mathworks / mathworks/MATLAB-language-server

Crash when client advertises `workspace/workspaceFolders` but doesn’t implement handler

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bug
Dominant language
TypeScript
Stars
125
Forks
21
PR merge metrics
No merged PRs in 30d

Description

Describe the bug

When a client advertises workspace.workspaceFolders but does not implement the workspace/workspaceFolders request, the server assumes success and later code dereferences a missing/failed result, causing a crash.

To Reproduce

  1. Start the server with a client that sets capabilities.workspace.workspaceFolders = true but does not handle workspace/workspaceFolders (e.g., powernap/crush).
  2. Complete initialize/initialized.
  3. The server requests workspace/workspaceFolders; the client returns a JSON-RPC error; the server crashes or becomes unstable.

Expected behavior

  • No crash. Treat request errors/null as no folders and continue.
  • Prefer InitializeParams.workspaceFolders when present and cache for later use.

Useful Information

  • MATLAB-language-server Version: v1.3.6
  • MATLAB Version: R2025b Update 1 (25.2.0.3042426) 64-bit (glnxa64)
  • OS Version: Ubuntu 24.04.3 LTS as devcontainer (mcr.microsoft.com/devcontainers/base:ubuntu-24.04) with MATLAB feature (ghcr.io/mathworks/devcontainer-features/matlab)
  • Language Server Client: crush v0.13.6
    • LSP Client Library: crush v0.13.6 uses powernap v0.0.0-20251015113943-25f979b54ad4

Additional context

  • Affected code: src/server.ts (capability gate), src/lifecycle/MatlabSession.ts (launch dir), src/lifecycle/PathSynchronizer.ts (on connect), src/indexing/WorkspaceIndexer.ts (index roots).
  • Repro: node build from source; ran /opt/matlab-language-server/out/index.js with the client above (crush).
  • Fix: defensively wrap all getWorkspaceFolders() calls; only enable PathSynchronizer if the request succeeds; fall back to InitializeParams.workspaceFolders or [] and log a warning when clients error.

I will be submitting a pull request.

Example traffic between `crush` and `matlab-langauge-server`
Example traffic between crush and matlab-langauge-server

stdin:

Content-Length: 2837

{"id":0,"jsonrpc":"2.0","method":"initialize","params":{"capabilities":{"general":{"markdown":{"parser":"marked","version":"1.1.0"},"positionEncodings":["utf-16"],"regularExpressions":{"engine":"ECMAScript","version":"ES2020"}},"textDocument":{"codeAction":{"codeActionLiteralSupport":{"codeActionKind":{"valueSet":["quickfix","refactor","refactor.extract","refactor.inline","refactor.rewrite","source","source.organizeImports"]}},"dataSupport":true,"dynamicRegistration":true,"isPreferredSupport":true,"resolveSupport":{"properties":["edit"]}},"completion":{"completionItem":{"commitCharactersSupport":true,"deprecatedSupport":true,"documentationFormat":["markdown","plaintext"],"insertReplaceSupport":true,"preselectSupport":true,"resolveSupport":{"properties":["documentation","detail","additionalTextEdits"]},"snippetSupport":false,"tagSupport":{"valueSet":[1]}},"contextSupport":true,"dynamicRegistration":true},"definition":{"dynamicRegistration":true,"linkSupport":true},"documentHighlight":{"dynamicRegistration":true},"documentSymbol":{"dynamicRegistration":true,"hierarchicalDocumentSymbolSupport":true},"formatting":{"dynamicRegistration":true},"hover":{"contentFormat":["markdown","plaintext"],"dynamicRegistration":true},"publishDiagnostics":{"codeDescriptionSupport":true,"dataSupport":true,"relatedInformation":true,"tagSupport":{"valueSet":[1,2]},"versionSupport":true},"rangeFormatting":{"dynamicRegistration":true},"references":{"dynamicRegistration":true},"rename":{"dynamicRegistration":true,"prepareSupport":true},"synchronization":{"didSave":true,"dynamicRegistration":true,"willSave":true,"willSaveWaitUntil":true}},"window":{"showDocument":{"support":true},"showMessage":{"messageActionItem":{"additionalPropertiesSupport":true}},"workDoneProgress":true},"workspace":{"applyEdit":true,"configuration":true,"didChangeConfiguration":{"dynamicRegistration":true},"didChangeWatchedFiles":{"dynamicRegistration":true,"relativePatternSupport":true},"fileOperations":{"didCreate":true,"didDelete":true,"didRename":true,"dynamicRegistration":true,"willCreate":true,"willDelete":true,"willRename":true},"symbol":{"dynamicRegistration":true},"workspaceEdit":{"documentChanges":true,"failureHandling":"textOnlyTransactional","normalizesLineEndings":true,"resourceOperations":["create","rename","delete"]},"workspaceFolders":true}},"clientInfo":{"name":"powernap","version":"0.1.0"},"initializationOptions":{"MATLAB":{"indexWorkspace":true,"installPath":"/opt/matlab/R2025b","matlabConnectionTiming":"onStart","prewarmGraphics":false,"signIn":true,"telemetry":false}},"locale":"en-us","processId":26471,"rootPath":"/workspaces/agentic-matlab-example","rootUri":"file:///workspaces/agentic-matlab-example","trace":"off","workspaceFolders":[{"uri":"file:///workspaces/agentic-matlab-example","name":"agentic-matlab-example"}]}}Content-Length: 52

{"jsonrpc":"2.0","method":"initialized","params":{}}Content-Length: 38

{"id":0,"result":null,"jsonrpc":"2.0"}Content-Length: 38

{"id":1,"result":[{}],"jsonrpc":"2.0"}Content-Length: 38

{"id":2,"result":null,"jsonrpc":"2.0"}Content-Length: 105

{"id":3,"error":{"code":0,"message":"no handler for method: workspace/workspaceFolders"},"jsonrpc":"2.0"}

stdout:

Content-Length: 134

{"jsonrpc":"2.0","method":"window/logMessage","params":{"type":4,"message":"(17:12:36) matlabls: Log Directory: /tmp/matlabls_26511"}}Content-Length: 583

{"jsonrpc":"2.0","id":0,"result":{"capabilities":{"codeActionProvider":true,"completionProvider":{"triggerCharacters":[".","("," ",",","/","\\"]},"definitionProvider":true,"documentFormattingProvider":true,"documentRangeFormattingProvider":true,"executeCommandProvider":{"commands":["matlabls.lint.suppress.line","matlabls.lint.suppress.file"]},"foldingRangeProvider":true,"referencesProvider":true,"signatureHelpProvider":{"triggerCharacters":["(",","]},"documentSymbolProvider":true,"renameProvider":{"prepareProvider":true},"documentHighlightProvider":true,"textDocumentSync":2}}}Content-Length: 201

{"jsonrpc":"2.0","id":0,"method":"client/registerCapability","params":{"registrations":[{"id":"91b68732-e3ec-49a1-bfb6-1202b45aad6f","method":"workspace/didChangeConfiguration","registerOptions":{}}]}}Content-Length: 101

{"jsonrpc":"2.0","id":1,"method":"workspace/configuration","params":{"items":[{"section":"MATLAB"}]}}Content-Length: 204

{"jsonrpc":"2.0","id":2,"method":"client/registerCapability","params":{"registrations":[{"id":"93246463-a499-485b-b7af-5c7110954b4d","method":"workspace/didChangeWorkspaceFolders","registerOptions":{}}]}}Content-Length: 103

{"jsonrpc":"2.0","method":"matlab/connection/update/server","params":{"connectionStatus":"connecting"}}Content-Length: 62

{"jsonrpc":"2.0","id":3,"method":"workspace/workspaceFolders"}

stderr:

(node:26511) [DEP0040] DeprecationWarning: The `punycode` module is deprecated. Please use a userland alternative instead.
(Use `node --trace-deprecation ...` to show where the warning was created)
/opt/matlab-language-server/out/index.js:43412
                        responsePromise.reject(new messages_1.ResponseError(error.code, error.message, error.data));
                                               ^

ResponseError: no handler for method: workspace/workspaceFolders
    at handleResponse (/opt/matlab-language-server/out/index.js:43412:48)
    at handleMessage (/opt/matlab-language-server/out/index.js:43192:13)
    at processMessageQueue (/opt/matlab-language-server/out/index.js:43209:17)
    at Immediate.<anonymous> (/opt/matlab-language-server/out/index.js:43181:13)
    at process.processImmediate (node:internal/timers:485:21) {
  code: 0,
  data: undefined
}

Node.js v22.21.1
Example `crush.json` lsp config for `matlab-language-server`
Example crush.json lsp config for matlab-language-server
{
  "$schema": "https://charm.land/crush.json",
  "lsp": {
    "matlab": {
      "command": "/usr/local/bin/matlab-language-server",
      "args": [
        "--stdio"
      ],
      "env": {
        "MLM_LICENSE_FILE": "27000@host"
      },
      "init_options": {
        "MATLAB": {
          "installPath": "/opt/matlab/R2025b",
          "indexWorkspace": true,
          "matlabConnectionTiming": "onStart",
          "telemetry": false,
          "signIn": true,
          "prewarmGraphics": false
        }
      }
    }
  },
  ...
}

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start in src/server.ts and trace workspace-folder handling through src/lifecycle/MatlabSession.ts, src/lifecycle/PathSynchronizer.ts, and src/indexing/WorkspaceIndexer.ts. Verify the reported error path with the provided client scenario and existing repository checks. Done means failed or null workspace-folder requests no longer crash the server, initialization folders are used when available, and later indexing continues with an empty fallback.

Written by the indexing model from the issue text.

Assessment

Tech stack
typescript
Domain
devtools
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Clearly specified
Newbie friendliness
42/100

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