fix(lsp): address review feedback on background init (#172)

- clear expected languages after init so a partially-failed language
  falls back to NoServerForLanguage instead of ServerInitializing forever
- log skipped non-object JSON at debug, not warn (OmniSharp bursts at startup)
- reword "wait a few seconds" -> "wait and retry / may take minutes" (error + docs)

Author: xlemaitre-poc

CHANGELOG.md

@@ -28,6 +28,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - **Initialize handshake timeout** — the LSP `initialize` request now honors the per-server `timeout_seconds` configuration instead of a hardcoded 30 s, so servers that need longer to load on large projects are no longer killed mid-initialization. (#172)
 - **Startup `null` messages** — the LSP receive loop skips bare `null`/non-object JSON-RPC messages (emitted by OmniSharp during startup) and keeps reading, instead of treating them as a fatal protocol error that drops the connection. (#172)
+- **Partial-success expected languages** — the "expected languages" set is cleared once background initialization completes, so a language whose server failed to spawn (when others succeeded) falls back to `NoServerForLanguage` instead of reporting `ServerInitializing` forever. (#172)
 
 - **ServerCancelled retry** — `LspClient::request()` now retries up to 3 times with exponential backoff (500 ms → 1 s → 2 s) when an LSP server returns error code -32802 with `data.retriggerRequest: true`, instead of propagating the error immediately to the MCP caller (#128)
 - **Integration test readiness gate** — Replaced `publishDiagnostics`-based readiness signal with hover-probe polling (3 consecutive successful hover responses required), matching the ra_e2e approach; fixes 3 of 5 integration tests that failed consistently in isolation after PR #123 (#127)

crates/mcpls-core/src/error.rs

@@ -66,7 +66,7 @@ pub enum Error {
 
     /// LSP server for the language is configured but still initializing.
     #[error(
-        "LSP server for language '{0}' is still initializing (large project load in progress); wait a few seconds and retry the request"
+        "LSP server for language '{0}' is still initializing (large project load in progress); wait and retry the request (this may take a few minutes on large projects)"
     )]
     ServerInitializing(String),
 

crates/mcpls-core/src/lib.rs

@@ -417,7 +417,13 @@ fn spawn_lsp_servers_background(
         let server_count = result.server_count();
         let notification_receivers = {
             let mut t = translator.lock().await;
-            register_servers(result, &mut t)
+            let receivers = register_servers(result, &mut t);
+            // Background initialization has completed; stop reporting "still
+            // initializing" (especially for languages whose server failed to
+            // spawn on partial success, which would otherwise return
+            // ServerInitializing forever instead of NoServerForLanguage).
+            t.clear_expected_languages();
+            receivers
         };
         info!("Proceeding with {} LSP server(s)", server_count);
 

crates/mcpls-core/src/lsp/transport.rs

@@ -13,7 +13,7 @@ use std::collections::HashMap;
 use serde_json::Value;
 use tokio::io::{AsyncBufReadExt, AsyncReadExt, AsyncWriteExt, BufReader};
 use tokio::process::{ChildStdin, ChildStdout};
-use tracing::{trace, warn};
+use tracing::{debug, trace, warn};
 
 use crate::error::{Error, Result};
 use crate::lsp::types::{InboundMessage, JsonRpcNotification, JsonRpcRequest, JsonRpcResponse};
@@ -111,7 +111,10 @@ impl LspTransport {
             // (or other non-object) JSON-RPC message. Skip it and read the next
             // framed message instead of killing the whole message loop.
             if !value.is_object() {
-                warn!("Skipping non-object LSP message: {}", value);
+                // Some servers (notably OmniSharp) emit a burst of these during
+                // startup; log at debug to avoid flooding the logs for what is a
+                // recoverable, expected condition.
+                debug!("Skipping non-object LSP message: {}", value);
                 continue;
             }
 

docs/user-guide/troubleshooting.md

@@ -233,7 +233,7 @@ mcpls --log-level debug
 roots = ["/Users/username/current-project"]
 ```
 
-**Note**: `timeout_seconds` also bounds the initial `initialize` handshake, so raising it (Solution 1) is what helps a server that needs minutes to load a large solution. While a configured server is still initializing, tool calls for that language return a "server is still initializing - wait a few seconds and retry" message rather than a hard "no server configured" error.
+**Note**: `timeout_seconds` also bounds the initial `initialize` handshake, so raising it (Solution 1) is what helps a server that needs minutes to load a large solution. While a configured server is still initializing, tool calls for that language return a "server is still initializing - wait and retry" message (loading a large solution may take a few minutes) rather than a hard "no server configured" error.
 
 ### "rust-analyzer indexing takes forever"