panic: Char index out of bounds

[alistaircarscadden]

Summary

thread 'main' panicked at C:\Users\runneradmin/.cargo\registry\src\index.crates.io-6f17d22bba15001f\ropey-1.6.1\src\slice.rs:360:41:
called `Result::unwrap()` on an `Err` value: Char index out of bounds: char index 88087, Rope/RopeSlice char length 10230

Reproduction Steps

I tried this:

Panic occurred during selection over many lines. I clicked and dragged with mouse across about 20 lines and was intending to press "s" to select a specific word. I do not know if I had already clicked s or not when the panic happened.

I expected this to happen:

No panic

Instead, this happened:

Panic

Helix log

Dunno where this file is on Windows, no such ~/.cache dir

Platform

Windows

Terminal Emulator

alacritty 0.15.1 (0c405d5)

Installation Method

scoop

Helix Version

helix 25.01.1 (e7ac2fcd)

[lupuszr]

I observed the same issue on osx, the logs contain nothing. I will try to run it with RUST_BACKTRACE=full and add more detail if I manage to reproduce it.

[RoloEdits]

I tried to replicate this but couldn't seem to trigger it myself. I am based on the latest master commit. If you can reliably reproduce, if possible, try out the latest master to see if it still happens.

[lupuszr]

Its not reliable, what I observed it was failing when editing large files with 3-4k lines. I will try with master

[alistaircarscadden]

I just had it again on a 1-2KB file. Sorry but I don't know how to be more useful with reproducing it.

thread 'main' panicked at C:\Users\runneradmin/.cargo\registry\src\index.crates.io-6f17d22bba15001f\ropey-1.6.1\src\slice.rs:360:41:
called `Result::unwrap()` on an `Err` value: Char index out of bounds: char index 5473, Rope/RopeSlice char length 389
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[RoloEdits]

I think that might be #12626 which looks like it was fixed in 25.01.1 4bd17e542ef4b6103b7b5821418c02fe3ab2ad62. What version are you running @alistaircarscadden ?

[alistaircarscadden]

@RoloEdits helix 25.01.1 (e7ac2fcd)

[nim65s]

Also got this on NixOS, helix 25.01.1 (e7ac2fcd):

thread 'main' panicked at /build/helix-25.01.1-vendor/ropey-1.6.1/src/slice.rs:360:41:
called `Result::unwrap()` on an `Err` value: Char index out of bounds: char index 8290, Rope/RopeSlice char length 8289
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[RoloEdits]

If you are able to build from source, from at least 4bd17e542ef4b6103b7b5821418c02fe3ab2ad62, hopefully that has fixed the issue.

[georgesmith46]

I am able to replicate this error on v25.01.1 by doing the following:

1. Open helix and add three lines to the scratch file
2. Open a new scratch file
3. Split the window (horizontally or vertically)
4. Go back to the original window and switch to the original scratch file
5. Go to line 3 and press s
6. Click in the other window with the single line scratch file and press escape

I'm guessing this isn't the only way to replicate the issue though

[kkonevets]

Confirm, I got same error right now

thread 'main' panicked at /home/devel/.cargo/registry/src/index.crates.io-6f17d22bba15001f/ropey-1.6.1/src/slice.rs:360:41:
called `Result::unwrap()` on an `Err` value: Char index out of bounds: char index 15471, Rope/RopeSlice char length 5070
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace 

[clample]

I checked with main and the error still happens, but the exact error message changed a bit. Also added RUST_BACKTRACE=1 - backtrace.txt.

I think that the error comes from that it's possible to switch windows while performing the selection. It seems like this is only possible when clicking with the mouse. If I try to switch windows using keyboard shortcuts - Ctrl-w Right ,jump_view_right - then it isn't possible to switch windows without first aborting the selection, and the error doesn't happen.

Seems related to https://github.com/helix-editor/helix/issues/5632

[slugbyte]

I'm using 25.07.1 and have encountered the same thing about every few days.

For some reason I could not get the link to the backtrace.txt provided by @clample to work so I decided to share one here in case its helpful.

thread 'main' panicked at /home/slugbyte/.cargo/registry/src/index.crates.io-6f17d22bba15001f/ropey-1.6.1/src/slice.rs:360:41:
called `Result::unwrap()` on an `Err` value: Char index out of bounds: char index 3753, Rope/RopeSlice char length 1528
stack backtrace:
   0: rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::result::unwrap_failed
   3: helix_core::graphemes::nth_prev_grapheme_boundary
   4: helix_core::selection::Range::grapheme_aligned
   5: helix_core::selection::Selection::ensure_invariants
   6: helix_view::document::Document::set_selection
   7: helix_term::ui::raw_regex_prompt::{{closure}}
   8: <helix_term::ui::prompt::Prompt as helix_term::compositor::Component>::handle_event
   9: helix_term::compositor::Compositor::handle_event
  10: hx::main_impl::{{closure}}
  11: tokio::runtime::park::CachedParkThread::block_on
  12: tokio::runtime::context::runtime::enter_runtime
  13: tokio::runtime::runtime::Runtime::block_on
  14: hx::main
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

I just set my RUST_BACKTRACE=full and will update ^above if I get something new

[RoloEdits]

@slugbyte Are you able to provide some context of what you were doing when it happened? Are you on linux or mac? Did you have splits? Did you click with a mouse? Did you edit the file externally?

[slugbyte]

@RoloEdits sorry I can't remember too many details... I will add more context if it happens again. I probably had a split open though, I usually have a horizontal split open. All I'm sure of is that I was editing a zig file and I have the zig lsp installed and working with helix, but I'm not sure if that is relevant. I didn't intentinoally edit the file externally (but the lsp might have). I was not using a mouse.

Im on Linux (Fedora 42 x86_64), using ghostty terminal emulator.

[kkonevets]

Same error for me too

$ hx src/some_file.cpp
thread 'main' panicked at /home/devel/.cargo/registry/src/index.crates.io-6f17d22bba15001f/ropey-1.6.1/src/slice.rs:360:41:
called `Result::unwrap()` on an `Err` value: Char index out of bounds: char index 16196, Rope/RopeSlice char length 7335
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Can't reproduce, happened unexpectedly while I pressed g-d, not 100% sure.

UPD: just noticed that I already reported here earlier, sorry guys, looks like it's a frequent bug :)

[markstos]

I ran into this today with 25.07.1 while editing some small files. I'm not sure what the exact trigger was.