editor: Fix utf8 boundary panic in `process_completion_for_edit` (#39561)

Lukas Wirth created 1 month ago

Fixes ZED-1WH

Release Notes:

- Fixed panic when requesting completions after a multibyte character

Change summary

crates/editor/src/editor.rs | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)

Detailed changes

crates/editor/src/editor.rs

@@ -185,7 +185,7 @@ use std::{
     time::{Duration, Instant},
 };
 use task::{ResolvedTask, RunnableTag, TaskTemplate, TaskVariables};
-use text::{BufferId, FromAnchor, OffsetUtf16, Rope};
+use text::{BufferId, FromAnchor, OffsetUtf16, Rope, ToOffset as _};
 use theme::{
     ActiveTheme, PlayerColor, StatusColors, SyntaxTheme, Theme, ThemeSettings,
     observe_buffer_font_size_adjustment,
@@ -10459,10 +10459,10 @@ impl Editor {
             }
 
             let buffer = display_map.buffer_snapshot();
-            let mut edit_start = Point::new(rows.start.0, 0).to_offset(buffer);
+            let mut edit_start = ToOffset::to_offset(&Point::new(rows.start.0, 0), buffer);
             let edit_end = if buffer.max_point().row >= rows.end.0 {
                 // If there's a line after the range, delete the \n from the end of the row range
-                Point::new(rows.end.0, 0).to_offset(buffer)
+                ToOffset::to_offset(&Point::new(rows.end.0, 0), buffer)
             } else {
                 // If there isn't a line after the range, delete the \n from the line before the
                 // start of the row range
@@ -12263,7 +12263,7 @@ impl Editor {
             }
 
             let start = Point::new(start_row, 0);
-            let start_offset = start.to_offset(&buffer);
+            let start_offset = ToOffset::to_offset(&start, &buffer);
             let end = Point::new(end_row, buffer.line_len(MultiBufferRow(end_row)));
             let selection_text = buffer.text_for_range(start..end).collect::<String>();
             let mut first_line_delimiter = None;
@@ -21930,12 +21930,16 @@ fn process_completion_for_edit(
     let buffer = buffer.read(cx);
     let buffer_snapshot = buffer.snapshot();
     let (snippet, new_text) = if completion.is_snippet() {
+        let mut snippet_source = completion.new_text.clone();
         // Workaround for typescript language server issues so that methods don't expand within
         // strings and functions with type expressions. The previous point is used because the query
         // for function identifier doesn't match when the cursor is immediately after. See PR #30312
-        let mut snippet_source = completion.new_text.clone();
-        let mut previous_point = text::ToPoint::to_point(cursor_position, buffer);
-        previous_point.column = previous_point.column.saturating_sub(1);
+        let previous_point = text::ToPoint::to_point(cursor_position, &buffer_snapshot);
+        let previous_point = if previous_point.column > 0 {
+            cursor_position.to_previous_offset(&buffer_snapshot)
+        } else {
+            cursor_position.to_offset(&buffer_snapshot)
+        };
         if let Some(scope) = buffer_snapshot.language_scope_at(previous_point)
             && scope.prefers_label_for_snippet_in_completion()
             && let Some(label) = completion.label()