Panic when reloading a file that has shrunk

[paholg]

Summary

If you reload a file while your cursor is out-of-bounds of the reloaded file, a panic occurs.

Backtrace:

thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Line index out of bounds: line index 4569, Rope/RopeSlice line count 2923', /build/helix-22.03-vendor.tar.gz/ropey/src/slice.rs:424:41
stack backtrace:
   0: rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::result::unwrap_failed
   3: ropey::slice::RopeSlice::line_to_byte
   4: helix_term::ui::editor::EditorView::doc_syntax_highlights
   5: helix_term::ui::editor::EditorView::render_view
   6: <helix_term::ui::editor::EditorView as helix_term::compositor::Component>::render
   7: helix_term::compositor::Compositor::render
   8: helix_term::application::Application::handle_terminal_events
   9: helix_term::application::Application::event_loop::{{closure}}
  10: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
  11: tokio::park::thread::CachedParkThread::block_on
  12: tokio::runtime::thread_pool::ThreadPool::block_on
  13: tokio::runtime::Runtime::block_on
  14: hx::main
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

Reproduction Steps

1. Open a file and go to line N (N must be at least some number. It works for me at ~200).
2. Externally edit the file so that it is much shorter than N
3. :reload the file.

Helix log

There is no relevant log information.

Platform

Linux

Terminal Emulator

gnome-terminal

Helix Version

helix 22.03 (d4e45fd)

[pppKin]

Can reproduce. ensure_cursor_in_view after a reload seems necessary.

Something like this would solve the issue.

doc.reload(view.id).and_then(|_| {
    view.ensure_cursor_in_view(doc, 0);
    Ok(())
})

What this look like, in case anyone is just wondering and don't want to cargo run, is to bring the end of the file to top of the editor view.
I think for better user experience we might want to scroll back a bit further. What do you guys think?

[Johan-Mi]

Issue still reproduces with :reflow, for example when reflowing the entire contents of a file consisting of ~40 single-character lines.

[archseer]

Yeah, reflow is a separate command that needs a similar fix.