fix: diff_content renders overlapping diff lines

src/util/diff.rs

@@ -1,4 +1,4 @@
-use std::sync::Arc;
+use std::{ops::Deref, sync::Arc};
 
 use similar::DiffableStr;
 
@@ -145,13 +145,23 @@ pub(crate) fn diff_content(
             new_len,
         } => {
             for i in 0..new_len.max(old_len) {
-                let old_line = old_index + i;
-                let new_line = new_index + i;
+                let old_line = if i < old_len {
+                    Some(old_index + i)
+                } else {
+                    None
+                };
+                let new_line = if i < new_len {
+                    Some(new_index + i)
+                } else {
+                    None
+                };
                 let diff_line_i = DiffLineIndex(diff_lines.len());
 
-                let diff_line = match (old_line_ranges.get(old_line), new_line_ranges.get(new_line))
-                {
-                | (Some(old_range), Some(new_range)) => {
+                let diff_line = match (
+                    old_line.and_then(|i| old_line_ranges.get(i).map(|it| (i, it))),
+                    new_line.and_then(|i| new_line_ranges.get(i).map(|it| (i, it))),
+                ) {
+                | (Some((old_line, old_range)), Some((new_line, new_range))) => {
                     push_diff_line_index(old_line, diff_line_i, &mut old_line_to_diff_line_indices);
                     push_diff_line_index(new_line, diff_line_i, &mut new_line_to_diff_line_indices);
 
@@ -170,7 +180,7 @@ pub(crate) fn diff_content(
                     }
                 }
 
-                | (None, Some(new_range)) => {
+                | (None, Some((new_line, new_range))) => {
                     push_diff_line_index(new_line, diff_line_i, &mut new_line_to_diff_line_indices);
 
                     DiffLine {
@@ -186,7 +196,7 @@ pub(crate) fn diff_content(
                     }
                 }
 
-                | (Some(old_range), None) => {
+                | (Some((old_line, old_range)), None) => {
                     push_diff_line_index(old_line, diff_line_i, &mut old_line_to_diff_line_indices);
 
                     DiffLine {
@@ -271,3 +281,9 @@ impl ContentDiff {
         }
     }
 }
+
+impl Into<usize> for DiffLineIndex {
+    fn into(self) -> usize {
+        self.0
+    }
+}