vercel · anthonyshew · Jul 5, 2025
@@ -862,12 +862,9 @@ impl Grid {
             let scrolled = self.row_inc_scroll(1);
             prev_pos.row -= scrolled;
             let new_pos = self.pos;
-            self.drawing_row_mut(prev_pos.row)
-                // we assume self.pos.row is always valid, and so prev_pos.row
-                // must be valid because it is always less than or equal to
-                // self.pos.row
-                .unwrap()
-                .wrap(wrap && prev_pos.row + 1 == new_pos.row);
+            if let Some(row) = self.drawing_row_mut(prev_pos.row) {
+                row.wrap(wrap && prev_pos.row + 1 == new_pos.row);
+            }
         }
     }
 

@@ -0,0 +1,50 @@
+use turborepo_vt100 as vt100;
+
+#[test]
+fn col_wrap_with_invalid_row_does_not_panic() {
+    // This test verifies that col_wrap handles the case where drawing_row_mut
+    // returns None gracefully, without panicking.
+
+    let mut parser = vt100::Parser::new(24, 80, 0);
+
+    // Create a scenario where we have a very small terminal
+    parser.screen_mut().set_size(2, 5);
+
+    // Fill the screen to trigger scrolling
+    parser.process(b"12345"); // Fill first row
+    parser.process(b"67890"); // This should wrap and trigger col_wrap
+    parser.process(b"abcde"); // This should cause more scrolling
+    parser.process(b"fghij"); // And more scrolling
+
+    // At this point, we should have scrolled enough that some row references
+    // in col_wrap might be invalid. The key is that this should not panic.
+
+    // Try to trigger more wrapping with a wide character that might cause
+    // the edge case where prev_pos.row is out of bounds
+    parser.process(b"klmno");
+    parser.process(b"pqrst");
+
+    // If we get here without panicking, the fix is working
+    assert_eq!(parser.screen().size(), (2, 5));
+}
+
+#[test]
+fn col_wrap_edge_case_with_scrolling() {
+    // Another test to specifically target the edge case in col_wrap
+    let mut parser = vt100::Parser::new(3, 10, 0);
+
+    // Fill multiple lines to cause scrolling
+    for i in 0..10 {
+        let line = format!("line{:06}", i);
+        parser.process(line.as_bytes());
+        parser.process(b"\r\n");
+    }
+
+    // Now try to trigger col_wrap with a scenario that might cause
+    // drawing_row_mut to return None
+    parser.process(b"1234567890"); // Exactly fill the width
+    parser.process(b"X"); // This should trigger col_wrap
+
+    // The test passes if we don't panic
+    assert!(parser.screen().contents().contains("X"));
+}