LSP: index out of bounds: the len is 1 but the index is 1

[dmorn]

Summary

Erlang project with elp. helix randomly panics!

Trace:

thread 'main' panicked at helix-term/src/ui/lsp.rs:163:35:
index out of bounds: the len is 1 but the index is 1
stack backtrace:
   0:        0x1019ce458 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h4bff038afc05d0ab
   1:        0x100df7698 - core::fmt::write::he9fa43146d420946
   2:        0x1019ca2d8 - std::io::Write::write_fmt::hf4fd30c8192b15d9
   3:        0x1019ce298 - std::sys_common::backtrace::print::h5d71f7b09493fc9b
   4:        0x1019cfe68 - std::panicking::default_hook::{{closure}}::hb75620628e95e648
   5:        0x1019cfbac - std::panicking::default_hook::h4ac4acc64d21c4ad
   6:        0x1019d045c - std::panicking::rust_panic_with_hook::h81dc715fa5de32cf
   7:        0x1019d0234 - std::panicking::begin_panic_handler::{{closure}}::h26c73eb75670321f
   8:        0x1019ce8ac - std::sys_common::backtrace::__rust_end_short_backtrace::hef4773cf0f80485b
   9:        0x1019cffe8 - _rust_begin_unwind
  10:        0x101a92620 - core::panicking::panic_fmt::h10bd3bfe5bb30d67
  11:        0x101a92764 - core::panicking::panic_bounds_check::h0059132d60d26813
  12:        0x1013e68d4 - <helix_term::ui::lsp::SignatureHelp as helix_term::compositor::Component>::required_size::hcedf4e7ddb24c3d7
  13:        0x10153578c - helix_term::ui::popup::Popup<T>::render_info::h3d72aeab9a0803cc
  14:        0x1015380f4 - <helix_term::ui::popup::Popup<T> as helix_term::compositor::Component>::render::h9b998179b28c9188
  15:        0x10178b498 - helix_term::application::Application::render::{{closure}}::hd9cb597a36e0ecf8
  16:        0x10178963c - helix_term::application::Application::run::{{closure}}::h7c093398c458d3a0
  17:        0x10179b47c - tokio::runtime::park::CachedParkThread::block_on::h2a5eb8c2a2745328
  18:        0x101804688 - hx::main::h40afa6c5c39a856d
  19:        0x1017f4984 - std::sys_common::backtrace::__rust_begin_short_backtrace::hf2c8060bb84d5bac
  20:        0x1017f8e34 - std::rt::lang_start::{{closure}}::h6934599efcb3bcb2
  21:        0x1019c3b38 - std::rt::lang_start_internal::haeade8bb0e866fa6
  22:        0x101804c84 - _main

Reproduction Steps

I tried this:

1. hx
2. Coding

I expected this to happen:
Helix keeps on working.

Instead, this happened:
Helix panics!

Helix log

~/.cache/helix/helix.log

2024-07-22T10:20:50.108 helix_term::application [WARN] unhandled window/showMessage: ShowMessageParams { typ: Info, message: "ELP version: 1.1.0+build-2024-07-16" }
2024-07-22T10:20:51.262 helix_term::application [ERROR] Language Server: Method workspace/codeLens/refresh not found in request 3
2024-07-22T11:02:59.314 helix_term::application [WARN] unhandled window/showMessage: ShowMessageParams { typ: Info, message: "ELP version: 1.1.0+build-2024-07-16" }
2024-07-22T11:02:59.331 helix_lsp [ERROR] client was already removed
2024-07-22T11:02:59.335 helix_lsp::transport [ERROR] elp err: <- StreamClosed
2024-07-22T11:03:00.366 helix_term::application [ERROR] Language Server: Method workspace/codeLens/refresh not found in request 3
2024-07-22T11:15:23.245 helix_term::application [WARN] unhandled window/showMessage: ShowMessageParams { typ: Info, message: "ELP version: 1.1.0+build-2024-07-16" }
2024-07-22T11:15:24.374 helix_term::application [ERROR] Language Server: Method workspace/codeLens/refresh not found in request 3
2024-07-22T11:19:38.839 helix_term::application [WARN] unhandled window/showMessage: ShowMessageParams { typ: Info, message: "ELP version: 1.1.0+build-2024-07-16" }
2024-07-22T11:19:39.864 helix_term::application [ERROR] Language Server: Method workspace/codeLens/refresh not found in request 3
2024-07-22T11:20:38.191 helix_term::application [WARN] unhandled window/showMessage: ShowMessageParams { typ: Info, message: "ELP version: 1.1.0+build-2024-07-16" }
2024-07-22T11:20:39.034 helix_term::application [ERROR] Language Server: Method workspace/codeLens/refresh not found in request 3

Platform

macOS

Terminal Emulator

iTerm2

Installation Method

source

Helix Version

helix 24.7 (dbaa636)

[the-mikedavis]

The backtrace comes from the signature help component: the popup that shows the spec of the function you're typing out and which parameter you're on. ELP is sending an active_signature of 1 even though there is only one signature (0-indexed). We need to be more defensive and as the spec says:

If omitted or the value lies outside the range of signatures the value defaults to zero or is ignore[d] if the SignatureHelp as no signatures

But if you have an easy reproduction case you should report this to ELP as well - this is the only instance of a language server sending an out-of-bound index I've seen so far. The spec does allow it but I suspect it may be a bug in ELP anyways.