[psteinroe]

Addresses #446.

Why

tower-lsp has been unmaintained since August 2024. It also panics when the server sends a response after the client has disconnected (ebkalderon/tower-lsp#413, reported in #446). The panic happens in its transport:

// tower-lsp-0.20.0/src/transport.rs:116-121
let process_server_tasks = server_tasks_rx
    .buffer_unordered(self.max_concurrency)
    .filter_map(future::ready)
    .map(|res| Ok(Message::Response(res)))
    .forward(responses_tx.clone().sink_map_err(|_| unreachable!()))

Once writing to the client fails, print_output stops and drops the receiving end of responses_tx. The next request to finish then fails to send its response and lands in unreachable!().

The community fork tower-lsp-server is maintained and is what Biome's biome_lsp (where our LSP layer comes from) uses. In 0.23.0 the same line forwards into the channel without the unreachable!(), and a failed send just ends the stream:

// tower-lsp-server-0.23.0/src/transport.rs
let process_server_tasks = server_tasks_rx
    .buffer_unordered(self.max_concurrency)
    .filter_map(future::ready)
    .map(|res| Ok(Message::Response(res)))
    .forward(responses_tx.clone());

The fork also fixed a related panic in 0.21.1: "Do no panic when receiving a response whose request has been cancelled". I pinned 0.23.0 rather than the 0.24 RC, because the RC switches the types crate again.

What changed

The change is mechanical and limited to pgls_lsp. Only that crate depended on tower-lsp; pgls_wasm keeps its own lsp-types.

• tower-lsp = "0.20.0" → tower-lsp-server = "0.23.0". The tower dev-dependency used by the integration tests goes from 0.4 to 0.5 to match, which drops tower 0.4 from the lockfile.
• tower_lsp::lsp_types → tower_lsp_server::ls_types, and tower_lsp:: → tower_lsp_server::.
• #[tower_lsp::async_trait] is gone. LanguageServer now uses async fn in traits.
• Url → Uri. Uri wraps fluent_uri rather than the url crate:
  • to_file_path() now returns Option<Cow<Path>> instead of Result<PathBuf, ()>. The match arms in Session::file_path, Session::base_path, load_workspace_settings and did_change_watched_files are adapted, and the fallbacks are unchanged.
  • Uri doesn't implement Display, so tracing fields and log messages use uri.as_str(). That prints the same string as before.
  • Url::parse → Uri::from_str, for diagnostic code-description links and in the tests.
• New struct fields get their defaults: InitializeResult::offset_encoding: None is skipped when serialized, so the wire output is the same. The tests also set InitializeParams::work_done_progress_params.
• Custom methods (pgls/shutdown, pgls/set_configuration_overrides, and the workspace methods registered through workspace_method!) are registered through the same LspService::build(..).custom_method(..) API, which is unchanged.

Behaviour is meant to be identical. There are no feature changes.

Tests

• New client_disconnecting_mid_request_does_not_panic test in crates/pgls_lsp/tests/server.rs. It runs the server over in-memory pipes, drops the client's read end, sends a batch of requests, and checks that serve returns without panicking. I ran the same scenario in a scratch crate against tower-lsp 0.20, and it reproduces the panic: panicked at tower-lsp-0.20.0/src/transport.rs:120:60: internal error: entered unreachable code.
• All pgls_lsp tests pass against the docker DB, and so do all pgls_cli tests (including the daemon / lsp-proxy ones). cargo clippy --all-targets --all-features is clean.

Risks

• URI normalisation. url::Url normalised URIs it parsed (scheme case, percent-encoding of unsafe characters, and so on). fluent_uri keeps the client's string as is and rejects invalid URIs. Documents are keyed by the URI the client sends, and responses now echo that exact string, so a client that sends consistent URIs (every mainstream client does) sees no difference. A client that sends URIs that aren't RFC 3986 valid would now get a deserialization error where url would have repaired them.
• Windows paths. Uri::to_file_path builds Windows paths with / separators (z:/workspace/... instead of z:\workspace\...). std::path treats both the same, and Biome runs the same conversion on Windows.
• Merge conflicts. This touches every handler's imports, so it will conflict with the open feat(linter): add autofixes for lint rules #859 (code actions) and feat(lsp): add inlay hints and resolve hover through the catalog #861 (inlay hints handler). Whichever merges later rebases. The conflicts are the same lsp_types/Url renames.