Fix Global::gt and rename it to changed_since

A false negative return value of `gt` was preventing guests' multibuffers from
syncing correctly.

Co-Authored-By: Nathan Sobo <nathan@zed.dev>

crates/clock/src/clock.rs

@@ -178,7 +178,7 @@ impl Global {
         }
     }
 
-    pub fn ge(&self, other: &Self) -> bool {
+    pub fn observed_all(&self, other: &Self) -> bool {
         let mut lhs = self.0.iter();
         let mut rhs = other.0.iter();
         loop {
@@ -196,22 +196,16 @@ impl Global {
         }
     }
 
-    pub fn gt(&self, other: &Self) -> bool {
-        let mut lhs = self.0.iter();
-        let mut rhs = other.0.iter();
-        loop {
-            if let Some(left) = lhs.next() {
-                if let Some(right) = rhs.next() {
-                    if left <= right {
-                        return false;
-                    }
-                } else {
-                    return true;
-                }
-            } else {
-                return rhs.next().is_none();
+    pub fn changed_since(&self, other: &Self) -> bool {
+        if self.0.len() > other.0.len() {
+            return true;
+        }
+        for (left, right) in self.0.iter().zip(other.0.iter()) {
+            if left > right {
+                return true;
             }
         }
+        false
     }
 
     pub fn iter<'a>(&'a self) -> impl 'a + Iterator<Item = Local> {

crates/editor/src/multi_buffer.rs

@@ -804,7 +804,7 @@ impl MultiBuffer {
             let selections_update_count = buffer.selections_update_count();
             let diagnostics_update_count = buffer.diagnostics_update_count();
 
-            let buffer_edited = version.gt(&buffer_state.last_version);
+            let buffer_edited = version.changed_since(&buffer_state.last_version);
             let buffer_reparsed = parse_count > buffer_state.last_parse_count;
             let buffer_selections_updated =
                 selections_update_count > buffer_state.last_selections_update_count;
@@ -2116,6 +2116,26 @@ mod tests {
         );
     }
 
+    #[gpui::test]
+    fn test_remote_multibuffer(cx: &mut MutableAppContext) {
+        let host_buffer = cx.add_model(|cx| Buffer::new(0, "a", cx));
+        let guest_buffer = cx.add_model(|cx| {
+            let message = host_buffer.read(cx).to_proto();
+            Buffer::from_proto(1, message, None, cx).unwrap()
+        });
+        let multibuffer = cx.add_model(|cx| MultiBuffer::singleton(guest_buffer.clone(), cx));
+        let snapshot = multibuffer.read(cx).snapshot(cx);
+        assert_eq!(snapshot.text(), "a");
+
+        guest_buffer.update(cx, |buffer, cx| buffer.edit([1..1], "b", cx));
+        let snapshot = multibuffer.read(cx).snapshot(cx);
+        assert_eq!(snapshot.text(), "ab");
+
+        guest_buffer.update(cx, |buffer, cx| buffer.edit([2..2], "c", cx));
+        let snapshot = multibuffer.read(cx).snapshot(cx);
+        assert_eq!(snapshot.text(), "abc");
+    }
+
     #[gpui::test]
     fn test_excerpt_buffer(cx: &mut MutableAppContext) {
         let buffer_1 = cx.add_model(|cx| Buffer::new(0, sample_text(6, 6, 'a'), cx));

crates/language/src/buffer.rs

@@ -725,7 +725,8 @@ impl Buffer {
                             let grammar_changed = this
                                 .grammar()
                                 .map_or(true, |curr_grammar| !Arc::ptr_eq(&grammar, curr_grammar));
-                            let parse_again = this.version.gt(&parsed_version) || grammar_changed;
+                            let parse_again =
+                                this.version.changed_since(&parsed_version) || grammar_changed;
                             this.parsing_in_background = false;
                             this.did_finish_parsing(new_tree, parsed_version, cx);
 
@@ -1095,12 +1096,12 @@ impl Buffer {
     }
 
     pub fn is_dirty(&self) -> bool {
-        !self.saved_version.ge(&self.version)
+        !self.saved_version.observed_all(&self.version)
             || self.file.as_ref().map_or(false, |file| file.is_deleted())
     }
 
     pub fn has_conflict(&self) -> bool {
-        !self.saved_version.ge(&self.version)
+        !self.saved_version.observed_all(&self.version)
             && self
                 .file
                 .as_ref()

crates/text/src/text.rs

@@ -1125,8 +1125,8 @@ impl Buffer {
             false
         } else {
             match op {
-                Operation::Edit(edit) => self.version.ge(&edit.version),
-                Operation::Undo { undo, .. } => self.version.ge(&undo.version),
+                Operation::Edit(edit) => self.version.observed_all(&edit.version),
+                Operation::Undo { undo, .. } => self.version.observed_all(&undo.version),
             }
         }
     }
@@ -1648,10 +1648,10 @@ impl BufferSnapshot {
         let fragments_cursor = if *since == self.version {
             None
         } else {
-            Some(
-                self.fragments
-                    .filter(move |summary| !since.ge(&summary.max_version), &None),
-            )
+            Some(self.fragments.filter(
+                move |summary| !since.observed_all(&summary.max_version),
+                &None,
+            ))
         };
         let mut cursor = self
             .fragments
@@ -2025,7 +2025,7 @@ impl<'a> sum_tree::Dimension<'a, FragmentSummary> for VersionedFullOffset {
     fn add_summary(&mut self, summary: &'a FragmentSummary, cx: &Option<clock::Global>) {
         if let Self::Offset(offset) = self {
             let version = cx.as_ref().unwrap();
-            if version.ge(&summary.max_insertion_version) {
+            if version.observed_all(&summary.max_insertion_version) {
                 *offset += summary.text.visible + summary.text.deleted;
             } else if version.observed_any(&summary.min_insertion_version) {
                 *self = Self::Invalid;