#22: Custom LSP integration for the Monaco editor (Python & QASM)

[NicKIT01]

Summary

Adds full Language Server Protocol support to the monaco-react code editor from suren-atoyan.
Python and QASM files now get real IDE features (completion, hover,
diagnostics, ...) backed by embedded pylsp / qasmlsp binaries, bridged
to the browser over WebSockets.

• The new backend LSP module manages one operating system process per editor session. It acts as a proxy and forwards incoming JSON-RPC messages to the language server binaries via the stdio bridge.
• New frontend LSP layer (JsonRpcTransport, LSPClient,
  LSPClientManager) wires Monaco's language providers to these sessions,
  with debounced open/change/close lifecycle and reconnect handling.
• Docker images build and bundle both language servers; compose files and
  CI updated accordingly.

Backend (edu.kit.quak.*.lsp)

• core.lsp: domain model (LspLanguageId, LspServerDefinition, LspSessionId)
• application.lsp: LspSessionService orchestrates session lifecycle via ports (incoming ports: LspSessionServicePort; outgoing ports: LspSessionFactoryPort, LspSessionPort, LspServerRegistryPort, LspClientConnectionPort)
• infrastructure.lsp.out.process: ProcessLspSessionAdapter: one process per session, stdio JSON-RPC via StdioJsonRpcBridge, isolated per-session workspace directory; DefaultLspServerRegistry
• infrastructure.lsp.in.websocket: LspWebSocketHandler routes /lsp/{language} traffic to/from sessions; LspWebSocketExceptionHandler; WebSocketConfig
• infrastructure.lsp.config: LspProperties (quak.lsp.*) and LspServerStartupValidator (logs whether each configured server binary is reachable on startup)

Frontend

• lsp/JsonRpcTransport.ts: WebSocket-based JSON-RPC transport with reconnect/idle handling
• lsp/LSPClient.ts: per-language client; registers Monaco providers (completion, hover, diagnostics, ...) and manages document open/change/close with debounced change notifications
• lsp/LSPClientManager.ts: singleton managing one LSPClient per language, tracks active documents per editor group, debounced hide/dispose, reconnect backoff
• hooks/editor/useLSPSetup.ts (new) and updates to useEditorModelManager.ts, useEditorLanguage.ts, QLPEditor.tsx wire the editor's model lifecycle into the LSP layer

Lifecycle & capacity management

• quak.lsp.process.termination-timeout-ms (default 2000ms): Destroy/terminate lsp session - applied to the LSP process and any child processes
• quak.lsp.limits.max-processes (default 40) / max-processes-per-user (default 4): caps total and per-user concurrent LSP processes per backend instance (may be reset based on load tests and real world numbers)
• quak.lsp.websocket.session-idle-timeout-ms (default 15 min): idle WebSocket sessions are closed; the frontend automatically restores the connection on the next change
• Sessions are cleaned up consistently on normal close, client disconnect and server crash, releasing the corresponding capacity slot

Languages

• Python via pylsp (backend/lsp/servers/python)
• QASM via qasmlsp (backend/lsp/servers/qasm)
• Adding a new language requires no backend code changes — see backend/lsp/README.md

Deployment

• backend/Dockerfile builds both language servers in dedicated stages
• docker-compose.dev.yaml / docker-compose.prod.yaml: production mounts an isolated tmp-filesystem for per-session workspaces
• CI (test_and_build.yml) builds and bundles the LSP servers

Out of scope / possible follow-ups

• Metrics/observability for LSP process count and latency
• Load testing under concurrent multi-user sessions
• Possibly process warm-up/pooling to increase performance

[Jooshua]

Some minor comments

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[Jooshua]

Looks good now :)