ark: investigate panic when updating internal document state

[kevinushey]

I saw this when editing near the end of the document, but haven't been able to reliably reproduce.

thread '<unnamed>' panicked at 'called `Result::unwrap()` on an `Err` value: Char range out of bounds: char range 83..110, Rope/RopeSlice char length 97', /Users/kevin/.cargo/registry/src/github.com-1ecc6299db9ec823/ropey-1.6.0/src/rope.rs:546:37

stack backtrace:

   0: rust_begin_unwind
             at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/panicking.rs:575:5

   1: core::panicking::panic_fmt
             at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/core/src/panicking.rs:64:14
   2: core::result::unwrap_failed
             at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/core/src/result.rs:1790:5

   3: core::result::Result<T,
E>::unwrap
             at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/core/src/result.rs:1112:23

   4: ropey::rope::Rope::remove
             at 
./.cargo/registry/src/github.com-1ecc6299db9ec823/ropey-1.6.0/src/rope.rs:546:9


   5: ark::lsp::documents::Document::update
             at ./positron/extensions/positron-r/amalthea/crates/ark/src/lsp/documents.rs:128:9

   6: <ark::lsp::backend::Backend as tower_lsp::LanguageServer>::did_change::{{closure}}
             at ./positron/extensions/positron-r/amalthea/crates/ark/src/lsp/backend.rs:284:33

   7: <core::pin::Pin<P> as core::future::future::Future>::poll
             at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/core/src/future/future.rs:125:9


   8: tower_lsp::generated::register_lsp_methods::did_change::
{{closure
}}
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/tower-lsp-0.19.0/src/lib.rs:112:1

   9: tower_lsp::jsonrpc::router::Router<S,E>::method::{{closure}}::{{closure}}::{{closure}
}
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/tower-lsp-0.19.0/src/jsonrpc/router.rs:58:63
  10: <core::pin::Pin<P> as core::future::future::Future>::poll
             at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/core/src/future/future.rs:125:9

  11: <futures_util::future::future::map
::Map<Fut,F> 
as core::
future::future::Future
>::poll

             at ./
.cargo/registry/src/github.com-1ecc6299db9ec823/futures-util-0.3.26/src/future/future/map.rs:55:
37

  12: <futures_util::future::future::Map<Fut,F>
 as core::future::
future::Future>::poll
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/futures-util-0.3.26/src/lib.rs:91:
13
  13: <core::pin::Pin<P> as core::future::future::Future>::poll
             at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/core/src/future/future.rs:125:9
  14: <core::pin::Pin<P> as core::future::future::Future>::poll
             at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/core/src/future/future.rs:125:9
  15: <core::pin::Pin<P> as core::future::future::Future>::poll
             at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/core/src/future/future.rs:125:9
  16: <tower_lsp::service::LspService<S> as tower_service::Service<tower_lsp::jsonrpc::Request>>::call::{{closure}}
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/tower-lsp-0.19.0/src/service.rs:124:31
  17: <core::pin::Pin<P> as core::future::future::Future>::poll
             at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/core/src/future/future.rs:125:9
  18: <F as futures_core::future::TryFuture>::try_poll
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/futures
-core-0.3.26/src/future.rs:82:9
  19: <futures_util::future::try_future::into_future::IntoFuture<Fut> as core::future::future::Future>::poll
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/futures-util-0.3.26/src/future/try_future/into_future.rs:34:9
  20: <futures_util::future::future::map::Map<Fut,F> as core::future::future::Future>::poll
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/futures-util-0.3.26/src/future/future/map.rs:55:37
  21: <futures_util::future::future::Map<Fut,F> as core::future::future::Future>::poll
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/futures-util-0.3.26/src/lib.rs:91:13
  22: <futures_util::future::try_future::UnwrapOrElse<Fut,F> as core::future::future::Future>::poll
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/futures-util-0.3.26/src/lib.rs:91:13
  23: <futures_util::stream::futures_unordered::FuturesUnordered<Fut> as futures_core::stream::Stream>::poll_next
             at ./.cargo/registry/src/g
ithub.com-1ecc6299db9ec823/futures-util-0.3.26/src/stream/futures_unordered/mod.rs:518:17
  24: futures_util::stream::stream::StreamExt::poll_next_unpin
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/futures-util-0.3.26/src/stream/stream/mod.rs:1625:9
  25: <futures_util::stream::stream::buffer_unordered::BufferUnordered<St> as futures_core::stream::Stream>::poll_next
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/futures-util-0.3.26/src/stream/stream/buffer_unordered.rs:75:15
  26: <futures_util::stream::stream::filter_map::FilterMap<St,Fut,F> as futures_core::stream::Stream>::poll_next
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/futures-util-0.3.26/src/stream/stream/filter_map.rs:79:47
  27: <futures_util::stream::stream::map::Map<St,F> as futures_core::stream::Stream>::poll_next
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/futures-util-0.3.26/src/stream/stream/map.rs:58:26
  28: <futures_util::stream::stream::fuse::Fuse<S> as 
futures_core::stream::Stream>::poll_next
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/futures-util-0.3.26/src/stream/stream/fuse.rs:53:27
  29: <futures_util::stream::stream::forward::Forward<St,Si,Item> as core::future::future::Future>::poll
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/futures-util-0.3.26/src/stream/stream/forward.rs:59:19
  30: <futures_util::stream::stream::Forward<St,Si> as core::future::future::Future>::poll
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/futures-util-0.3.26/src/lib.rs:91:13
  31: <futures_util::future::future::map::Map<Fut,F> as core::future::future::Future>::poll
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/futures-util-0.3.26/src/future/future/map.rs:55:37
  32: <futures_util::future::future::Map<Fut,F> as core::future::future::Future>::poll
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/futures-util-0.3.26/src/lib.rs:91:13
  33: <futures_util::future::maybe_done::Maybe
Done<Fut> as core::future::future::Future>::poll
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/futures-util-0.3.26/src/future/maybe_done.rs:95:38
  34: tower_lsp::transport::Server<I,O,L>::serve::{{closure}}::{{closure}}
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/futures-util-0.3.26/src/async_await/join_mod.rs:95:13
  35: <futures_util::future::poll_fn::PollFn<F> as core::future::future::Future>::poll
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/futures-util-0.3.26/src/future/poll_fn.rs:56:9
  36: tower_lsp::transport::Server<I,O,L>::serve::{{closure}}
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/tower-lsp-0.19.0/src/transport.rs:163:9
  37: ark::lsp::backend::start_lsp::{{closure}}
             at ./positron/extensions/positron-r/amalthea/crates/ark/src/lsp/backend.rs:609:52
  38: tokio::runtime::park::CachedParkThread::block_on::{{closure}}
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.26.0/src/r
untime/park.rs:283:63
  39: tokio::runtime::coop::with_budget
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.26.0/src/runtime/coop.rs:107:5
  40: tokio::runtime::coop::budget
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.26.0/src/runtime/coop.rs:73:5
  41: tokio::runtime::park::CachedParkThread::block_on
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.26.0/src/runtime/park.rs:283:31
  42: tokio::runtime::context::BlockingRegionGuard::block_on
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.26.0/src/runtime/context.rs:315:13
  43: tokio::runtime::scheduler::multi_thread::MultiThread::block_on
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.26.0/src/runtime/scheduler/multi_thread/mod.rs:66:9
  44: tokio::runtime::runtime::Runtime::block_on
             at ./.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.26.0/src/runtime/runtime.rs:304:45
  45: ark::lsp::backend::start_lsp

             at ./positron/extensions/positron-r/amalthea/crates/ark/src/lsp/backend.rs:610:5
  46: <ark::lsp::handler::Lsp as amalthea::language::lsp_handler::LspHandler>::start::{{closure}}
             at ./positron/extensions/positron-r/amalthea/crates/ark/src/lsp/handler.rs:51:31
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

[kevinushey]

Should now be fixed; this was caused by the document update events sent via VSCode being out-of-sync in some occasions. We now explicitly check the document version we receive, and delay applying those deltas if there appears to be a more recent update to be applied.