From 2b699053e67949dd4d12baefef20138c8d9ce4b4 Mon Sep 17 00:00:00 2001
From: Michael Sloan <michael@zed.dev>
Date: Fri, 13 Dec 2024 11:16:30 -0700
Subject: [PATCH] Log invariant violations in fuzzy string match iterator
 (#21983)

Seeing frequent inscrutable panics here

Release Notes:

- N/A
---
 Cargo.lock                  |  1 +
 crates/fuzzy/Cargo.toml     |  1 +
 crates/fuzzy/src/strings.rs | 14 ++++++++++++++
 3 files changed, 16 insertions(+)

diff --git a/Cargo.lock b/Cargo.lock
index c60b84b877ba2b9dd2f8ba60f9e75356995c16b7..86bb0fc743927663d2e7216058bf22581cc981f4 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -5030,6 +5030,7 @@ name = "fuzzy"
 version = "0.1.0"
 dependencies = [
  "gpui",
+ "log",
  "util",
 ]
 
diff --git a/crates/fuzzy/Cargo.toml b/crates/fuzzy/Cargo.toml
index e3a016c98b718cc9852b9abece47213c284f8fcb..6d115fb1b5be8bdf5fdd9e4e9059ec49c8ba58b7 100644
--- a/crates/fuzzy/Cargo.toml
+++ b/crates/fuzzy/Cargo.toml
@@ -15,3 +15,4 @@ doctest = false
 [dependencies]
 gpui.workspace = true
 util.workspace = true
+log.workspace = true
diff --git a/crates/fuzzy/src/strings.rs b/crates/fuzzy/src/strings.rs
index e1f6de37a572b3f6c7f0f676f8ad5dda7ba53498..1a5fb2b02f89147110f29e47584281ad150419b5 100644
--- a/crates/fuzzy/src/strings.rs
+++ b/crates/fuzzy/src/strings.rs
@@ -61,9 +61,23 @@ impl StringMatch {
         let mut positions = self.positions.iter().peekable();
         iter::from_fn(move || {
             if let Some(start) = positions.next().copied() {
+                if start >= self.string.len() {
+                    log::error!(
+                        "Invariant violation: Index {start} out of range in string {:?}",
+                        self.string
+                    );
+                    return None;
+                }
                 let mut end = start + self.char_len_at_index(start);
                 while let Some(next_start) = positions.peek() {
                     if end == **next_start {
+                        if end >= self.string.len() {
+                            log::error!(
+                                "Invariant violation: Index {end} out of range in string {:?}",
+                                self.string
+                            );
+                            return None;
+                        }
                         end += self.char_len_at_index(end);
                         positions.next();
                     } else {