fix: preserve diff semantic highlighting across pane focus

src/editor.rs

@@ -1477,6 +1477,27 @@ impl Editor {
             .map(|_| focus)
     }
 
+    pub(crate) fn diff_semantic_tokens(&self, focus: Focus) -> &[SemanticToken] {
+        let Some(diff) = self.diff.as_ref() else {
+            return &[];
+        };
+        let buffer = if focus == Focus::After && diff.after_editable() {
+            diff.live_buffer
+                .and_then(|id| self.buffer(id))
+                .filter(|buffer| Some(buffer.text_revision) == diff.live_revision)
+        } else {
+            let Some(comparison) = diff.comparison_id else {
+                return &[];
+            };
+            std::iter::once(&self.active)
+                .chain(self.parked.values())
+                .find(|buffer| buffer.diff_snapshot == Some((comparison, diff.file, focus)))
+        };
+        buffer
+            .and_then(|buffer| buffer.semantic_tokens.as_deref())
+            .unwrap_or_default()
+    }
+
     pub(crate) fn mutation_blocked(&self) -> bool {
         self.active.diff_snapshot.is_some() || (self.diff.is_some() && !self.diff_editing())
     }