editor: Fix panic when editor::SelectLargerSyntaxNode overflows excerpt in multi buffer (#25585)

Closes #25513

This PR handles case when `editor::SelectLargerSyntaxNode` expands
across excerpt boundaries and eventually crashes in multi buffer.

Release Notes:

- Fixed panic caused when `editor::SelectLargerSyntaxNode` is called
repetedly in multi buffer.

Co-authored-by: Ben Kunkle <ben.kunkle@gmail.com>

crates/editor/src/editor.rs

@@ -132,7 +132,7 @@ pub use multi_buffer::{
 };
 use multi_buffer::{
     ExcerptInfo, ExpandExcerptDirection, MultiBufferDiffHunk, MultiBufferPoint, MultiBufferRow,
-    ToOffsetUtf16,
+    MultiOrSingleBufferOffsetRange, ToOffsetUtf16,
 };
 use project::{
     lsp_store::{CompletionDocumentation, FormatTrigger, LspFormatTarget, OpenLspBufferHandle},
@@ -10738,7 +10738,10 @@ impl Editor {
                 while let Some((node, containing_range)) = buffer.syntax_ancestor(new_range.clone())
                 {
                     new_node = Some(node);
-                    new_range = containing_range;
+                    new_range = match containing_range {
+                        MultiOrSingleBufferOffsetRange::Single(_) => break,
+                        MultiOrSingleBufferOffsetRange::Multi(range) => range,
+                    };
                     if !display_map.intersects_fold(new_range.start)
                         && !display_map.intersects_fold(new_range.end)
                     {

crates/editor/src/hover_popover.rs

@@ -15,7 +15,7 @@ use itertools::Itertools;
 use language::{DiagnosticEntry, Language, LanguageRegistry};
 use lsp::DiagnosticSeverity;
 use markdown::{Markdown, MarkdownStyle};
-use multi_buffer::ToOffset;
+use multi_buffer::{MultiOrSingleBufferOffsetRange, ToOffset};
 use project::{HoverBlock, HoverBlockKind, InlayHintLabelPart};
 use settings::Settings;
 use std::{borrow::Cow, cell::RefCell};
@@ -447,11 +447,13 @@ fn show_hover(
                     })
                     .or_else(|| {
                         let snapshot = &snapshot.buffer_snapshot;
-                        let offset_range = snapshot.syntax_ancestor(anchor..anchor)?.1;
+                        match snapshot.syntax_ancestor(anchor..anchor)?.1 {
-                        Some(
+                            MultiOrSingleBufferOffsetRange::Multi(range) => Some(
-                            snapshot.anchor_before(offset_range.start)
+                                snapshot.anchor_before(range.start)
-                                ..snapshot.anchor_after(offset_range.end),
+                                    ..snapshot.anchor_after(range.end),
-                        )
+                            ),
+                            MultiOrSingleBufferOffsetRange::Single(_) => None,
+                        }
                     })
                     .unwrap_or_else(|| anchor..anchor);
 

crates/multi_buffer/src/multi_buffer.rs

@@ -78,6 +78,12 @@ pub struct MultiBuffer {
     capability: Capability,
 }
 
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum MultiOrSingleBufferOffsetRange {
+    Single(Range<usize>),
+    Multi(Range<usize>),
+}
+
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub enum Event {
     ExcerptsAdded {
@@ -5682,13 +5688,19 @@ impl MultiBufferSnapshot {
     pub fn syntax_ancestor<T: ToOffset>(
         &self,
         range: Range<T>,
-    ) -> Option<(tree_sitter::Node, Range<usize>)> {
+    ) -> Option<(tree_sitter::Node, MultiOrSingleBufferOffsetRange)> {
         let range = range.start.to_offset(self)..range.end.to_offset(self);
         let mut excerpt = self.excerpt_containing(range.clone())?;
         let node = excerpt
             .buffer()
             .syntax_ancestor(excerpt.map_range_to_buffer(range))?;
-        Some((node, excerpt.map_range_from_buffer(node.byte_range())))
+        let node_range = node.byte_range();
+        let range = if excerpt.contains_buffer_range(node_range.clone()) {
+            MultiOrSingleBufferOffsetRange::Multi(excerpt.map_range_from_buffer(node_range))
+        } else {
+            MultiOrSingleBufferOffsetRange::Single(node_range)
+        };
+        Some((node, range))
     }
 
     pub fn outline(&self, theme: Option<&SyntaxTheme>) -> Option<Outline<Anchor>> {
@@ -6660,9 +6672,17 @@ impl<'a> MultiBufferExcerpt<'a> {
 
     /// Map a range within the [`Buffer`] to a range within the [`MultiBuffer`]
     pub fn map_range_from_buffer(&mut self, buffer_range: Range<usize>) -> Range<usize> {
+        if buffer_range.start < self.buffer_offset {
+            log::warn!("Attempting to map a range from a buffer offset that starts before the current buffer offset");
+            return buffer_range;
+        }
         let overshoot = buffer_range.start - self.buffer_offset;
         let excerpt_offset = ExcerptDimension(self.excerpt_offset.0 + overshoot);
         self.diff_transforms.seek(&excerpt_offset, Bias::Right, &());
+        if excerpt_offset.0 < self.diff_transforms.start().1 .0 {
+            log::warn!("Attempting to map a range from a buffer offset that starts before the current buffer offset");
+            return buffer_range;
+        }
         let overshoot = excerpt_offset.0 - self.diff_transforms.start().1 .0;
         let start = self.diff_transforms.start().0 .0 + overshoot;