range(0..=end), Left);
+                let end =
+                    buffer_snapshot.clip_offset(rng.gen_range(0..=buffer_snapshot.len()), Right);
+                let start = buffer_snapshot.clip_offset(rng.gen_range(0..=end), Left);
                 let expected_folds = map
                     .folds
-                    .items(&buffer)
+                    .items(&buffer_snapshot)
                     .into_iter()
                     .filter(|fold| {
-                        let start = buffer.anchor_before(start);
-                        let end = buffer.anchor_after(end);
-                        start.cmp(&fold.0.end, &buffer).unwrap() == Ordering::Less
-                            && end.cmp(&fold.0.start, &buffer).unwrap() == Ordering::Greater
+                        let start = buffer_snapshot.anchor_before(start);
+                        let end = buffer_snapshot.anchor_after(end);
+                        start.cmp(&fold.0.end, &buffer_snapshot).unwrap() == Ordering::Less
+                            && end.cmp(&fold.0.start, &buffer_snapshot).unwrap()
+                                == Ordering::Greater
                     })
                     .map(|fold| fold.0)
                     .collect::<Vec<_>>();
@@ -1477,26 +1474,24 @@ mod tests {
         let text = sample_text(6, 6) + "\n";
         let buffer = cx.add_model(|cx| Buffer::new(0, text, cx));
 
-        let mut map = FoldMap::new(buffer.clone(), cx.as_ref()).0;
+        let buffer_snapshot = buffer.read(cx).snapshot();
+        let mut map = FoldMap::new(buffer_snapshot.clone()).0;
 
-        let (mut writer, _, _) = map.write(cx.as_ref());
-        writer.fold(
-            vec![
-                Point::new(0, 2)..Point::new(2, 2),
-                Point::new(3, 1)..Point::new(4, 1),
-            ],
-            cx.as_ref(),
-        );
+        let (mut writer, _, _) = map.write(buffer_snapshot.clone(), vec![]);
+        writer.fold(vec![
+            Point::new(0, 2)..Point::new(2, 2),
+            Point::new(3, 1)..Point::new(4, 1),
+        ]);
 
-        let (snapshot, _) = map.read(cx.as_ref());
+        let (snapshot, _) = map.read(buffer_snapshot.clone(), vec![]);
         assert_eq!(snapshot.text(), "aa…cccc\nd…eeeee\nffffff\n");
         assert_eq!(snapshot.buffer_rows(0).collect::<Vec<_>>(), [0, 3, 5, 6]);
         assert_eq!(snapshot.buffer_rows(3).collect::<Vec<_>>(), [6]);
     }
 
     impl FoldMap {
-        fn merged_fold_ranges(&self, cx: &AppContext) -> Vec<Range<usize>> {
-            let buffer = self.buffer.read(cx).snapshot();
+        fn merged_fold_ranges(&self) -> Vec<Range<usize>> {
+            let buffer = self.buffer.lock().clone();
             let mut folds = self.folds.items(&buffer);
             // Ensure sorting doesn't change how folds get merged and displayed.
             folds.sort_by(|a, b| a.0.cmp(&b.0, &buffer).unwrap());
@@ -1524,15 +1519,11 @@ mod tests {
             merged_ranges
         }
 
-        pub fn randomly_mutate(
-            &mut self,
-            rng: &mut impl Rng,
-            cx: &AppContext,
-        ) -> Vec<(Snapshot, Vec<FoldEdit>)> {
+        pub fn randomly_mutate(&mut self, rng: &mut impl Rng) -> Vec<(Snapshot, Vec<FoldEdit>)> {
             let mut snapshot_edits = Vec::new();
             match rng.gen_range(0..=100) {
                 0..=39 if !self.folds.is_empty() => {
-                    let buffer = self.buffer.read(cx);
+                    let buffer = self.buffer.lock().clone();
                     let mut to_unfold = Vec::new();
                     for _ in 0..rng.gen_range(1..=3) {
                         let end = buffer.clip_offset(rng.gen_range(0..=buffer.len()), Right);
@@ -1540,13 +1531,13 @@ mod tests {
                         to_unfold.push(start..end);
                     }
                     log::info!("unfolding {:?}", to_unfold);
-                    let (mut writer, snapshot, edits) = self.write(cx.as_ref());
+                    let (mut writer, snapshot, edits) = self.write(buffer, vec![]);
                     snapshot_edits.push((snapshot, edits));
-                    let (snapshot, edits) = writer.fold(to_unfold, cx.as_ref());
+                    let (snapshot, edits) = writer.fold(to_unfold);
                     snapshot_edits.push((snapshot, edits));
                 }
                 _ => {
-                    let buffer = self.buffer.read(cx);
+                    let buffer = self.buffer.lock().clone();
                     let mut to_fold = Vec::new();
                     for _ in 0..rng.gen_range(1..=2) {
                         let end = buffer.clip_offset(rng.gen_range(0..=buffer.len()), Right);
@@ -1554,9 +1545,9 @@ mod tests {
                         to_fold.push(start..end);
                     }
                     log::info!("folding {:?}", to_fold);
-                    let (mut writer, snapshot, edits) = self.write(cx.as_ref());
+                    let (mut writer, snapshot, edits) = self.write(buffer, vec![]);
                     snapshot_edits.push((snapshot, edits));
-                    let (snapshot, edits) = writer.fold(to_fold, cx.as_ref());
+                    let (snapshot, edits) = writer.fold(to_fold);
                     snapshot_edits.push((snapshot, edits));
                 }
             }

crates/editor/src/display_map/tab_map.rs 🔗

@@ -470,11 +470,12 @@ mod tests {
             let text = RandomCharIter::new(&mut rng).take(len).collect::<String>();
             Buffer::new(0, text, cx)
         });
+        let buffer_snapshot = buffer.read(cx).snapshot();
         log::info!("Buffer text: {:?}", buffer.read(cx).text());
 
-        let (mut fold_map, _) = FoldMap::new(buffer.clone(), cx);
-        fold_map.randomly_mutate(&mut rng, cx);
-        let (folds_snapshot, _) = fold_map.read(cx);
+        let (mut fold_map, _) = FoldMap::new(buffer_snapshot.clone());
+        fold_map.randomly_mutate(&mut rng);
+        let (folds_snapshot, _) = fold_map.read(buffer_snapshot.clone(), vec![]);
         log::info!("FoldMap text: {:?}", folds_snapshot.text());
 
         let (_, tabs_snapshot) = TabMap::new(folds_snapshot.clone(), tab_size);

crates/editor/src/display_map/wrap_map.rs 🔗

@@ -1,6 +1,5 @@
 use super::{
     fold_map,
-    patch::Patch,
     tab_map::{self, Edit as TabEdit, Snapshot as TabSnapshot, TabPoint},
     DisplayRow,
 };
@@ -13,6 +12,7 @@ use lazy_static::lazy_static;
 use smol::future::yield_now;
 use std::{collections::VecDeque, mem, ops::Range, time::Duration};
 use sum_tree::{Bias, Cursor, SumTree};
+use text::Patch;
 use theme::SyntaxTheme;
 
 pub use super::tab_map::TextSummary;
@@ -21,8 +21,8 @@ pub type Edit = text::Edit<u32>;
 pub struct WrapMap {
     snapshot: Snapshot,
     pending_edits: VecDeque<(TabSnapshot, Vec<TabEdit>)>,
-    interpolated_edits: Patch,
-    edits_since_sync: Patch,
+    interpolated_edits: Patch<u32>,
+    edits_since_sync: Patch<u32>,
     wrap_width: Option<f32>,
     background_task: Option<Task<()>>,
     font: (FontId, f32),
@@ -204,12 +204,10 @@ impl WrapMap {
             }
             let new_rows = self.snapshot.transforms.summary().output.lines.row + 1;
             self.snapshot.interpolated = false;
-            self.edits_since_sync = self.edits_since_sync.compose(&unsafe {
-                Patch::new_unchecked(vec![Edit {
-                    old: 0..old_rows,
-                    new: 0..new_rows,
-                }])
-            });
+            self.edits_since_sync = self.edits_since_sync.compose(&Patch::new(vec![Edit {
+                old: 0..old_rows,
+                new: 0..new_rows,
+            }]));
         }
     }
 
@@ -308,7 +306,7 @@ impl Snapshot {
         }
     }
 
-    fn interpolate(&mut self, new_tab_snapshot: TabSnapshot, tab_edits: &[TabEdit]) -> Patch {
+    fn interpolate(&mut self, new_tab_snapshot: TabSnapshot, tab_edits: &[TabEdit]) -> Patch<u32> {
         let mut new_transforms;
         if tab_edits.is_empty() {
             new_transforms = self.transforms.clone();
@@ -383,7 +381,7 @@ impl Snapshot {
         tab_edits: &[TabEdit],
         wrap_width: f32,
         line_wrapper: &mut LineWrapper,
-    ) -> Patch {
+    ) -> Patch<u32> {
         #[derive(Debug)]
         struct RowEdit {
             old_rows: Range<u32>,
@@ -526,7 +524,7 @@ impl Snapshot {
         old_snapshot.compute_edits(tab_edits, self)
     }
 
-    fn compute_edits(&self, tab_edits: &[TabEdit], new_snapshot: &Snapshot) -> Patch {
+    fn compute_edits(&self, tab_edits: &[TabEdit], new_snapshot: &Snapshot) -> Patch<u32> {
         let mut wrap_edits = Vec::new();
         let mut old_cursor = self.transforms.cursor::<TransformSummary>();
         let mut new_cursor = new_snapshot.transforms.cursor::<TransformSummary>();
@@ -559,7 +557,7 @@ impl Snapshot {
         }
 
         consolidate_wrap_edits(&mut wrap_edits);
-        unsafe { Patch::new_unchecked(wrap_edits) }
+        Patch::new(wrap_edits)
     }
 
     pub fn text_chunks(&self, wrap_row: u32) -> impl Iterator<Item = &str> {
@@ -1026,7 +1024,8 @@ mod tests {
             let text = RandomCharIter::new(&mut rng).take(len).collect::<String>();
             Buffer::new(0, text, cx)
         });
-        let (mut fold_map, folds_snapshot) = cx.read(|cx| FoldMap::new(buffer.clone(), cx));
+        let buffer_snapshot = buffer.read_with(&cx, |buffer, _| buffer.snapshot());
+        let (mut fold_map, folds_snapshot) = FoldMap::new(buffer_snapshot.clone());
         let (tab_map, tabs_snapshot) = TabMap::new(folds_snapshot.clone(), tab_size);
         log::info!(
             "Unwrapped text (no folds): {:?}",
@@ -1067,6 +1066,7 @@ mod tests {
         for _i in 0..operations {
             log::info!("{} ==============================================", _i);
 
+            let mut buffer_edits = Vec::new();
             match rng.gen_range(0..=100) {
                 0..=19 => {
                     wrap_width = if rng.gen_bool(0.2) {
@@ -1078,9 +1078,7 @@ mod tests {
                     wrap_map.update(&mut cx, |map, cx| map.set_wrap_width(wrap_width, cx));
                 }
                 20..=39 => {
-                    for (folds_snapshot, fold_edits) in
-                        cx.read(|cx| fold_map.randomly_mutate(&mut rng, cx))
-                    {
+                    for (folds_snapshot, fold_edits) in fold_map.randomly_mutate(&mut rng) {
                         let (tabs_snapshot, tab_edits) = tab_map.sync(folds_snapshot, fold_edits);
                         let (mut snapshot, wrap_edits) = wrap_map
                             .update(&mut cx, |map, cx| map.sync(tabs_snapshot, tab_edits, cx));
@@ -1090,15 +1088,18 @@ mod tests {
                     }
                 }
                 _ => {
-                    buffer.update(&mut cx, |buffer, _| buffer.randomly_mutate(&mut rng));
+                    buffer.update(&mut cx, |buffer, cx| {
+                        let v0 = buffer.version();
+                        let edit_count = rng.gen_range(1..=5);
+                        buffer.randomly_edit(&mut rng, edit_count, cx);
+                        buffer_edits.extend(buffer.edits_since(&v0));
+                    });
                 }
             }
 
-            log::info!(
-                "Unwrapped text (no folds): {:?}",
-                buffer.read_with(&cx, |buf, _| buf.text())
-            );
-            let (folds_snapshot, fold_edits) = cx.read(|cx| fold_map.read(cx));
+            let buffer_snapshot = buffer.read_with(&cx, |buffer, _| buffer.snapshot());
+            log::info!("Unwrapped text (no folds): {:?}", buffer_snapshot.text());
+            let (folds_snapshot, fold_edits) = fold_map.read(buffer_snapshot, buffer_edits);
             log::info!(
                 "Unwrapped text (unexpanded tabs): {:?}",
                 folds_snapshot.text()

crates/editor/src/editor.rs 🔗

@@ -3472,7 +3472,7 @@ impl Editor {
             language::Event::FileHandleChanged => cx.emit(Event::FileHandleChanged),
             language::Event::Reloaded => cx.emit(Event::FileHandleChanged),
             language::Event::Closed => cx.emit(Event::Closed),
-            language::Event::Reparsed => {}
+            _ => {}
         }
     }
 

crates/language/src/buffer.rs 🔗

@@ -72,8 +72,10 @@ pub struct Snapshot {
     text: text::Snapshot,
     tree: Option<Tree>,
     diagnostics: AnchorRangeMultimap<Diagnostic>,
+    diagnostics_update_count: usize,
     is_parsing: bool,
     language: Option<Arc<Language>>,
+    parse_count: usize,
 }
 
 #[derive(Clone, Debug, PartialEq, Eq)]
@@ -113,6 +115,7 @@ pub enum Event {
     FileHandleChanged,
     Reloaded,
     Reparsed,
+    DiagnosticsUpdated,
     Closed,
 }
 
@@ -338,8 +341,10 @@ impl Buffer {
             text: self.text.snapshot(),
             tree: self.syntax_tree(),
             diagnostics: self.diagnostics.clone(),
+            diagnostics_update_count: self.diagnostics_update_count,
             is_parsing: self.parsing_in_background,
             language: self.language.clone(),
+            parse_count: self.parse_count,
         }
     }
 
@@ -805,6 +810,7 @@ impl Buffer {
 
         self.diagnostics_update_count += 1;
         cx.notify();
+        cx.emit(Event::DiagnosticsUpdated);
         Ok(Operation::UpdateDiagnostics(self.diagnostics.clone()))
     }
 
@@ -1132,6 +1138,10 @@ impl Buffer {
                 .map_or(false, |file| file.mtime() > self.saved_mtime)
     }
 
+    pub fn subscribe(&mut self) -> Subscription {
+        self.text.subscribe()
+    }
+
     pub fn start_transaction(
         &mut self,
         selection_set_ids: impl IntoIterator<Item = SelectionSetId>,
@@ -1316,7 +1326,8 @@ impl Buffer {
         was_dirty: bool,
         cx: &mut ModelContext<Self>,
     ) {
-        if self.edits_since::<usize>(old_version).next().is_none() {
+        let patch = Patch::new(self.edits_since::<usize>(old_version).collect());
+        if patch.is_empty() {
             return;
         }
 
@@ -1461,18 +1472,26 @@ impl Buffer {
 
 #[cfg(any(test, feature = "test-support"))]
 impl Buffer {
-    pub fn randomly_edit<T>(&mut self, rng: &mut T, old_range_count: usize)
-    where
+    pub fn randomly_edit<T>(
+        &mut self,
+        rng: &mut T,
+        old_range_count: usize,
+        cx: &mut ModelContext<Self>,
+    ) where
         T: rand::Rng,
     {
+        self.start_transaction(None).unwrap();
         self.text.randomly_edit(rng, old_range_count);
+        self.end_transaction(None, cx).unwrap();
     }
 
-    pub fn randomly_mutate<T>(&mut self, rng: &mut T)
+    pub fn randomly_mutate<T>(&mut self, rng: &mut T, cx: &mut ModelContext<Self>)
     where
         T: rand::Rng,
     {
+        self.start_transaction(None).unwrap();
         self.text.randomly_mutate(rng);
+        self.end_transaction(None, cx).unwrap();
     }
 }
 
@@ -1486,30 +1505,6 @@ impl Entity for Buffer {
     }
 }
 
-// TODO: Do we need to clone a buffer?
-impl Clone for Buffer {
-    fn clone(&self) -> Self {
-        Self {
-            text: self.text.clone(),
-            saved_version: self.saved_version.clone(),
-            saved_mtime: self.saved_mtime,
-            file: self.file.as_ref().map(|f| f.boxed_clone()),
-            language: self.language.clone(),
-            syntax_tree: Mutex::new(self.syntax_tree.lock().clone()),
-            parsing_in_background: false,
-            sync_parse_timeout: self.sync_parse_timeout,
-            parse_count: self.parse_count,
-            autoindent_requests: Default::default(),
-            pending_autoindent: Default::default(),
-            diagnostics: self.diagnostics.clone(),
-            diagnostics_update_count: self.diagnostics_update_count,
-            language_server: None,
-            #[cfg(test)]
-            operations: self.operations.clone(),
-        }
-    }
-}
-
 impl Deref for Buffer {
     type Target = TextBuffer;
 
@@ -1699,6 +1694,14 @@ impl Snapshot {
             .as_ref()
             .and_then(|language| language.grammar.as_ref())
     }
+
+    pub fn diagnostics_update_count(&self) -> usize {
+        self.diagnostics_update_count
+    }
+
+    pub fn parse_count(&self) -> usize {
+        self.parse_count
+    }
 }
 
 impl Clone for Snapshot {
@@ -1707,8 +1710,10 @@ impl Clone for Snapshot {
             text: self.text.clone(),
             tree: self.tree.clone(),
             diagnostics: self.diagnostics.clone(),
+            diagnostics_update_count: self.diagnostics_update_count,
             is_parsing: self.is_parsing,
             language: self.language.clone(),
+            parse_count: self.parse_count,
         }
     }
 }

crates/project/src/worktree.rs 🔗

@@ -20,7 +20,6 @@ use postage::{
     prelude::{Sink as _, Stream as _},
     watch,
 };
-
 use serde::Deserialize;
 use smol::channel::{self, Sender};
 use std::{
@@ -3495,14 +3494,14 @@ mod tests {
                 &[
                     language::Event::Edited,
                     language::Event::Dirtied,
-                    language::Event::Edited
+                    language::Event::Edited,
                 ],
             );
             events.borrow_mut().clear();
 
             // TODO - currently, after restoring the buffer to its
             // previously-saved state, the is still considered dirty.
-            buffer.edit(vec![1..3], "", cx);
+            buffer.edit([1..3], "", cx);
             assert!(buffer.text() == "ac");
             assert!(buffer.is_dirty());
         });

crates/text/Cargo.toml 🔗

@@ -16,10 +16,13 @@ sum_tree = { path = "../sum_tree" }
 anyhow = "1.0.38"
 arrayvec = "0.7.1"
 log = "0.4"
+parking_lot = "0.11"
 rand = { version = "0.8.3", optional = true }
 smallvec = { version = "1.6", features = ["union"] }
 
 [dev-dependencies]
 collections = { path = "../collections", features = ["test-support"] }
 gpui = { path = "../gpui", features = ["test-support"] }
+ctor = "0.1"
+env_logger = "0.8"
 rand = "0.8.3"

crates/editor/src/display_map/patch.rs → crates/text/src/patch.rs 🔗

@@ -1,16 +1,39 @@
-use std::{cmp, mem};
-
-type Edit = text::Edit<u32>;
-
-#[derive(Default, Debug, PartialEq, Eq)]
-pub struct Patch(Vec<Edit>);
-
-impl Patch {
-    pub unsafe fn new_unchecked(edits: Vec<Edit>) -> Self {
+use crate::Edit;
+use std::{
+    cmp, mem,
+    ops::{Add, AddAssign, Sub},
+};
+
+#[derive(Clone, Default, Debug, PartialEq, Eq)]
+pub struct Patch<T>(Vec<Edit<T>>);
+
+impl<T> Patch<T>
+where
+    T: Clone
+        + Copy
+        + Ord
+        + Sub<T, Output = T>
+        + Add<T, Output = T>
+        + AddAssign
+        + Default
+        + PartialEq,
+{
+    pub fn new(edits: Vec<Edit<T>>) -> Self {
+        #[cfg(debug_assertions)]
+        {
+            let mut last_edit: Option<&Edit<T>> = None;
+            for edit in &edits {
+                if let Some(last_edit) = last_edit {
+                    assert!(edit.old.start > last_edit.old.end);
+                    assert!(edit.new.start > last_edit.new.end);
+                }
+                last_edit = Some(edit);
+            }
+        }
         Self(edits)
     }
 
-    pub fn into_inner(self) -> Vec<Edit> {
+    pub fn into_inner(self) -> Vec<Edit<T>> {
         self.0
     }
 
@@ -19,8 +42,8 @@ impl Patch {
         let mut new_edits_iter = other.0.iter().cloned().peekable();
         let mut composed = Patch(Vec::new());
 
-        let mut old_start = 0;
-        let mut new_start = 0;
+        let mut old_start = T::default();
+        let mut new_start = T::default();
         loop {
             let old_edit = old_edits_iter.peek_mut();
             let new_edit = new_edits_iter.peek_mut();
@@ -33,8 +56,8 @@ impl Patch {
                     old_start += catchup;
                     new_start += catchup;
 
-                    let old_end = old_start + old_edit.old.len() as u32;
-                    let new_end = new_start + old_edit.new.len() as u32;
+                    let old_end = old_start + old_edit.old_len();
+                    let new_end = new_start + old_edit.new_len();
                     composed.push(Edit {
                         old: old_start..old_end,
                         new: new_start..new_end,
@@ -54,8 +77,8 @@ impl Patch {
                     old_start += catchup;
                     new_start += catchup;
 
-                    let old_end = old_start + new_edit.old.len() as u32;
-                    let new_end = new_start + new_edit.new.len() as u32;
+                    let old_end = old_start + new_edit.old_len();
+                    let new_end = new_start + new_edit.new_len();
                     composed.push(Edit {
                         old: old_start..old_end,
                         new: new_start..new_end,
@@ -82,7 +105,7 @@ impl Patch {
                         new: new_start..new_end,
                     });
 
-                    old_edit.old.start += overshoot;
+                    old_edit.old.start = old_end;
                     old_edit.new.start += overshoot;
                     old_start = old_end;
                     new_start = new_end;
@@ -100,15 +123,14 @@ impl Patch {
                     });
 
                     new_edit.old.start += overshoot;
-                    new_edit.new.start += overshoot;
+                    new_edit.new.start = new_end;
                     old_start = old_end;
                     new_start = new_end;
                 }
 
                 if old_edit.new.end > new_edit.old.end {
-                    let old_end =
-                        old_start + cmp::min(old_edit.old.len() as u32, new_edit.old.len() as u32);
-                    let new_end = new_start + new_edit.new.len() as u32;
+                    let old_end = old_start + cmp::min(old_edit.old_len(), new_edit.old_len());
+                    let new_end = new_start + new_edit.new_len();
                     composed.push(Edit {
                         old: old_start..old_end,
                         new: new_start..new_end,
@@ -120,9 +142,8 @@ impl Patch {
                     new_start = new_end;
                     new_edits_iter.next();
                 } else {
-                    let old_end = old_start + old_edit.old.len() as u32;
-                    let new_end =
-                        new_start + cmp::min(old_edit.new.len() as u32, new_edit.new.len() as u32);
+                    let old_end = old_start + old_edit.old_len();
+                    let new_end = new_start + cmp::min(old_edit.new_len(), new_edit.new_len());
                     composed.push(Edit {
                         old: old_start..old_end,
                         new: new_start..new_end,
@@ -153,8 +174,12 @@ impl Patch {
         self.0.clear();
     }
 
-    fn push(&mut self, edit: Edit) {
-        if edit.old.len() == 0 && edit.new.len() == 0 {
+    pub fn is_empty(&self) -> bool {
+        self.0.is_empty()
+    }
+
+    pub fn push(&mut self, edit: Edit<T>) {
+        if edit.is_empty() {
             return;
         }
 
@@ -479,7 +504,7 @@ mod tests {
     }
 
     #[track_caller]
-    fn assert_patch_composition(old: Patch, new: Patch, composed: Patch) {
+    fn assert_patch_composition(old: Patch<u32>, new: Patch<u32>, composed: Patch<u32>) {
         let original = ('a'..'z').collect::<Vec<_>>();
         let inserted = ('A'..'Z').collect::<Vec<_>>();
 
@@ -498,7 +523,7 @@ mod tests {
         assert_eq!(old.compose(&new), composed);
     }
 
-    fn apply_patch(text: &mut Vec<char>, patch: &Patch, new_text: &[char]) {
+    fn apply_patch(text: &mut Vec<char>, patch: &Patch<u32>, new_text: &[char]) {
         for edit in patch.0.iter().rev() {
             text.splice(
                 edit.old.start as usize..edit.old.end as usize,

crates/text/src/tests.rs 🔗

@@ -8,6 +8,13 @@ use std::{
     time::{Duration, Instant},
 };
 
+#[cfg(test)]
+#[ctor::ctor]
+fn init_logger() {
+    // std::env::set_var("RUST_LOG", "info");
+    env_logger::init();
+}
+
 #[test]
 fn test_edit() {
     let mut buffer = Buffer::new(0, 0, History::new("abc".into()));
@@ -72,30 +79,43 @@ fn test_random_edits(mut rng: StdRng) {
         );
 
         if rng.gen_bool(0.3) {
-            buffer_versions.push(buffer.clone());
+            buffer_versions.push((buffer.clone(), buffer.subscribe()));
         }
     }
 
-    for mut old_buffer in buffer_versions {
+    for (old_buffer, subscription) in buffer_versions {
         let edits = buffer
             .edits_since::<usize>(&old_buffer.version)
             .collect::<Vec<_>>();
 
         log::info!(
-            "mutating old buffer version {:?}, text: {:?}, edits since: {:?}",
+            "applying edits since version {:?} to old text: {:?}: {:?}",
             old_buffer.version(),
             old_buffer.text(),
             edits,
         );
 
+        let mut text = old_buffer.visible_text.clone();
         for edit in edits {
             let new_text: String = buffer.text_for_range(edit.new.clone()).collect();
-            old_buffer.edit(
-                Some(edit.new.start..edit.new.start + edit.old.len()),
-                new_text,
-            );
+            text.replace(edit.new.start..edit.new.start + edit.old.len(), &new_text);
+        }
+        assert_eq!(text.to_string(), buffer.text());
+
+        let subscription_edits = subscription.consume();
+        log::info!(
+            "applying subscription edits since version {:?} to old text: {:?}: {:?}",
+            old_buffer.version(),
+            old_buffer.text(),
+            subscription_edits,
+        );
+
+        let mut text = old_buffer.visible_text.clone();
+        for edit in subscription_edits.into_inner() {
+            let new_text: String = buffer.text_for_range(edit.new.clone()).collect();
+            text.replace(edit.new.start..edit.new.start + edit.old.len(), &new_text);
         }
-        assert_eq!(old_buffer.text(), buffer.text());
+        assert_eq!(text.to_string(), buffer.text());
     }
 }
 

crates/text/src/text.rs 🔗

@@ -1,5 +1,6 @@
 mod anchor;
 mod operation_queue;
+mod patch;
 mod point;
 mod point_utf16;
 #[cfg(any(test, feature = "test-support"))]
@@ -14,6 +15,8 @@ use anyhow::{anyhow, Result};
 use clock::ReplicaId;
 use collections::{HashMap, HashSet};
 use operation_queue::OperationQueue;
+use parking_lot::Mutex;
+pub use patch::Patch;
 pub use point::*;
 pub use point_utf16::*;
 #[cfg(any(test, feature = "test-support"))]
@@ -24,15 +27,14 @@ pub use selection::*;
 use std::{
     cmp::{self, Reverse},
     iter::Iterator,
-    ops::{self, Deref, Range},
+    ops::{self, Deref, Range, Sub},
     str,
-    sync::Arc,
+    sync::{Arc, Weak},
     time::{Duration, Instant},
 };
 pub use sum_tree::Bias;
 use sum_tree::{FilterCursor, SumTree};
 
-#[derive(Clone)]
 pub struct Buffer {
     snapshot: Snapshot,
     last_edit: clock::Local,
@@ -44,6 +46,7 @@ pub struct Buffer {
     remote_id: u64,
     local_clock: clock::Local,
     lamport_clock: clock::Lamport,
+    subscriptions: Vec<Weak<Mutex<Vec<Patch<usize>>>>>,
 }
 
 #[derive(Clone)]
@@ -307,6 +310,23 @@ pub struct Edit<D> {
     pub new: Range<D>,
 }
 
+impl<D> Edit<D>
+where
+    D: Sub<D, Output = D> + PartialEq + Copy,
+{
+    pub fn old_len(&self) -> D {
+        self.old.end - self.old.start
+    }
+
+    pub fn new_len(&self) -> D {
+        self.new.end - self.new.start
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.old.start == self.old.end && self.new.start == self.new.end
+    }
+}
+
 impl<D1, D2> Edit<(D1, D2)> {
     pub fn flatten(self) -> (Edit<D1>, Edit<D2>) {
         (
@@ -322,6 +342,20 @@ impl<D1, D2> Edit<(D1, D2)> {
     }
 }
 
+#[derive(Clone, Default)]
+pub struct Subscription(Arc<Mutex<Vec<Patch<usize>>>>);
+
+impl Subscription {
+    pub fn consume(&self) -> Patch<usize> {
+        let mut patches = self.0.lock();
+        let mut changes = Patch::default();
+        for patch in patches.drain(..) {
+            changes = changes.compose(&patch);
+        }
+        changes
+    }
+}
+
 #[derive(Copy, Clone, Debug, Default, Eq, PartialEq)]
 pub struct InsertionTimestamp {
     pub replica_id: ReplicaId,
@@ -454,13 +488,14 @@ impl Buffer {
             },
             last_edit: clock::Local::default(),
             history,
-            selections: HashMap::default(),
+            selections: Default::default(),
             deferred_ops: OperationQueue::new(),
             deferred_replicas: HashSet::default(),
             replica_id,
             remote_id,
             local_clock,
             lamport_clock,
+            subscriptions: Default::default(),
         }
     }
 
@@ -527,7 +562,8 @@ impl Buffer {
         new_text: Option<String>,
         timestamp: InsertionTimestamp,
     ) -> EditOperation {
-        let mut edit = EditOperation {
+        let mut edits = Patch::default();
+        let mut edit_op = EditOperation {
             timestamp,
             version: self.version(),
             ranges: Vec::with_capacity(ranges.len()),
@@ -583,6 +619,11 @@ impl Buffer {
 
             // Insert the new text before any existing fragments within the range.
             if let Some(new_text) = new_text.as_deref() {
+                let new_start = new_fragments.summary().text.visible;
+                edits.push(Edit {
+                    old: fragment_start..fragment_start,
+                    new: new_start..new_start + new_text.len(),
+                });
                 new_ropes.push_str(new_text);
                 new_fragments.push(
                     Fragment {
@@ -609,6 +650,13 @@ impl Buffer {
                     intersection.visible = false;
                 }
                 if intersection.len > 0 {
+                    if fragment.visible && !intersection.visible {
+                        let new_start = new_fragments.summary().text.visible;
+                        edits.push(Edit {
+                            old: fragment_start..intersection_end,
+                            new: new_start..new_start,
+                        });
+                    }
                     new_ropes.push_fragment(&intersection, fragment.visible);
                     new_fragments.push(intersection, &None);
                     fragment_start = intersection_end;
@@ -619,7 +667,7 @@ impl Buffer {
             }
 
             let full_range_end = FullOffset(range.end + old_fragments.start().deleted);
-            edit.ranges.push(full_range_start..full_range_end);
+            edit_op.ranges.push(full_range_start..full_range_end);
         }
 
         // If the current fragment has been partially consumed, then consume the rest of it
@@ -644,8 +692,9 @@ impl Buffer {
         self.snapshot.fragments = new_fragments;
         self.snapshot.visible_text = visible_text;
         self.snapshot.deleted_text = deleted_text;
-        edit.new_text = new_text;
-        edit
+        self.update_subscriptions(edits);
+        edit_op.new_text = new_text;
+        edit_op
     }
 
     pub fn apply_ops<I: IntoIterator<Item = Operation>>(&mut self, ops: I) -> Result<()> {
@@ -745,10 +794,11 @@ impl Buffer {
             return;
         }
 
+        let mut edits = Patch::default();
         let cx = Some(version.clone());
         let mut new_ropes =
             RopeBuilder::new(self.visible_text.cursor(0), self.deleted_text.cursor(0));
-        let mut old_fragments = self.fragments.cursor::<VersionedFullOffset>();
+        let mut old_fragments = self.fragments.cursor::<(VersionedFullOffset, usize)>();
         let mut new_fragments = old_fragments.slice(
             &VersionedFullOffset::Offset(ranges[0].start),
             Bias::Left,
@@ -756,16 +806,16 @@ impl Buffer {
         );
         new_ropes.push_tree(new_fragments.summary().text);
 
-        let mut fragment_start = old_fragments.start().full_offset();
+        let mut fragment_start = old_fragments.start().0.full_offset();
         for range in ranges {
-            let fragment_end = old_fragments.end(&cx).full_offset();
+            let fragment_end = old_fragments.end(&cx).0.full_offset();
 
             // If the current fragment ends before this range, then jump ahead to the first fragment
             // that extends past the start of this range, reusing any intervening fragments.
             if fragment_end < range.start {
                 // If the current fragment has been partially consumed, then consume the rest of it
                 // and advance to the next fragment before slicing.
-                if fragment_start > old_fragments.start().full_offset() {
+                if fragment_start > old_fragments.start().0.full_offset() {
                     if fragment_end > fragment_start {
                         let mut suffix = old_fragments.item().unwrap().clone();
                         suffix.len = fragment_end.0 - fragment_start.0;
@@ -779,18 +829,18 @@ impl Buffer {
                     old_fragments.slice(&VersionedFullOffset::Offset(range.start), Bias::Left, &cx);
                 new_ropes.push_tree(slice.summary().text);
                 new_fragments.push_tree(slice, &None);
-                fragment_start = old_fragments.start().full_offset();
+                fragment_start = old_fragments.start().0.full_offset();
             }
 
             // If we are at the end of a non-concurrent fragment, advance to the next one.
-            let fragment_end = old_fragments.end(&cx).full_offset();
+            let fragment_end = old_fragments.end(&cx).0.full_offset();
             if fragment_end == range.start && fragment_end > fragment_start {
                 let mut fragment = old_fragments.item().unwrap().clone();
                 fragment.len = fragment_end.0 - fragment_start.0;
                 new_ropes.push_fragment(&fragment, fragment.visible);
                 new_fragments.push(fragment, &None);
                 old_fragments.next(&cx);
-                fragment_start = old_fragments.start().full_offset();
+                fragment_start = old_fragments.start().0.full_offset();
             }
 
             // Skip over insertions that are concurrent to this edit, but have a lower lamport
@@ -820,6 +870,15 @@ impl Buffer {
 
             // Insert the new text before any existing fragments within the range.
             if let Some(new_text) = new_text {
+                let mut old_start = old_fragments.start().1;
+                if old_fragments.item().map_or(false, |f| f.visible) {
+                    old_start += fragment_start.0 - old_fragments.start().0.full_offset().0;
+                }
+                let new_start = new_fragments.summary().text.visible;
+                edits.push(Edit {
+                    old: old_start..old_start,
+                    new: new_start..new_start + new_text.len(),
+                });
                 new_ropes.push_str(new_text);
                 new_fragments.push(
                     Fragment {
@@ -837,7 +896,7 @@ impl Buffer {
             // portions as deleted.
             while fragment_start < range.end {
                 let fragment = old_fragments.item().unwrap();
-                let fragment_end = old_fragments.end(&cx).full_offset();
+                let fragment_end = old_fragments.end(&cx).0.full_offset();
                 let mut intersection = fragment.clone();
                 let intersection_end = cmp::min(range.end, fragment_end);
                 if fragment.was_visible(version, &self.undo_map) {
@@ -846,6 +905,15 @@ impl Buffer {
                     intersection.visible = false;
                 }
                 if intersection.len > 0 {
+                    if fragment.visible && !intersection.visible {
+                        let old_start = old_fragments.start().1
+                            + (fragment_start.0 - old_fragments.start().0.full_offset().0);
+                        let new_start = new_fragments.summary().text.visible;
+                        edits.push(Edit {
+                            old: old_start..old_start + intersection.len,
+                            new: new_start..new_start,
+                        });
+                    }
                     new_ropes.push_fragment(&intersection, fragment.visible);
                     new_fragments.push(intersection, &None);
                     fragment_start = intersection_end;
@@ -858,8 +926,8 @@ impl Buffer {
 
         // If the current fragment has been partially consumed, then consume the rest of it
         // and advance to the next fragment before slicing.
-        if fragment_start > old_fragments.start().full_offset() {
-            let fragment_end = old_fragments.end(&cx).full_offset();
+        if fragment_start > old_fragments.start().0.full_offset() {
+            let fragment_end = old_fragments.end(&cx).0.full_offset();
             if fragment_end > fragment_start {
                 let mut suffix = old_fragments.item().unwrap().clone();
                 suffix.len = fragment_end.0 - fragment_start.0;
@@ -880,9 +948,11 @@ impl Buffer {
         self.snapshot.deleted_text = deleted_text;
         self.local_clock.observe(timestamp.local());
         self.lamport_clock.observe(timestamp.lamport());
+        self.update_subscriptions(edits);
     }
 
     fn apply_undo(&mut self, undo: &UndoOperation) -> Result<()> {
+        let mut edits = Patch::default();
         self.snapshot.undo_map.insert(undo);
 
         let mut cx = undo.version.clone();
@@ -891,7 +961,7 @@ impl Buffer {
         }
         let cx = Some(cx);
 
-        let mut old_fragments = self.fragments.cursor::<VersionedFullOffset>();
+        let mut old_fragments = self.fragments.cursor::<(VersionedFullOffset, usize)>();
         let mut new_fragments = old_fragments.slice(
             &VersionedFullOffset::Offset(undo.ranges[0].start),
             Bias::Right,
@@ -902,7 +972,7 @@ impl Buffer {
         new_ropes.push_tree(new_fragments.summary().text);
 
         for range in &undo.ranges {
-            let mut end_offset = old_fragments.end(&cx).full_offset();
+            let mut end_offset = old_fragments.end(&cx).0.full_offset();
 
             if end_offset < range.start {
                 let preceding_fragments = old_fragments.slice(
@@ -925,11 +995,25 @@ impl Buffer {
                         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;
+                    if fragment_was_visible && !fragment.visible {
+                        edits.push(Edit {
+                            old: old_start..old_start + fragment.len,
+                            new: new_start..new_start,
+                        });
+                    } else if !fragment_was_visible && fragment.visible {
+                        edits.push(Edit {
+                            old: old_start..old_start,
+                            new: new_start..new_start + fragment.len,
+                        });
+                    }
                     new_ropes.push_fragment(&fragment, fragment_was_visible);
                     new_fragments.push(fragment, &None);
 
                     old_fragments.next(&cx);
-                    if end_offset == old_fragments.end(&cx).full_offset() {
+                    if end_offset == old_fragments.end(&cx).0.full_offset() {
                         let unseen_fragments = old_fragments.slice(
                             &VersionedFullOffset::Offset(end_offset),
                             Bias::Right,
@@ -938,7 +1022,7 @@ impl Buffer {
                         new_ropes.push_tree(unseen_fragments.summary().text);
                         new_fragments.push_tree(unseen_fragments, &None);
                     }
-                    end_offset = old_fragments.end(&cx).full_offset();
+                    end_offset = old_fragments.end(&cx).0.full_offset();
                 } else {
                     break;
                 }
@@ -954,6 +1038,7 @@ impl Buffer {
         self.snapshot.fragments = new_fragments;
         self.snapshot.visible_text = visible_text;
         self.snapshot.deleted_text = deleted_text;
+        self.update_subscriptions(edits);
         Ok(())
     }
 
@@ -1110,6 +1195,23 @@ impl Buffer {
         })
     }
 
+    pub fn subscribe(&mut self) -> Subscription {
+        let subscription = Subscription(Default::default());
+        self.subscriptions.push(Arc::downgrade(&subscription.0));
+        subscription
+    }
+
+    fn update_subscriptions(&mut self, edits: Patch<usize>) {
+        self.subscriptions.retain(|subscription| {
+            if let Some(subscription) = subscription.upgrade() {
+                subscription.lock().push(edits.clone());
+                true
+            } else {
+                false
+            }
+        });
+    }
+
     pub fn selection_set(&self, set_id: SelectionSetId) -> Result<&SelectionSet> {
         self.selections
             .get(&set_id)