A regular expression search comes back: costly patterns refused, long lines windowed, 300 ms deadline

mvzr backtracks with no bound on its work (a*a*a*a*x over a hundred a's takes a
second, each repeat multiplying by the haystack length), and a search runs holding
the editor's turn, so one pasted pattern froze the editor. pardes does not write or
vendor a regex engine, so regexp.zig bounds what it hands mvzr: more than four
repeats is refused, a line longer than a window sized from measured worst cases is
searched in half-overlapping windows, and a deadline stops the search. addr names
each failure; normal s/S keeps what it found. The prescan also stops reading an
escaped backslash before n as a newline, and ends a class where mvzr does.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 3 insertions, 2 deletions

diff --git a/src/normal.zig b/src/normal.zig
index 8c5f232d..09e06b13 100644
--- a/src/normal.zig
+++ b/src/normal.zig
@@ -110,7 +110,8 @@ pub fn applySelRegex(p: *Pardes, pane: *Pane, t: *Text, pat: []const u8, split:
             var at = from;
             var piece = from; // split: where the next piece begins
             while (at < to and m < Text.max_selections) {
-                const hit_at = re.find(hay_all, at, to, to) orelse break;
+                // A search too slow to finish keeps what it found so far.
+                const hit_at = (re.find(hay_all, at, to, to) catch break) orelse break;
                 if (split) {
                     out[m] = .{ .anchor = piece, .head = hit_at.start };
                     m += 1;
@@ -127,7 +128,7 @@ pub fn applySelRegex(p: *Pardes, pane: *Pane, t: *Text, pat: []const u8, split:
                 m += 1;
             }
         }
-    }
+    } else |_| {}
     if (m == 0) {
         // the text CAN move under an armed prompt (a tag chord runs a
         // builtin), and these are raw offsets into the surface as it was